Develop Reference

How to provide listeners for different fragment in a viewpager from a button in activity

I am trying to create a form using fragments in a viewpager which is a step by step process.
there are 6 fragments in the viewpager. a "Back" button and a "Next" button(in the activity).
I want to save the form when the user clicks the "Next" button.
To the Reference here is the code
The Adapter to load the Fragments
public class RegistrationPagerAdapter extends FragmentPagerAdapter {
Fragment fragment;
public RegistrationPagerAdapter(#NonNull FragmentManager fm, int behavior) {
super(fm, behavior);
}
#NonNull
#Override
public Fragment getItem(int position) {
switch (position){
case 0:
fragment = new PersonalDetailsFragment();
break;
case 1:
fragment = new AboutMeFragment();
break;
case 2:
fragment = new HoroscopeFragment();
break;
case 3:
fragment = new EducationFragment();
break;
case 4:
fragment = new FamilyFragment();
break;
case 5:
fragment = new ExpectationFragment();
break;
}
return fragment;
}
#Override
public int getCount() {
return 6;
}
#Override
public int getItemPosition(#NonNull Object object) {
return POSITION_NONE;
}
}
There are two buttons in the activity(not in fragments)
public class FormActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = "FormActivity";
AppCompatButton backButton, nextButton;
CustomViewPager viewpager;
Toolbar toolbar;
ApiInterface apiInterface;
RegistrationPagerAdapter adapter;
int status;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_form);
initilizeToolbar();
}
#Override
protected void onRestart() {
super.onRestart();
}
private void initilizeToolbar() {
apiInterface = ApiClient.getClient(getApplicationContext()).create(ApiInterface.class);
toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
if (getSupportActionBar() != null) {
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
castComponents();
}
private void castComponents() {
viewpager = findViewById(R.id.viewPager);
backButton = findViewById(R.id.backButton);
nextButton = findViewById(R.id.nextButton);
nextButton.setOnClickListener(this);
backButton.setOnClickListener(this);
GetAllDetailsOfUser();
}
#Override
public void onResume() {
initilizeToolbar();
super.onResume();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
return super.onCreateOptionsMenu(menu);
}
public void setViewPagerData(int status) {
FragmentManager fm = getSupportFragmentManager();
adapter = new RegistrationPagerAdapter(fm, 0);
viewpager.setAdapter(adapter);
viewpager.setCurrentItem(status);
viewpager.setPagingEnabled(false);
}
public void GetAllDetailsOfUser() {
Call<AllProfileDetails> allDetails = apiInterface.allDetails(PrefUtils.getToken(this), PrefUtils.getID(this));
allDetails.enqueue(new Callback<AllProfileDetails>() {
#Override
public void onResponse(Call<AllProfileDetails> call, Response<AllProfileDetails> response) {
AllProfileDetails all = response.body();
if (all != null) {
if (all.getStatus()) {
Data data = all.getData();
setViewPagerData(data.getProfileCurrentStatus());
status = data.getProfileCurrentStatus();
}
}
}
public void onFailure(Call<AllProfileDetails> call, Throwable t) {
Crashlytics.log(t.getLocalizedMessage());
}
});
}
#Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.backButton:
if (viewpager.getCurrentItem() == 0){
}else{
viewpager.setCurrentItem(viewpager.getCurrentItem() - 1);
}
break;
case R.id.nextButton:
if (viewpager.getCurrentItem() == 6){
}else{
viewpager.setCurrentItem(viewpager.getCurrentItem() + 1);
}
break;
}
}
}
this is Code is Fine but here is the problem...
When i save the data in Fragment1 i.e "PersonalDetailsFragment", it moves to fragment2 i.e "AboutMeFragment"
again when i click on save button for "AboutMeFragment" it runs the method of "PersonalDetailsFragment" only
please note that i call the activity buttons in fragments as
getActivity().findViewById(R.id.backButton);
getActivity().findViewById(R.id.nextButton);

You should have a interface like OnSaveTapped.
public interface OnSaveTapped{
void onSaveTapped();
}
Then make the fragments implement the interface above, ex:
public class PersonalDetailsFragment extends Fragment implements OnSaveTapped{
public void onSaveTapped(){
//do your business code here to save data
}
}
Finally ,In the activity class:
#Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.backButton:
if (viewpager.getCurrentItem() == 0){
}else{
viewpager.setCurrentItem(viewpager.getCurrentItem() - 1);
}
break;
case R.id.nextButton:
if (viewpager.getCurrentItem() == 6){
}else{
viewpager.setCurrentItem(viewpager.getCurrentItem() + 1);
}
break;
case R.id.button_save:
((OnSaveTapped)viewpager.getCurrentFragment()).onSaveTapped();
}
Don't forget to create new method named getCurrentFragment() to return current item (fragment) in RegistrationPagerAdapter.
public class RegistrationPagerAdapter extends FragmentPagerAdapter {
private Fragment fragment;
/**other lines of code*/
public Fragment getCurrentFragment(){
return fragment;
}
}

How to restore fragment states while using bottom navigation view in android?

