I've been looking at the android documentation and diverse sources around the web, but I can't seem to get my app to retain data across activity re-creation (like pressing the back button to exit and then entering the app from the icon or the task manager).
I have 3 classes: the main one (extends FragmentActivity), a fragment and a class that should run in the background while the app is not active, and after the activity is created, it needs to update the fragment.
Here are my sources:
Main
public class Main extends FragmentActivity {
private FragmentExample mFragment;
private BackgroundClass bgClass = new BackgroundClass();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
manageFragment(getSupportFragmentManager());
}
protected void manageFragment(FragmentManager fm) {
mFragment = (FragmentExample) fm.findFragmentByTag("TAG");
if (mFragment == null) {
mFragment = new mFragment();
fm.beginTransaction().add(mFragment,"TAG").commit();
}
else fm.beginTransaction().attach(mFragment).commit();
}
#Override
protected void onStart() {
super.onStart();
mFragment = bgClass.update(mFragment);
}
}
Fragment
public class FragmentExample extends Fragment {
//declare variables
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment, container, false);
//initialize variables from View
return view;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
//more initializations
}
}
BackgroundClass
public class BackgroundClass extends SomeOtherClass {
//declare variables
protected FragmentExample update(final FragmentExample fExample) {
//update listeners, variables, etc
return fExample;
}
//Overridden methods from SomeOtherClass
}
Currently it updates the data only when I change the configuration (i.e. rotating the screen). Any sort of help would be great.
Related
I'm trying to execute AsyncTask from a fragment class (e.g MyFragment.java) from another Activity class (e.g MyActivity.java).
the fragment class MyFragment.java is updating UI on it's elements :
public class MyFragment extends Fragment {
private SwipeRefreshLayout myRefreshLayout;
private ArrayAdapter myListAdapter;
#Override
public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); }
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
myListAdapter = new myCustomAdapter(getContext(), myDataArray);
myRefreshLayout = myView.findViewById(R.id.myRefreshLayout);
}
public class MyTask extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// UI...
myRefreshLayout.setRefreshing(true);
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// UI...
myRefreshLayout.setRefreshing(false);
myListAdapter.notifyDataSetChanged();
}
#Override
protected Void doInBackground(Void... params) {
// code...
return null;
}
}
}
I'm trying to Execute AsyncTask from MyActivity.java
MyFragment myfragment = new MyFragment();
myfragment.new MyTask.execute();
The Application crashes at onPreExecute :
java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.swiperefreshlayout.widget.SwipeRefreshLayout.setRefreshing(boolean)' on a null object reference.
I'm assuming this is because it couldn't access myRefreshLayout to perform setRefreshing(true) on it, because i'm running the task from another thread MyActivity.java
How can i execute the AsyncTask on the Fragment .. from the Activity and change the UI?
Thanks.
Idk if this would be a nice solution. But I think you can make MainActivity implements this custom interface. It'd be a callback that should be execute after the swipe action done.
public class MainActivity extends AppCompatActivity implements MyAsyncCallback {
....
....
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MyFragment myfragment = new MyFragment();
myfragment.new MyTask(this).execute();
}
#Override
public void onPreExecute(Boolean isRefreshing) {
if(isRefreshing){
// UPDATE MAIN UI
}
}
#Override
public void onPostExecute(Boolean isRefreshing) {
if(isRefreshing){
// UPDATE MAIN UI
}
}
}
interface MyAsyncCallback {
void onPreExecute(Boolean isRefreshing);
void onPostExecute(Boolean isRefreshing);
}
in your fragment
public class MyTask extends AsyncTask<Void, Void, Void> {
WeakReference<MyAsyncCallback> myListener;
public MyTask(MyAsyncCallback listener){
this.myListener = listener
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// don't forget to return view
}
#Override
protected void onPreExecute() {
super.onPreExecute();
MyAsyncCallback myListener = this.myListener.get();
if (myListener != null) {
myListener.onPreExecute(true);
}
myRefreshLayout.setRefreshing(true);
}
//same for onPostExecute()
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();
}
}
}
}
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.
I want to have a function that is constant between all my Fragments placed in MainActivity. I am not sure how to pass the data to the active Fragment since the Fragment will be unaware of the function being run.
I have tried creating an interface in the MainActivity and have the Fragment implement the MainActivity.OnDataPass. but not sure how to initiate the interface in the MainActivity I keep getting a NullPointerException.
In my main activity:
public class Mainactivity extends FragmentActivity{
OnDataPass dataPasser;
BroadcastReceiver receiver;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
receiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String str = intent.getStringExtra("data");
dataPasser.onDataPass(str);
}
};
}
public interface OnDataPass {
public void onDataPass(String data);
}
}
In my Fragment
public class Storage extends Fragment implements Mainactivity.OnDataPass{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
mrootview = (ViewGroup) inflater.inflate(R.layout.storage, container, false);
return mrootview;
}
#Override
public void onDataPass(String data) {
Log.v(TAG, data);
}
}
am I even on the right track or is there a better way to send data to the fragment?
