So I have been trying to implement a feature in my app where all the Posts will be listed to a recyclerView within a Fragment. However, whenever I access getActivity().getApplicationContext(), its returning null.
From what I understand is that getActivity will only return null if the fragment has been detached. I thought that my fragment hasn't been detached yet isince I'm opening it first time.
getActivity().getApplicationContext() is called inside HomeFragment.java.
Here is my code:
HomeFragment.java
public class HomeFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
List<Post> posts = new ArrayList<>();
private RecyclerView postsRecyclerView;
private HomePostsAdapter pAdapter;
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
//private Activity fragmentContext;
public HomeFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment HomeFragment.
*/
// TODO: Rename and change types and number of parameters
public static HomeFragment newInstance(String param1, String param2) {
HomeFragment fragment = new HomeFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
pAdapter = new HomePostsAdapter(posts);
RecyclerView.LayoutManager pLayoutManager = new LinearLayoutManager(getActivity().getApplicationContext());
postsRecyclerView = (RecyclerView) container.findViewById(R.id.homePostsRcyclerV);
postsRecyclerView.setLayoutManager(pLayoutManager);
postsRecyclerView.setItemAnimator(new DefaultItemAnimator());
postsRecyclerView.setAdapter(pAdapter);
populatePostsDetails();
pAdapter.notifyDataSetChanged();
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_home, container, false);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
private void populatePostsDetails() {
posts.add(new Post(1, "A Post: The First One", "Once upon a time, there was this useless app", "July"));
posts.add(new Post(2, "The Story begins today", "It was I the allfather who did it!", "July"));
posts.add(new Post(3, "Another POST!", "what is the point of this thing h8uh?", "July"));
posts.add(new Post(4, "Dandandan", "asdasdasdasdasdasdasdasdasdasd", "July"));
posts.add(new Post(5, "A Post: The First One", "Once upon a time, there was this useless app", "July"));
posts.add(new Post(6, "The Story begins today", "It was I the allfather who did it!", "July"));
posts.add(new Post(7, "Another POST!", "what is the point of this thing h8uh?", "July"));
posts.add(new Post(8, "Dandandan", "asdasdasdasdasdasdasdasdasdasd", "July"));
posts.add(new Post(9, "A Post: The First One", "Once upon a time, there was this useless app", "July"));
posts.add(new Post(10, "The Story begins today", "It was I the allfather who did it!", "July"));
posts.add(new Post(11, "Another POST!", "what is the point of this thing h8uh?", "July"));
posts.add(new Post(12, "Dandandan", "asdasdasdasdasdasdasdasdasdasd", "July"));
}
}
HomePostsAdapter.java
public class HomePostsAdapter extends RecyclerView.Adapter<HomePostsAdapter.CustomViewHolder>{
private List<Post> posts;
public class CustomViewHolder extends RecyclerView.ViewHolder {
public TextView pTitle, pContent;
public CustomViewHolder(View view) {
super(view);
pTitle = (TextView) view.findViewById(R.id.postTitle);
pContent = (TextView) view.findViewById(R.id.postContent);
}
}
public HomePostsAdapter(List<Post> posts){
this.posts = posts;
}
#Override
public CustomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext())
.inflate(R.layout.posts_list, parent, false);
return new CustomViewHolder(itemView);
}
#Override
public void onBindViewHolder(CustomViewHolder holder, int position) {
Post post = posts.get(position);
holder.pTitle.setText(post.getPostTitle());
holder.pContent.setText(post.getPostContent());
}
#Override
public int getItemCount() {
return posts.size();
}
}
Post.java
public class Post {
int id;
String title;
String content;
String date_created;
// sets values for the posts
public Post(int p_id, String p_title, String p_content, String p_date_created) {
this.id = p_id;
this.title = p_title;
this.content = p_content;
this.date_created = p_date_created;
}
public int getPostId() {
return this.id;
}
public String getPostTitle() {
return this.title;
}
public String getPostContent() {
return this.content;
}
public String getPostDateCreated() {
return this.date_created;
}
}
Any help will be greatly appreciated!
Logcat:
03-02 23:18:03.974 3377-3377/com.example.darkestmidnight.lykeyfoods E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.darkestmidnight.lykeyfoods, PID: 3377
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.example.darkestmidnight.lykeyfoods.activities.main_navigation.HomeFragment.onCreateView(HomeFragment.java:85)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2439)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1460)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:802)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:733)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Everything you're doing on onCreateView() (except for actually inflating the view), should be moved to onViewCreated(). You're calling container.findViewById(R.id.homePostsRcyclerV) before actually inflating or returning your layout - effectively looking for a RecyclerView in an empty container.
You should instead just return your newly inflated view in onCreateView() and move the logic acting on the view to onViewCreated(), where you are passed the View you just created.
