We Keep Coding

Null Pointer Exception on an EditText in a Fragment [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 3 years ago.
I am building a signUp page in which i want a date picker but whenever i click on User Fragment to open Sign up Page then the app crashes, and the error is nullPointerException in EditText. Please Help me to solve it.
Here is the Code of UserFragment.java
public class UserFragment extends Fragment {
public EditText et_Date;
public static final int REQUEST_CODE = 11;
String selectedDate;
private OnFragmentInteractionListener mListener;
public DatePickerDialog.OnDateSetListener setListener;
View view;
public UserFragment() {
}
public static UserFragment newInstance() {
UserFragment fragment = new UserFragment();
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
view = inflater.inflate(R.layout.adduser_fragment, container, false);
et_Date = (EditText) view.findViewById(R.id.etdate);
final FragmentManager fm = ((AppCompatActivity)getActivity()).getSupportFragmentManager();
et_Date.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
AppCompatDialogFragment newFragment = new DatePickerFragment();
newFragment.setTargetFragment(UserFragment.this,REQUEST_CODE);
newFragment.show(fm, "DatePicker");
}
});
return view;
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if(requestCode == REQUEST_CODE && resultCode == Activity.RESULT_OK){
selectedDate = data.getStringExtra("SelectedDate");
et_Date.setText(selectedDate);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if(context instanceof OnFragmentInteractionListener){
mListener= (OnFragmentInteractionListener) context;
}else{
throw new RuntimeException(context.toString()+"must implement OnFragmentInterationListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public interface OnFragmentInteractionListener {
public void onFragmentInteraction(Uri uri);
}
}

Your editText with id etdate is actually in layout adduser_fragment? This error may be because of view is in another layout(and you forgot that). Sorry for answer, I don't have enough reputation to post comment.

How to Access Activity(except mainactivity) from Fragment?

I created my test project where i code to communicate between two fragments but actully I want to access activity from fragment.
Here is code to connect fragment to fragment, its working absolutely right without any error but now i want to change this code to connect activity from fragment instead of fragment to fragment communication.
So Please change this code to access activities from fragment. I stuck on this issue for than a week.So Guys please resolve this.
here is my mainaactivity:
public class MainActivity extends AppCompatActivity implements FragmentA.FragmentAListener, FragmentB.FragmentBListener {
private FragmentA fragmentA;
private FragmentB fragmentB;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentA = new FragmentA();
fragmentB = new FragmentB();
getSupportFragmentManager().beginTransaction()
.replace(R.id.container_a, fragmentA)
.replace(R.id.container_b, fragmentB)
.commit();
}
#Override
public void onInputASent(CharSequence input) {
fragmentB.updateEditText(input);
}
#Override
public void onInputBSent(CharSequence input) {
fragmentA.updateEditText(input);
}
Here is my FragmentA.java:
public class FragmentA extends Fragment {
private FragmentAListener listener;
private EditText editText;
private Button buttonOk;
public interface FragmentAListener {
void onInputASent(CharSequence input);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_a, container, false);
editText = v.findViewById(R.id.edit_text);
buttonOk = v.findViewById(R.id.button_ok);
buttonOk.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
CharSequence input = editText.getText();
listener.onInputASent(input);
}
});
return v;
}
public void updateEditText(CharSequence newText) {
editText.setText(newText);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof FragmentAListener) {
listener = (FragmentAListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement FragmentAListener");
}
}
#Override
public void onDetach() {
super.onDetach();
listener = null;
}
}
Here is my FragmentB.java:
public class FragmentB extends Fragment {
private FragmentBListener listener;
private EditText editText;
private Button buttonOk;
public interface FragmentBListener {
void onInputBSent(CharSequence input);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_b, container, false);
editText = v.findViewById(R.id.edit_text);
buttonOk = v.findViewById(R.id.button_ok);
buttonOk.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
CharSequence input = editText.getText();
listener.onInputBSent(input);
}
});
return v;
}
public void updateEditText(CharSequence newText) {
editText.setText(newText);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof FragmentBListener) {
listener = (FragmentBListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement FragmentBListener");
}
}
#Override
public void onDetach() {
super.onDetach();
listener = null;
}
}
Here is my Fertilizers.java file which i want to access from FragmentA.:
public class Fertilizers extends AppCompatActivity {
RecyclerView mRecyclerView;
List<FertilizerData> myFertilizersList;
FertilizerData mFertilizersData;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fertilizers);
mRecyclerView = (RecyclerView)findViewById(R.id.recyclerView);
GridLayoutManager gridLayoutManager;
gridLayoutManager = new GridLayoutManager(Fertilizers.this, 1);
mRecyclerView.setLayoutManager(gridLayoutManager);
myFertilizersList = new ArrayList<>();
mFertilizersData = new FertilizerData("Urea Fertilizer","Urea is a concent","Rs.1900",R.drawable.urea);
myFertilizersList.add(mFertilizersData);
myFertilizersList.add(mFertilizersData); }
}
please write here a block of code to call Fertilzers Activity from FragmentA, I,ll be very thankful to you.