You are pretty far already:
public class Mainactivity extends FragmentActivity{
OnDataPass dataPasser;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//When you create your fragment, keep a reference of it in the dataPasser variable
dataPasser = /* your storage fragment class or any other fragment that implements onDataPass*/
......
receiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String str = intent.getStringExtra("data");
dataPasser.onDataPass(str);
}
};
}
public interface OnDataPass {
public void onDataPass(String data);
}
}
I'm developing an Android app and am to the point where I would like to integrate Facebook login onto the main page. I am following these directions for the same:
https://developers.facebook.com/docs/android/login-with-facebook/#step1
Part of the walkthrough lists changing the MainActivity class to extend FragmentActivity. My MainActivity class, however, already extended it because of a content slider I implemented on the main view. The original onCreate code of MainActivity was:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Instantiate a ViewPager and a PagerAdapter.
mPager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new ScreenSlidePagerAdapter(getFragmentManager());
mPager.setAdapter(mPagerAdapter);
mPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
invalidateOptionsMenu();
}
});
}
And this was working great. Following the Facebook login walkthrough, I added a new 'MainFragment' class following the directions as literally as possible:
public class MainFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.main, container, false);
return view;
}
}
, also added a com.facebook.widget.LoginButton to my MainActivity layout (this seems to display fine), and tried to tie it all together by adding the following to the OnCreate section of the MainActivity class (displayed above, but not repeating it all here again for brevity):
if (savedInstanceState == null) {
// Add the fragment on initial activity setup
mainFragment = new MainFragment();
getSupportFragmentManager()
.beginTransaction()
.add(android.R.id.content, mainFragment)
.commit();
} else {
// Or set the fragment from restored state info
mainFragment = (MainFragment) getSupportFragmentManager()
.findFragmentById(android.R.id.content);
}
The question I fundamentally have is how to make both my existing slider and Facebook login play together nicely? If I add the Facebook code needed to OnCreate of MainActivity, then my slider goes away. If I don't add the code, then Facebook login obviously doesn't work. I've read as much as possible on Fragments thinking I might be doing something wrong there, but haven't had much luck...
Thanks in advance for any help you can provide!
Here is my solution, you make your MainActivity as the first level, in this level your Android app will check whether the user is logged or not, based on this, go to the second level, which is either a Facebook login page or the content slider. For implementation, it would be like this:
This is the MainActivity:
public class MainActivity extends FragmentActivity{
private LoginFragment loginFragment;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
// Add the fragment on initial activity setup
loginFragment = new LoginFragment();
getSupportFragmentManager()
.beginTransaction()
.add(android.R.id.content, loginFragment)
.commit();
} else {
// Or set the fragment from restored state info
loginFragment = (LoginFragment) getSupportFragmentManager()
.findFragmentById(android.R.id.content);
}
}
}
This is the LoginFragment:
public class LoginFragment extends Fragment {
private LoginButton authButton;
private static final String TAG = "MainFragment";
private UiLifecycleHelper uiHelper;
private Session.StatusCallback callback = new Session.StatusCallback() {
#Override
public void call(Session session, SessionState state, Exception exception) {
onSessionStateChange(session, state, exception);
}
};
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.login_fragment,
container, false);
authButton=(LoginButton)view.findViewById(R.id.login_button);
authButton.setFragment(this);
return view;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
uiHelper = new UiLifecycleHelper(getActivity(), callback);
uiHelper.onCreate(savedInstanceState);
}
#Override
public void onResume() {
super.onResume();
Session session = Session.getActiveSession();
if (session != null &&
(session.isOpened() || session.isClosed()) ) {
onSessionStateChange(session, session.getState(), null);
}
uiHelper.onResume();
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
uiHelper.onActivityResult(requestCode, resultCode, data);
}
#Override
public void onPause() {
super.onPause();
uiHelper.onPause();
}
#Override
public void onDestroy() {
super.onDestroy();
uiHelper.onDestroy();
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
uiHelper.onSaveInstanceState(outState);
}
private void onSessionStateChange(Session session, SessionState state, Exception exception) {
if (state.isOpened()) {
Log.i(TAG, "Logged in...");
startActivity(new Intent(getActivity(), ContentSliderActivity.class));
} else if (state.isClosed()) {
Log.i(TAG, "Logged out...");
}
}
}
And here is the activity which you suppose to have a content slider, this will be displayed after the user has successfully logged in, here I call it ContentSliderActivity:
public class ContentSliderActivity extends FragmentActivity{
.....................
}
I was able to discern the problem was in the MainFragment on CreateView method. For some reason, if I removed this override, I didn't have a problem where my content sliderr gets removed. No idea why, but instead of adding the following lines: LoginButton authButton = (LoginButton) findViewById(R.id.authButton); authButton.setFragment(this); in the onViewCreate method of MainFragment, I simply moved them to the onCreate method in MainActivity. Seems to have worked for me, although not entirely sure what the original problem was honestly.