Related
I'm new to android coding, I've tried all the possible solution here and on YouTube but still struggling. I just want how to match the data from a dialog of a fragment to another fragment upon pressing the button. we're working on a simple project. :)
Here is what we want to do.Kindly watch this link:
https://imgur.com/tGdWcfq
We want to change the name that will match the dialog upon clicking the "set parameters' button
here's what we found online the difference is we have a dialog button
https://www.youtube.com/watch?v=ZXoGG2XTjzU
https://www.youtube.com/watch?v=69C1ljfDvl0
Here are the codes
RecyclerViewAdapter.java
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder> {
Context mContext;
List<specieList> mData;
Dialog myDialog;
public RecyclerViewAdapter(Context mContext, List<specieList> mData) {
this.mContext = mContext;
this.mData = mData;
}
#Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v;
Button b;
v = LayoutInflater.from(mContext).inflate(R.layout.row,parent,false);
final MyViewHolder vHolder = new MyViewHolder(v);
myDialog = new Dialog(mContext);
myDialog.setContentView(R.layout.fishpop);
myDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
b = myDialog.findViewById(R.id.toasted);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
TextView toastfish = (TextView) myDialog.findViewById(R.id.dialog_fish_id);
Toast.makeText(mContext,"Parameters are now set for " + toastfish.getText().toString(), Toast.LENGTH_SHORT).show();
// here upon clicking this button click we want to match the details in this dialog to another tab. Kindly watch the link above :)
}
});
vHolder.fish_choices.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
TextView dialog_fish = (TextView) myDialog.findViewById(R.id.dialog_fish_id);
TextView dialog_sciname = (TextView) myDialog.findViewById(R.id.dialog_sciname_id);
ImageView dialog_image = (ImageView) myDialog.findViewById(R.id.dialog_image_id);
dialog_fish.setText(mData.get(vHolder.getAdapterPosition()).getFish());
dialog_sciname.setText(mData.get(vHolder.getAdapterPosition()).getSciname());
dialog_image.setImageResource(mData.get(vHolder.getAdapterPosition()).getImage());
myDialog.show();
}
});
return vHolder;
}
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.tv_fish.setText(mData.get(position).getFish());
holder.tv_sciname.setText(mData.get(position).getSciname());
holder.img.setImageResource(mData.get(position).getImage());
}
#Override
public int getItemCount() {
return mData.size();
}
public static class MyViewHolder extends RecyclerView.ViewHolder {
private LinearLayout fish_choices;
private TextView tv_fish;
private TextView tv_sciname;
private ImageView img;
public MyViewHolder(View itemView) {
super(itemView);
fish_choices = (LinearLayout) itemView.findViewById(R.id.choices);
tv_fish = (TextView) itemView.findViewById(R.id.textView1);
tv_sciname = (TextView) itemView.findViewById(R.id.textView2);
img = (ImageView) itemView.findViewById(R.id.image);
}
}
}
Code for overview tab(This tab we want to match the content)
public class overview extends Fragment {
View v2;
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public overview() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment overview.
*/
// TODO: Rename and change types and number of parameters
public static overview newInstance(String param1, String param2) {
overview fragment = new overview();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
v2 = inflater.inflate(R.layout.fragment_overview, container, false);
Calendar calendar = Calendar.getInstance();
SimpleDateFormat time = new SimpleDateFormat("HH:mm:ss");
String currentDate = DateFormat.getDateInstance(DateFormat.FULL).format(calendar.getTime());
String currentTime = time.format(calendar.getTime());
TextView textViewDate =(TextView) v2.findViewById(R.id.date_id);
textViewDate.setText(currentDate);
TextView textViewTime =(TextView) v2.findViewById(R.id.time_id);
textViewTime.setText(currentTime);
return v2;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
Code for Specie tab (this tab we want to refer)
public class specie extends Fragment {
View v;
private RecyclerView myrecyclerview;
private List<specieList> lstspecie;
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public specie() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment specie.
*/
// TODO: Rename and change types and number of parameters
public static specie newInstance(String param1, String param2) {
specie fragment = new specie();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
lstspecie = new ArrayList<>();
lstspecie.add(new specieList("Nile Tilapia", "Oreochromis niloticus", R.drawable.tilapia));
lstspecie.add(new specieList("Ayungin (Silver Perch)", "Bidyanus bidyanus", R.drawable.ayungin));
lstspecie.add(new specieList("Sugpo (Tiger Prawn)", "Penaeus monodon", R.drawable.hipon));
lstspecie.add(new specieList("Hito (Catfish)", "Siluriformes", R.drawable.hito));
lstspecie.add(new specieList("Giant Gourami", "Osphronemus goramy", R.drawable.giant));
lstspecie.add(new specieList("Bangus (Milkfish)", "Chanos chanos", R.drawable.bangus));
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
v = inflater.inflate(R.layout.fragment_specie, container, false);
myrecyclerview = (RecyclerView)v.findViewById(R.id.specie_recycleview);
RecyclerViewAdapter recyclerAdapter = new RecyclerViewAdapter(getContext(), lstspecie);
myrecyclerview.setLayoutManager(new LinearLayoutManager(getActivity()));
myrecyclerview.setAdapter(recyclerAdapter);
return v;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
Thank you!