Calling getActivity() in your fragment gives you the calling activity so if MainActivity started your fragment then you would do
(MainActivity(getActivity())).something_from_your_main_activity

Solution found by itself regarding this issue.
FragmentHome.java class should look like this:
public class FragmentHome extends Fragment {
private Button button;
public FragmentHome(){
}
public interface OnMessageReadListener
{
public void onMessageRead(String message);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_home, container, false);
button = (Button)v.findViewById(R.id.bn);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(getActivity(), Fertilizers.class);
intent.putExtra("some"," some data");
startActivity(intent);
}
});
return v;
}
}
FertilizersActivity.java should look like this:
public class Fertilizers extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fertilizers);
Bundle bundle = getIntent().getExtras();
if (bundle != null){
if(bundle.getStringArrayList("some") !=null){
Toast.makeText(getApplicationContext(),"data:" + bundle.getStringArrayList("some"),Toast.LENGTH_LONG).show();
}
}
}
}

Sending a variable from a fragment to MainActivity

In my app I have three fragments. In the third fragment, a variable is take from a seekBar. Now I want to use this variable in my MainActivity. I tried to send the variable with an intent and show it in a textView onClick to test it, but the textView only shows „null“. Why isn‘t the variable send to the activity?
My MainActivity:
public class MainActivity extends AppCompatActivity {
TextView textTest;
public int a = 33;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textTest = (TextView) findViewById(R.id.textView3);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent intent = getIntent();
String messages = intent.getStringExtra("message");
textTest.setText(String.valueOf(messages));
}
});
}
}
My Fragment that sends the variable:
public class ItemThreeFragment extends Fragment {
SeekBar seekBar;
TextView textView11;
int value = 10;
public static ItemThreeFragment newInstance() {
ItemThreeFragment fragment = new ItemThreeFragment();
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_item_three, container, false);
seekBar = (SeekBar) view.findViewById(R.id.seekBar);
seekBar.setMax(25);
seekBar.setProgress(value);
textView11 = (TextView) view.findViewById(R.id.textView11);
textView11.setText("" + value);
seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
#Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
value = i;
textView11.setText("" + value);
Intent intent = new Intent(getActivity().getBaseContext(),
MainActivity.class);
intent.putExtra("message", value);
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
})
return view;
}
}

The problems are
In your activity, Intent intent = getIntent(); will get the intent that starts MainActivity.
In your fragment's onProgressChanged, your code doesn't communicate with MainActivity at all.
I can think of two relatively simple solutions for now:
Call a MainActivity function using ((MainActivity) getActivity()).someFunction() in your fragment.
In the MainActivity, use ((YourFragment) getSupportFragmentManager().findFragmentById(R.id.your_fragment_id)).property to access the fragment object's content. You can put the seek bar value into a class variable.
And check this: Communicating between a fragment and an activity - best practices

getActivity().findViewById(R.id.textView3).setText(""+value);
put the code inside onProgressChanged(),I hope its help you.