Using object oriented Approach
You can write a function in your activity and you can call a fragment's method from it, as you have your Fragment's reference in your Activity when you initialized it like
In Your Activity
class yourActivity ... {
// your other methods
public void callFragmentMethod(String params) {
// here call your fragment's method
fragment.method(params);
}
}
In your Fragment now
class yourFragment ... {
// your other methods
public void method(String params) {
// here call your fragment's method
here do whatever you want to do it with params
}
}
Now you can call your Activity's method either from another fragment or from Adapter, whatever you want
From Fragment you can call like
((yourActivity)getActivity()).callFragmentMethod(params);
From Adapter
((yourActivity)context).callFragmentMethod(params);
Call below method on your button click..
public void replaceFragment(Fragment fragment) {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction =
fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frameContainer, fragment);
fragmentTransaction.addToBackStack(fragment.toString());
fragmentTransaction.commit();
}
pass frameContainer in constructor of your Adapter like..
new RecyclerViewAdapter(context, list, R.id.frameContainer);
I am currently working on a project in which I have text data retrieved from a web page displayed between 3 different tabs declared as fragments.
There's a button refresh at the bottom of each tab & whenever the user presses that button, the app retrieves the most recent data from the web site & displays it in one of the three tabs.
The logic on which the app chooses the tab to write the text into is the following:
Write data into Tab 1 (leftmost). If Tab 1 already contains data, write into Tab 2. If Tab 2 already contains data, write into Tab 3. If all tabs contain data, overwrite data in Tab 1 & start the cycle over.
Here is my code before getting into my problem. I am only posting the relevant code to avoid flooding this message.
MainActivity:
public class MainActivity extends AppCompatActivity implements
Tab1.OnFragmentInteractionListener, Tab2.OnFragmentInteractionListener,
Tab3.OnFragmentInteractionListener{
final static String url = "http://159.203.78.94/rpilog/weatherstation.txt";
public static TextView dataTextTab1;
public static TextView dataTextTab2;
public static TextView dataTextTab3;
static Context context;
public static TabLayout tabLayout;
public static int tabPosition;
public static boolean tab1Used = false;
public static boolean tab2Used = false;
public static boolean tab3Used = false;
public static int positionFactor = -1;
static String TAG;
public static String dataFromURL;
public static TextView test;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Text placeholders for the data received from the URL.
dataTextTab1 = (TextView) findViewById(R.id.dataTextTab1);
dataTextTab2 = (TextView) findViewById(R.id.dataTextTab2);
dataTextTab3 = (TextView) findViewById(R.id.dataTextTab3);
context = getApplicationContext();
//Creating the tabs.
tabLayout = (TabLayout) findViewById(R.id.tablayout);
tabLayout.addTab(tabLayout.newTab().setText("No data"));
tabLayout.addTab(tabLayout.newTab().setText("No data"));
tabLayout.addTab(tabLayout.newTab().setText("No data"));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
//ViewPager & PagerAdapter object to allow sliding tabs.
final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
final PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
viewPager.setAdapter(adapter);
viewPager.setOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
public static void receiveString(){
RequestQueue queue = Volley.newRequestQueue(context);
//Requests a string response from the provided URL.
StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
dataFromURL = response;
if (positionFactor * 169 + 16 + 3 + 144 <= response.length()) {
if(tab1Used == false) {
tabPosition = 0;
TabLayout.Tab currentTab = tabLayout.getTabAt(tabPosition);
currentTab.setText(response.substring(positionFactor * 169, positionFactor * 169 + 16));
dataTextTab1.setText(response.substring(positionFactor * 169 + 16 + 3, positionFactor * 169 + 16 + 3 + 144));
tab1Used = true;
Log.e(TAG, "1ST TAB REACHED");
}
else if(tab1Used == true && tab2Used == false){
tabPosition = 1;
TabLayout.Tab currentTab = tabLayout.getTabAt(tabPosition);
currentTab.setText(response.substring(positionFactor * 169, positionFactor * 169 + 16));
dataTextTab2.setText(response.substring(positionFactor * 169 + 16 + 3, positionFactor * 169 + 16 + 3 + 144));
tab2Used = true;
Log.e(TAG, "2ND TAB REACHED");
}
else if(tab1Used == true && tab2Used == true && tab3Used == false){
tabPosition = 2;
TabLayout.Tab currentTab = tabLayout.getTabAt(tabPosition);
currentTab.setText(response.substring(positionFactor * 169, positionFactor * 169 + 16));
dataTextTab3.setText(response.substring(positionFactor * 169 + 16 + 3, positionFactor * 169 + 16 + 3 + 144));
tab3Used = true;
Log.e(TAG, "3RD TAB REACHED");
}
if(tab1Used == true && tab2Used == true && tab3Used == true){ //If there's data in all tabs => overwrite oldest.
tabPosition = 0;
TabLayout.Tab currentTab = tabLayout.getTabAt(tabPosition);
currentTab.setText(response.substring(positionFactor * 169, positionFactor * 169 + 16));
dataTextTab1.setText(response.substring(positionFactor * 169 + 16 + 3, positionFactor * 169 + 16 + 3 + 144));
Log.e(TAG, "1ST TAB OVER AGAIN");
tab2Used = false;
tab3Used = false;
}
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(context, "Error in data retrieval", Toast.LENGTH_LONG).show();
}
});
queue.add(stringRequest);
}
public void refresh(View view){ //Refresh action for FAB = onClick fct.