I think you missed startActivity(intent).
Intent intent = new Intent(getActivity().getBaseContext(),
MainActivity.class);
intent.putExtra("message", value);
getActivity().startActivity(intent);

Android, how to update ListView content from external activity?

I have a project with 4 classes: 2 activities, 1 adapter and 1 class for simple object. Names of the classes are: MainActivity, AddingItemsActivity, ItemAdapter, SimpleItem. In a layout corresponding to the MainActivity, there is a list view named SimpleListView. SimpleListView should contain SimpleItem objects. ItemAdapter is made to handle SimpleListView. Updating, adding items to SimpleListView from MainActivity is very easy. What I would like to reach is updating, adding items, which appear on the SimpleListView, from AddingItemsActivity (appear when user come back to the MainActivity). Could you tell me what should I do to reach that?
PS: I would like to ask: "how to update SimpleListView from AddingItemsActivity?" but I have read that it is not proper question, beacuse SimpleListView does not exist in AddingItemsActivity.
MainActivity
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button toAddingActivity = findViewById(R.id.toAddingActivitybutton);
final ListView simpleItemsListView = findViewById(R.id.SimpleListView);
final ItemAdapter mAdapter = new ItemAdapter(this, R.layout.simple_item_adapter);
toAddingActivity.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(getBaseContext(), AddingItemsActivity.class);
startActivity(intent);
}
});
}
}
AddingItemsActivity
public class AddingItemsActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_adding_items);
Button addItem = findViewById(R.id.AddItembutton);
// final ListView simpleItemsListView = findViewById(R.id.SimpleListView);
// final ItemAdapter mAdapter = new ItemAdapter(this, R.layout.simple_item_adapter);
addItem.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// first reflex try, which does not work:
// SimpleItem item = new SimpleItem("String number 1", "String number 2");
// mAdapter.add(item);
// simpleItemsListView.setAdapter(mAdapter);
}
});
}
}
ItemAdapter
public class ItemAdapter extends ArrayAdapter<SimpleItem>{
public ItemAdapter(Context context, int textViewResourceId) {
super(context, textViewResourceId);
}
public ItemAdapter(Context context, int resource, List<SimpleItem> items) {
super(context, resource, items);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi;
vi = LayoutInflater.from(getContext());
v = vi.inflate(R.layout.simple_item_adapter, null);
}
SimpleItem item = getItem(position);
if (item != null) {
TextView tv1 = v.findViewById(R.id.adapterTextView1);
TextView tv2 = v.findViewById(R.id.adapterTextView2);
tv1.setText(item.getStr1());
tv2.setText(item.getStr2());
}
return v;
}
}
SimpleItem
public class SimpleItem {
private String str1;
private String str2;
public SimpleItem(String s1, String s2)
{
str1 = s1;
str2 = s2;
}
public String getStr1()
{
return str1;
}
public String getStr2()
{
return str2;
}
}

Use startActivityForResult to get the result as SimpleItem from AddingItemsActivity.
Intent intent = new Intent(getBaseContext(), AddingItemsActivity.class);
startActivityForResult(intent,1);
Create a SimpleItem in AddingItemsActivity, add values to it and use setResult to give simple item instance back to MainActivity
// inside on click
SimpleItem item = new SimpleItem("String number 1", "String number 2");
Intent returnIntent = new Intent();
returnIntent.putExtra("result", item);
setResult(Activity.RESULT_OK,returnIntent);
finish();`
In MainActivity
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 1) {
if(resultCode == Activity.RESULT_OK){
SimpleItem result = (SimpleItem)data.getSerializableExtra("result");
// add result to the list, used by adapter
// notify adapter using notifyDataSetChanged
}
}
}//onActivityResult
Note : add public class SimpleItem implements Serializable and seems like you forgot to create and pass list to adapter instances, so simply create it