MainActivity.positionFactor++;
Toast.makeText(context, "Page refreshed", Toast.LENGTH_SHORT).show();
receiveString();
}
#Override
public void onFragmentInteraction(Uri uri) {
}
public static void showInfoPopup() { //Show popup info = onClick fct.
if (Menu.infoPopupDialog != null) {
Menu.infoPopupDialog.setContentView(R.layout.popup_layout);
Menu.infoPopupDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
Menu.infoPopupDialog.show();
}
}
public static void showLocationPopup(){ //Show popup location = onClick fct.
if(Menu.locationPopupDialog != null){
Menu.locationPopupDialog.setContentView(R.layout.popup_location);
Menu.locationPopupDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
Menu.locationPopupDialog.show();
}
}
PagerAdapter:
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNoOfTabs;
public PagerAdapter(FragmentManager fm, int numberOfTabs){
super(fm);
this.mNoOfTabs = numberOfTabs;
}
#Override
public Fragment getItem(int position) {
switch(position){
case 0:
Tab1 tab1 = new Tab1();
return tab1;
case 1:
Tab2 tab2 = new Tab2();
return tab2;
case 2:
Tab3 tab3 = new Tab3();
return tab3;
default:
return null;
}
}
#Override
public int getCount() {
return mNoOfTabs;
}
}
Tab1:
public class Tab1 extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public Tab1() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment Tab1.
*/
// TODO: Rename and change types and number of parameters
public static Tab1 newInstance(String param1, String param2) {
Tab1 fragment = new Tab1();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_tab1, container, false);
MainActivity.dataTextTab1 = rootView.findViewById(R.id.dataTextTab1);
return rootView;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
Tab2:
public class Tab2 extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public Tab2() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment Tab2.
*/
// TODO: Rename and change types and number of parameters
public static Tab2 newInstance(String param1, String param2) {
Tab2 fragment = new Tab2();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_tab2, container, false);
MainActivity.dataTextTab2 = rootView.findViewById(R.id.dataTextTab2);
return rootView;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
Tab3:
public class Tab3 extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public Tab3() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment Tab3.
*/
// TODO: Rename and change types and number of parameters
public static Tab3 newInstance(String param1, String param2) {
Tab3 fragment = new Tab3();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_tab3, container, false);
MainActivity.dataTextTab3 = rootView.findViewById(R.id.dataTextTab3);
return rootView;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:orientation="vertical"
android:layout_height="match_parent"
tools:context="com.myapps.toualbiamine.weathertracker.MainActivity">
<!--<android.support.v7.widget.Toolbar-->
<!--android:id="#+id/toolbar"-->
<!--android:layout_width="match_parent"-->
<!--android:layout_height="50dp"-->
<!--android:background="#color/colorPrimary"-->
<!--android:minHeight="?attr/actionBarSize"-->
<!--android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"-->
<!--app:popupTheme="#style/ThemeOverlay.AppCompat.Light">-->
<!--<TextView-->
<!--android:layout_width="wrap_content"-->
<!--android:layout_height="wrap_content"-->
<!--android:text="Swipe to switch tabs"-->
<!--android:textSize="30dp"/>-->
<!--</android.support.v7.widget.Toolbar>-->
<android.support.design.widget.TabLayout
android:id="#+id/tablayout"
android:layout_width="match_parent"
android:layout_height="30dp"
android:background="#color/textColor"
android:minHeight="?attr/actionBarSize"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
</android.support.design.widget.TabLayout>
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:id="#+id/pager"
android:background="#color/background">
</android.support.v4.view.ViewPager>
</LinearLayout>
fragment_tab3.xml - fragment_tab1.xml & fragment_tab2.xml are simple copies:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.myapps.toualbiamine.weathertracker.Tab1"
android:orientation="vertical"
android:layout_weight="1"
android:background="#drawable/bg"
android:backgroundTintMode="multiply"
android:backgroundTint="#color/background">
<!-- TODO: Update blank fragment layout -->
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Data"
android:textSize="40dp"
android:layout_gravity="center"
android:layout_marginTop="40dp"
android:textColor="#color/titleColor" />
<TextView
android:id="#+id/dataTextTab3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="120dp"
android:text="Data will come here"
android:textSize="15dp"
android:layout_gravity="center"
/>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.FloatingActionButton
android:id="#+id/floatingActionButton4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:layout_marginBottom="28dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:clickable="true"
app:backgroundTint="#color/background"
app:fabSize="normal"
app:srcCompat="#drawable/ic_refresh_black_24dp"
android:onClick="refresh"/>
</RelativeLayout>
</LinearLayout>
So, I've been trying to figure out a way around my problem & have done a lot of reading but I've been stuck here for now a week & it's the last part of my project.