your adaper is not complete you must override getCount method and set your list.size() to it . then from your MainActivity you mast create a list of simle item and pass it to your adapter .
ArrayList<SimpleItem> items=new ArrayList<>();
final ItemAdapter mAdapter = new ItemAdapter(this, R.layout.simple_item_adapter,items);
then you can put your list to intent and pass it to AddingItemsActivity .
Intent intent=new Intent (this,AddingItemsActivity.class);
intent.putExtra("Key",items);
startActivityForResult(intent,your request code (exam : 14));
and in AddingItemsActivity :
Bundle bundel=getIntent().getExtras();
ArrayList<SimpleItem> items=(ArrayList<SimpleItem>)bundle.get("Key");
change or add items to list and return it to MainActivity :
Intent returnIntent = new Intent();
returnIntent.putExtra("returnedList", item);
setResult(Activity.RESULT_OK,returnIntent);
finish();
and in onActivityResult of MainActivity :
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 14) {
if(resultCode == Activity.RESULT_OK){
// ArrayList<SimpleItem> items=(ArrayList<SimpleItem>)data.getSerializableExtra("returnedList");
items=(ArrayList<SimpleItem>)data.getSerializableExtra("returnedList");
mAdapter .notifyDataSetChanged();
}
}
}
And dont forgot implemens your simpleItem class of Serializable

try this :
MainActivity :
public class MainActivity extends AppCompatActivity {
private ArrayList<SimpleItem> items = new ArrayList<>();
private Button toAddingActivity;
private ListView simpleItemsListView;
private ItemAdapter mAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toAddingActivity = (Button) findViewById(R.id.toAddingActivitybutton);
simpleItemsListView = (ListView) findViewById(R.id.SimpleListView);
mAdapter = new ItemAdapter(this, R.layout.simple_item_adapter, items);
simpleItemsListView.setAdapter(mAdapter);
toAddingActivity.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, AddingItemsActivity.class);
startActivityForResult(intent, 14);
}
});
mAdapter.notifyDataSetChanged();
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 14 && resultCode == Activity.RESULT_OK) {
Bundle bundle = data.getExtras();
SimpleItem item=(SimpleItem) bundle.get("reKey");
items.add(item);
mAdapter.notifyDataSetChanged();
}
}
}
ItemAdapter :
public class ItemAdapter extends ArrayAdapter<SimpleItem>{
private ArrayList<SimpleItem> items =new ArrayList<>();
private Activity activity;
private int layoutResource;
public ItemAdapter(#NonNull Activity act, int resource, #NonNull ArrayList<SimpleItem> data) {
super(act, resource, data);
items =data;
activity=act;
layoutResource=resource;
}
#Override
public int getCount() {
return items.size();
}
#Override
public SimpleItem getItem(int position) {
return items.get(position);
}
#Override
public View getView(int position, #Nullable View convertView, #NonNull ViewGroup parent) {
ViewHolder holder;
View row=convertView;
if(row==null || (row.getTag()==null)){
LayoutInflater inflater=LayoutInflater.from(activity);
row=inflater.inflate(layoutResource,null);
holder=new ViewHolder();
holder.tv1=row.findViewById(R.id.adapterTextView1);
holder.tv2=row.findViewById(R.id.adapterTextView2);
row.setTag(holder);
}else {
holder=(ViewHolder)row.getTag();
}
holder.simpleItem=items.get(position);
holder.tv1.setText(holder.simpleItem.getStr1());
holder.tv2.setText(holder.simpleItem.getStr2());
return row;
}
class ViewHolder{
TextView tv1;
TextView tv2;
SimpleItem simpleItem;
}
}
AddingItemsActivity :
public class AddingItemsActivity extends AppCompatActivity{
private Button addItem;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_adding_items);
addItem=(Button)findViewById(R.id.AddItembutton);
addItem.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
SimpleItem item = new SimpleItem("String number 1", "String number 2");
Intent returnIntent = new Intent();
returnIntent.putExtra("reKey",item);
setResult(Activity.RESULT_OK,returnIntent);
finish();
}
});
}
}
you can change AddingItemsActivity onclick method

Handling Multiple Fragments when orientation changes

I have a MainActivity, and I want to attach a fragment with 3 buttons in it to that activity. On clicking button 1 it should replace this fragment with another fragment. But when I change orientation the current fragment and the old fragment are both getting attached. Can someone help me solve this ?
Following is my MainActivity.java:
public class MainActivity extends AppCompatActivity implements OnButtonsClickListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getSupportFragmentManager().beginTransaction()
.add(R.id.mainactivity, new FragmentHomepage(), "aboutMe")
.commit();
}
#Override
public void button1Action() {
FragmentAboutMe fragmentAboutMe=new FragmentAboutMe();
getSupportFragmentManager().beginTransaction()
.add(R.id.mainactivity,fragmentAboutMe)
.commit();
}
#Override
public void button2Action() {
Intent intent =new Intent(this,ActivityMasterDetail.class);
startActivity(intent);
}
#Override
public void button3Action() {
Intent intent =new Intent(this,ActivityViewPager.class);
startActivity(intent);
}
}
This is my FragmentHomepage.java:
public class FragmentHomepage extends Fragment {
private static final String ARG_SECTION_NUMBER ="section number";
OnButtonsClickListener onButtonsClickListener;
public static FragmentHomepage newInstance(int sectionNumber){
FragmentHomepage fragmentHomepage=new FragmentHomepage();
Bundle args=new Bundle();
args.putInt(ARG_SECTION_NUMBER,sectionNumber);
fragmentHomepage.setArguments(args);
return fragmentHomepage;
}
public FragmentHomepage(){}
#Override
public void onAttach(Context context) {
super.onAttach(context);
try {
onButtonsClickListener= (OnButtonsClickListener) context;
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
final Button button1= (Button) getActivity().findViewById(R.id.aboutMe);
final Button button2= (Button) getActivity().findViewById(R.id.task2);
final Button button3= (Button) getActivity().findViewById(R.id.task3);
button1.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
onButtonsClickListener.button1Action();
}
});
button2.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
onButtonsClickListener.button2Action();
}
});
button3.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
onButtonsClickListener.button3Action();
}
});
}
#Nullable
#Override
public View onCreateView(final LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
View rootView=null;
rootView =inflater.inflate(R.layout.fragment_homepage,container,false);
return rootView;
}
}
and my second activity is as follows
(in FragmentAboutMe.java):
public class FragmentAboutMe extends Fragment {
int counters=0;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(savedInstanceState==null)counters=0;
else counters=savedInstanceState.getInt("count");
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("count",13);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_aboutme,container,false);
}
}

In your onCreate() method put a check whether the fragment is already present. Android automatically restores the fragment manager state upon orientation change and hence upon orientation change, the fragment which you added on button click would automatically be added. Thus if you will add new fragment in onCreate() without check, this would result in adding the 2 fragments. This is causing the issue.
FragmentManager fm = getSupportFragmentManager();
if (fm.findfragmentById(R.id.mainactivity) == null) {
FragmentHomepage fragment = new FragmentHomepage ();
fm.beginTransaction().add (R.id.mainactivity, fragment).commit();
}

You would want to save the state. You would need to extend Fragment to store the objects that need saving.
Override the onConfigurationChanged(..) and it should work out.
When I had to handle screen orientation changes, I recall having used this reference [link].

There are two ways.
Either you need to save the state in the bundle in onSaveInstanceState() method. Also save the states of fragment.
When activity recreate itself then check the value of bundle inside onCreate() or onRestoreInstanceState() method. Now initialize all the objects as before.
Else
set the value of activity inside manifest file as
android:configChanges="layoutDirection|orientation|screenLayout|screenSize"
and override the method.
#Override
public void onConfigurationChanged(Configuration newConfig) {
}
Second technique will not allow the activity to restart on orientation change.