Here is the issue. You can see that in my MainActivity class, in the method receiveString(), there is the following line:
dataTextTab3.setText(response.substring(positionFactor * 169 + 16 + 3, positionFactor * 169 + 16 + 3 + 144));
I used the same line for my two other TextViews dataTextTab1 & dataTextTab2 a few lines before in this same method.
This is the part where I parse the data that I want received from the website. The numbers correspond to a formula to determine the indexes of the substring I set the text to.
It works perfectly fine for my two other TextViews but when I reach the third TextView, dataTextTab3, I get a NullPointerException & I can't get my head around it to figure it out.
StackTrace:
E/AndroidRuntime: FATAL EXCEPTION: main Process:
com.myapps.toualbiamine.weathertracker, PID: 22340
java.lang.NullPointerException: Attempt to invoke virtual method
'void android.widget.TextView.setText(java.lang.CharSequence)' on a
null object reference
at com.myapps.toualbiamine.weathertracker.MainActivity$2.
onResponse(MainActivity.java:139) at
com.myapps.toualbiamine.weathertracker.MainActivity$2
.onResponse(MainActivity.java:108) at
com.android.volley.toolbox.StringRequest.
deliverResponse(StringRequest.java:60) at
com.android.volley.toolbox.StringRequest.
deliverResponse(StringRequest.java:30) at
com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.
run(ExecutorDelivery.java:99) at
android.os.Handler.handleCallback(Handler.java:790) at
android.os.Handler.dispatchMessage(Handler.java:99) at
android.os.Looper.loop(Looper.java:164) at
android.app.ActivityThread.main(ActivityThread.java:6494) at
java.lang.reflect.Method.invoke(Native Method) at
com.android.internal.os.RuntimeInit$MethodAndArgsCaller.
run(RuntimeInit.java:438) at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
One more thing, I get that error if I refresh 3 times from the first tab to logically fill all the tabs at once, however, if I refresh the first tab, then go to the second one & refresh it, and then go to the third one & refresh it, I do not get the NullPointerException.
Is there a way to avoid that NPE whatever happens? I would like to make sure that the user can refresh 3 times from the first tab without having the app crashing.
Thank you very much, Community! Please, I place a lot of hope into you right now, be the hero I need.
PSA: not duplicate of "why am I getting a NPE" since I went through most of the posts & I am explicitly declaring and instantiating my variables.
When you start the MainActivity, typically it will instantiate the visible Fragment (tab1) and the next one over (tab2) but not beyond that until you switch tabs. That happens later, after you have already called onCreate. That means that in your onCreate you are getting null for dataTextTab3
You shouldn't be holding references in your activity to views in Fragments, since as they are not guaranteed to exist all the time.
If you want to force them to exist, you can call viewPager.setOffscreenPageLimit(3); to allow more off-screen fragments to be instantiated at startup.
I have an odd situation, I have an Activity hosting a TabLayout/Viewpager that populates data based on changes to a Firebase Database. Unfortunately, the RecyclerView is not being populated, and I am receiving the error below in my logcat. I believe the fragment is being loaded even when it is not on screen, which is causing an error in the population of the RecyclerView. It is also weird as the RecyclerView does populate when I rotate the screen:
12-13 21:31:40.013 12490-12490/com.troychuinard.fanpolls E/RecyclerView: No adapter attached; skipping layout
Here is the ViewPager Adapter I have in my host Activity:
public class SectionPagerAdapter extends FragmentPagerAdapter {
public SectionPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new TrendingFragment();
case 1:
return new FollowingFragment();
case 2:
return new LiveFragment();
default:
return new TrendingFragment();
}
}
#Override
public int getCount() {
return 3;
}
#Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return getResources().getString(R.string.trending_text);
case 1:
return getResources().getString(R.string.following_text);
case 2:
return getResources().getString(R.string.new_text);
default:
return getResources().getString(R.string.trending_text);
}
}
}
Here is the complete fragment where I initialize the RecyclerView inside onCreateView() function in my LiveFragment, which is tab 3 in the TabLayout:
public class LiveFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private RecyclerView mRecyclerview;
private DatabaseReference mBaseRef;
private DatabaseReference mPollsRef;
private LinearLayoutManager mLayoutManager;
private FirebaseRecyclerAdapter <Poll, PollHolder> mFireAdapter;
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public LiveFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment LiveFragment.
*/
// TODO: Rename and change types and number of parameters
public static LiveFragment newInstance(String param1, String param2) {
LiveFragment fragment = new LiveFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mBaseRef = FirebaseDatabase.getInstance().getReference();
mPollsRef = mBaseRef.child("Polls");
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
final View v = inflater.inflate(R.layout.fragment_new, container, false);
Log.v("TAG", "ON CREATE CALLED FROM NEW");
mLayoutManager = new LinearLayoutManager(getActivity());
mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
mRecyclerview = (RecyclerView)v.findViewById(R.id.new_RecyclerView);
if (mRecyclerview != null){
mRecyclerview.setHasFixedSize(true);
}
if (mRecyclerview == null){
Log.v("TAG", "RECYCLERVIEW NULL");
} else if (mLayoutManager == null){
Log.v("TAG", "LAYOUTMANAGER NULL");
} else if (mFireAdapter == null) {
Log.v("TAG", "mFIREADAPTER NULL");
}
return v;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onStart() {
super.onStart();
}
#Override
public void onStop() {
super.onStop();
if (mFireAdapter != null){
mFireAdapter.cleanup();
}
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mRecyclerview.setLayoutManager(mLayoutManager);
mFireAdapter = new FirebaseRecyclerAdapter<Poll, PollHolder>(Poll.class, R.layout.latest_item, PollHolder.class, mPollsRef) {
#Override
protected void populateViewHolder(PollHolder viewHolder, Poll model, int position) {
viewHolder.mPollQuestion.setText(model.getQuestion());
Picasso.with(getActivity().getApplicationContext())
.load(model.getImage_URL())
.fit()
.into(viewHolder.mPollImage);
Log.v("QUESTION", model.getQuestion());
Log.v("IMAGE", model.getImage_URL());
}
};
mRecyclerview.setAdapter(mFireAdapter);
mPollsRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot x : dataSnapshot.getChildren()){
mFireAdapter.notifyItemInserted(0);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public static class PollHolder extends RecyclerView.ViewHolder {
TextView mPollQuestion;
ImageView mPollImage;
public PollHolder(View itemView) {
super(itemView);
mPollQuestion = (TextView) itemView.findViewById(R.id.latest_item_question);
mPollImage = (ImageView) itemView.findViewById(R.id.pollThumbNailImage);
}
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
Move your Adapter from onCreateView to onActivityCreated method after you have read data from firebase.
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
//read Poll data from firebase mPollsRef for example
//.... database reference to firebase
//Query mPollsRef = databaseReference.child("pools").limitToFirst(200);
mRecyclerview.setLayoutManager(mLayoutManager);
mFireAdapter = new FirebaseRecyclerAdapter<Poll, PollHolder>(Poll.class, R.layout.latest_item, PollHolder.class, mPollsRef) {
#Override
protected void populateViewHolder(PollHolder viewHolder, Poll model, int position) {
viewHolder.mPollQuestion.setText(model.getQuestion());
Picasso.with(getActivity().getApplicationContext())
.load(model.getImage_URL())
.fit()
.into(viewHolder.mPollImage);
Log.v("QUESTION", model.getQuestion());
Log.v("IMAGE", model.getImage_URL());
}
};
mRecyclerview.setAdapter(mFireAdapter);
}
My code for initialize Pager at HostActivity.java
private FragmentPagerAdapter mPagerAdapter;
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_absence);
// Create the adapter that will return a fragment for each section
mPagerAdapter = new FragmentPagerAdapter(getSupportFragmentManager()) {
private final Fragment[] mFragments = new Fragment[] {
new MyAbsenceFragment(),
new MyAttendanceFragment(),
new AbsTypesFragment(),
new LiveFragment(),
};
private final String[] mFragmentNames = new String[] {
"Absences",
"Attendances",
"AbsTypes",
"Live"
};
#Override
public Fragment getItem(int position) {
return mFragments[position];
}
#Override
public int getCount() {
return mFragments.length;
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentNames[position];
}
};
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mPagerAdapter);
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
I have a non activity class where I want to access my sharedpreferences I saved in a fragment. I can use these prefs in other fragments / activities, so they are working. When I try to assign the prefvalues to variables in my non_Activity class I always get a nullpointerexception no matter what I changed (I´ve read through mulitple topics here on stack on nothing worked).
public class VorgangDataSource {
Context mcontext;
float lbcount;
float rbcount;
float bcount;
SharedPreferences sharedPreferences;
SharedPreferences sharedPreferences1;
SharedPreferences sharedPreferences2;
private static final String LOG_TAG = VorgangDataSource.class.getSimpleName();
public SQLiteDatabase database;
private VorgangDbHelper dbHelper;
private String[] columns = {
VorgangDbHelper.COLUMN_ID,
VorgangDbHelper.COLUMN_START,
VorgangDbHelper.COLUMN_STOP,
VorgangDbHelper.COLUMN_LEFTB,
VorgangDbHelper.COLUMN_RIGHTB,
VorgangDbHelper.COLUMN_BOTTLE
};
public VorgangDataSource(Context context) {
Log.d(LOG_TAG, "DataSource erzeugt dbHelper!");
dbHelper = VorgangDbHelper.getInstance();
this.mcontext = context;
this.sharedPreferences = mcontext.getSharedPreferences("FILELB",Context.MODE_PRIVATE);
this.sharedPreferences1 = mcontext.getSharedPreferences("FILERB",Context.MODE_PRIVATE);
this.sharedPreferences2 = mcontext.getSharedPreferences("FILEBO",Context.MODE_PRIVATE);
this.lbcount = sharedPreferences.getFloat("KEYLB",0);
this.rbcount = sharedPreferences1.getFloat("KEYRB",0);
this.bcount = sharedPreferences2.getFloat("KEYBO",0);
}
public void open() {
Log.d(LOG_TAG, "Eine Referenz auf die Datenbank wird jetzt angefragt.");
database = dbHelper.getWritableDatabase();
Log.d(LOG_TAG, "Datenbank-Referenz erhalten. Pfad zur Datenbank: " + database.getPath());
}
public void close() {
dbHelper.close();
Log.d(LOG_TAG, "Datenbank mit Hilfe des DbHelpers geschlossen.");
}
public VorgangDataSource open(boolean readOnly) throws SQLException {
dbHelper = VorgangDbHelper.getInstance();
if(readOnly)
database = dbHelper.getReadableDatabase();
else
database = dbHelper.getWritableDatabase();
return this;
}
}
Error Log:
06-15 08:28:47.816 12806-12806/com.example... E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example PID: 12806
java.lang.NullPointerException
at com.example...VorgangDataSource.<init>(VorgangDataSource.java:169)
at com.example...frag_anzeigen.<init>(frag_anzeigen.java:53)
at com.example...MainActivity.onNavigationItemSelected(MainActivity.java:117)
at android.support.design.widget.NavigationView$1.onMenuItemSelected(NavigationView.java:151)
at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:811)
at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:958)
at android.support.design.internal.NavigationMenuPresenter$1.onClick(NavigationMenuPresenter.java:318)
at android.view.View.performClick(View.java:4748)
at android.view.View$PerformClick.run(View.java:19535)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5679)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
fragment-class
public class frag_anzeigen extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
private static final String TAG = frag_anlegen.class.getSimpleName();
private static final String FILENAME = TAG + ".kdf";
private List valueList = new ArrayList <String>();
final VorgangDataSource dataSource = new VorgangDataSource(getActivity());
ArrayAdapter<vorgangsdaten> VorgangArrayAdapter;
List<vorgangsdaten> vorgangsdatenList;
public frag_anzeigen() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment frag_anzeigen.
*/
// TODO: Rename and change types and number of parameters
public static frag_anzeigen newInstance(String param1, String param2) {
frag_anzeigen fragment = new frag_anzeigen();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View anzeigen = inflater.inflate(R.layout.frag_anzeigen,container,false);
anzeigen.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
if(event.getAction()==MotionEvent.ACTION_DOWN)
{
close();
}
return true;
}
});
Log.d(TAG,"Die Datenquelle wird geöffnet!");
dataSource.open();
vorgangsdatenList = dataSource.getAllVorgangsDaten();
VorgangArrayAdapter = new ArrayAdapter< >(getActivity(),R.layout.mylistlayout,vorgangsdatenList);
final ListView lv = (ListView)anzeigen.findViewById(R.id.listView);
lv.setAdapter(VorgangArrayAdapter);
//lv.setItemsCanFocus(false);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, final int position, final long id) {
String s_id = String.valueOf(id);
Log.d(s_id,"id_in_onitem");
String p_id = String.valueOf(position);
Log.d(p_id,"position_on_item");
final AlertDialog delete = new AlertDialog.Builder(getActivity()).create();
delete.setTitle(getResources().getString(R.string.advice));
delete.setMessage(getResources().getString(R.string.delete2dialog));
delete.setIcon(R.drawable.warning);
delete.setButton(DialogInterface.BUTTON_POSITIVE, getResources().getString(R.string.ok), new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
vorgangsdatenList.remove(position);
dataSource.deleteRow(id);
VorgangArrayAdapter.notifyDataSetChanged();
Toast.makeText(getActivity(), getResources().getString(R.string.eventdeleted), Toast.LENGTH_SHORT).show();
}
});
delete.setButton(DialogInterface.BUTTON_NEGATIVE, getResources().getString(R.string.cancel), new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
delete.closeOptionsMenu();
}
});
delete.show();
}
});
return anzeigen;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p/>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
#Override
public void onDestroyView() {
super.onDestroyView();
}
public void close (){
FragmentManager fm = getFragmentManager();
FragmentTransaction transaction = fm.beginTransaction();
transaction.setCustomAnimations(R.anim.slide_in_up,R.anim.slide_out_up);
transaction.remove(this);
transaction.commit();
}
}
The problem is in this line
final VorgangDataSource dataSource = new VorgangDataSource(getActivity());
Here getActivity() returns null because if onAttach isn't called yet of the respective fragment. So remove that line from there and write in onAttach method or onCreate method of fragment class.
Hope this will help you.
I'm trying to use an ArrayList to store an array of objects and then pass them to my adapter.
public ArrayList<Song> arrayOfSongs;
public SongsAdapter adapter;
I initially just declare my arrayofSongs. Then I initialize inside onCreateView() in my fragment
arrayOfSongs = new ArrayList<>();
adapter = new SongsAdapter(getContext(), arrayOfSongs);
The problem is that variable is initally null, and that gave me a lot of problems when I tried to use the adapter to populate the views initially. So I had to override my adapter's getView to return 0 if the array was null as suggested. Some comments told me that it was better just to "initialize an empty ArrayList to put into the adapter instead of using a null check inside of the adapter". How would I do this because I'm getting a null pointer exception when I call adapter.clear()
here is my SearchFragment
public class SearchFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public SearchFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment SearchFragment.
*/
// TODO: Rename and change types and number of parameters
public static SearchFragment newInstance(String param1, String param2) {
SearchFragment fragment = new SearchFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
public EditText editText;
public ImageButton searchButton;
public ProgressBar pb;
public ListView lv;
public ArrayList<Song> arrayOfSongs;
public SongsAdapter adapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View rootView = inflater.inflate(R.layout.fragment_search, container, false);
arrayOfSongs = new ArrayList<>();
adapter = new SongsAdapter(getContext(), arrayOfSongs);
editText = (EditText) rootView.findViewById(R.id.edit_message);
searchButton = (ImageButton) rootView.findViewById(R.id.search_button);
lv = (ListView) rootView.findViewById(R.id.listView);
lv.setAdapter(adapter);
pb = (ProgressBar) rootView.findViewById(R.id.progressBar);
pb.setIndeterminate(true);
pb.setVisibility(ProgressBar.INVISIBLE);
searchButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String searchWords = editText.getText().toString();
if (!searchWords.matches(""))
hitItunes(searchWords);
}
});
editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
#Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
boolean handled = false;
if (actionId == EditorInfo.IME_ACTION_SEARCH) {
String searchWords = editText.getText().toString();
if (!searchWords.matches("")) {
hitItunes(searchWords);
handled = true;
}
}
return handled;
}
});
return rootView;
}
public void hitItunes(String searchWords) {
pb.setVisibility(ProgressBar.VISIBLE);
try {
String url = "https://itunes.apple.com/search?term=" + URLEncoder.encode(searchWords, "UTF-8") + "&country=US&media=music&limit=100";
JsonObjectRequest req = new JsonObjectRequest(url, null,
new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject response) {
try {
VolleyLog.v("Response:%n %s", response.toString(4));
Log.d("volley_success", response.toString());
pb.setVisibility(ProgressBar.INVISIBLE);
JSONArray songsJSON = response.getJSONArray("results");
ArrayList<Song> songs = Song.fromJSON(songsJSON);
adapter.clear();
adapter.addAll(songs);
adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
VolleyLog.e("Error: ", error.getMessage());
Log.d("volley_error", error.getMessage());
}
});
/*
RequestQueue reqQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
reqQueue.add(req);
*/
try {
// add the request object to the queue to be executed
ApplicationController.getInstance().addToRequestQueue(req);
} catch (NullPointerException npe) {
npe.printStackTrace();
}
} catch (UnsupportedEncodingException uee) {
throw new AssertionError("UTF-8 is unknown");
}
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
/*
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
*/
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p/>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
and here is my logcat
03-23 12:12:08.678 2574-2574/com.loomius.loomius E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.loomius.loomius, PID: 2574
java.lang.NullPointerException
at android.widget.ArrayAdapter.clear(ArrayAdapter.java:258)
at com.loomius.loomius.SearchFragment$3.onResponse(SearchFragment.java:159)
at com.loomius.loomius.SearchFragment$3.onResponse(SearchFragment.java:148)
at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65)
at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5113)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
at dalvik.system.NativeStart.main(Native Method)
here is the SongsAdapter
public class SongsAdapter extends ArrayAdapter<Song> {
ArrayList<Song> mList;
Context mContext;
public SongsAdapter(Context context, ArrayList<Song> songs) {
super(context, 0, songs);
mList = songs;
mContext = context;
}
#Override
public int getCount() {
if(mList==null) {
return 0;
}
else {
return mList.size();
}
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
Song song = getItem(position);
if (convertView == null)
convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_song, parent, false);
TextView artistName = (TextView) convertView.findViewById(R.id.artistName);
TextView trackName = (TextView) convertView.findViewById(R.id.trackName);
artistName.setText(song.getArtist());
trackName.setText(song.getTitle());
return convertView;
}
}
You can solve this by
before calling adapter.clear() check it contains data or not using adapter.getCount()
if(adapter.getCount()>0)
adapter.clear()