I am trying to do restoring the fragment view state values(text view,..etc) when back from second fragment in android bottom navigation view.
MyActivity.java
public class LandingPage extends AppCompatActivity implements ProductFragment.AddToCart {
Fragment fragment;
TextView txtCart;
Button btnCart;
ItemData itemData;
ArrayList<ItemData> itemDataList;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.nav_home:
fragment = new ProductFragment();
loadFragment(fragment);
return true;
case R.id.nav_profile:
fragment = new ReportsFragment();
loadFragment(fragment);
return true;
case R.id.nav_logout:
LogOut();
return true;
}
return true;
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_landing_page);
txtCart = findViewById(R.id.txt_cart);
btnCart = findViewById(R.id.btn_cartImg);
itemDataList = new ArrayList<>();
BottomNavigationView bottomNavigationView = findViewById(R.id.navigation);
bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
loadFragment(new ProductFragment());
}
private void loadFragment(Fragment fragment) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.fragment_container, fragment);
transaction.commit();
}
}
ProductFragment.java
public class ProductFragment extends Fragment {
private OnFragmentInteractionListener mListener;
Button btnCart1,btnCart2,btnCart3;
AddToCart addToCart;
TextView txtItem1Des,txtItem1Price,txtItem2Des,txtItem2Price,txtItem3Des,txtItem3Price;
Button btnCart1Inc,btnCart1Dec,btnCart2Inc,btnCart2Dec,btnCart3Inc,btnCart3Dec;
TextView cart1txt,cart2txt,cart3txt;
String itemDes,itemPrice,itemImg,itemCount;
int quantity1,quantity2,quantity3;
public ProductFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_product, container, false);
btnCart1 = view.findViewById(R.id.cart1);
txtItem1Des = view.findViewById(R.id.cart1_desc);
txtItem1Price = view.findViewById(R.id.cart1_price);
btnCart1Inc = view.findViewById(R.id.cart1Inc);
btnCart1Dec = view.findViewById(R.id.cart1Dec);
cart1txt = view.findViewById(R.id.cart1txt);
btnCart2 = view.findViewById(R.id.cart2);
txtItem2Des = view.findViewById(R.id.cart2_desc);
txtItem2Price = view.findViewById(R.id.cart2_price);
btnCart2Inc = view.findViewById(R.id.cart2Inc);
btnCart2Dec = view.findViewById(R.id.cart2Dec);
cart2txt = view.findViewById(R.id.cart2txt);
btnCart3 = view.findViewById(R.id.cart3);
txtItem3Des = view.findViewById(R.id.cart3_desc);
txtItem3Price = view.findViewById(R.id.cart3_price);
btnCart3Inc = view.findViewById(R.id.cart3Inc);
btnCart3Dec = view.findViewById(R.id.cart3Dec);
cart3txt = view.findViewById(R.id.cart3txt);
quantity1 = Integer.parseInt(cart1txt.getText().toString());
quantity2 = Integer.parseInt(cart2txt.getText().toString());
quantity3 = Integer.parseInt(cart3txt.getText().toString());
buttonInitialization();
addingToCart();
return view;
}
private void addingToCart() {
btnCart1Dec.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(quantity1 <= 1){
btnCart1.setVisibility(View.VISIBLE);
btnCart1Dec.setVisibility(View.INVISIBLE);
btnCart1Inc.setVisibility(View.INVISIBLE);
cart1txt.setVisibility(View.INVISIBLE);
addToCart.removeItemFromCart(1);
}else {
quantity1 = quantity1-1;
cart1txt.setText(String.valueOf(quantity1));
addToCart.itemCount(cart1txt.getText().toString(),"1");
}
}
});
btnCart1Inc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
quantity1 = quantity1+1;
cart1txt.setText(String.valueOf(quantity1));
addToCart.itemCount(cart1txt.getText().toString(),"1");
}
});
btnCart2Dec.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(quantity2 <= 1){
btnCart2.setVisibility(View.VISIBLE);
btnCart2Dec.setVisibility(View.INVISIBLE);
btnCart2Inc.setVisibility(View.INVISIBLE);
cart2txt.setVisibility(View.INVISIBLE);
addToCart.removeItemFromCart(2);
}else {
quantity2 = quantity2-1;
cart2txt.setText(String.valueOf(quantity2));
addToCart.itemCount(cart2txt.getText().toString(),"2");
}
}
});
btnCart2Inc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
quantity2 = quantity2+1;
cart2txt.setText(String.valueOf(quantity2));
addToCart.itemCount(cart2txt.getText().toString(),"2");
}
});
btnCart3Dec.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(quantity3 <= 1){
btnCart3.setVisibility(View.VISIBLE);
btnCart3Dec.setVisibility(View.INVISIBLE);
btnCart3Inc.setVisibility(View.INVISIBLE);
cart3txt.setVisibility(View.INVISIBLE);
addToCart.removeItemFromCart(3);
}else {
quantity3 = quantity3-1;
cart3txt.setText(String.valueOf(quantity3));
addToCart.itemCount(cart3txt.getText().toString(),"3");
}
}
});
btnCart3Inc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
quantity3 = quantity3+1;
cart3txt.setText(String.valueOf(quantity3));
addToCart.itemCount(cart3txt.getText().toString(),"3");
}
});
}
private void buttonInitialization() {
btnCart1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
itemImg = "";
itemPrice = txtItem1Price.getText().toString().trim();
itemDes = txtItem1Des.getText().toString().trim();
itemCount = cart1txt.getText().toString().trim();
addToCart.cartCount("",itemPrice,itemDes,itemCount,"1");
btnCart1.setVisibility(View.INVISIBLE);
btnCart1Dec.setVisibility(View.VISIBLE);
btnCart1Inc.setVisibility(View.VISIBLE);
cart1txt.setVisibility(View.VISIBLE);
}
});
btnCart2.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
itemImg = "";
itemPrice = txtItem2Price.getText().toString().trim();
itemDes = txtItem2Des.getText().toString().trim();
itemCount = cart2txt.getText().toString().trim();
addToCart.cartCount("",itemPrice,itemDes,itemCount,"2");
btnCart2.setVisibility(View.INVISIBLE);
btnCart2Dec.setVisibility(View.VISIBLE);
btnCart2Inc.setVisibility(View.VISIBLE);
cart2txt.setVisibility(View.VISIBLE);
}
});
btnCart3.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
itemImg = "";
itemPrice = txtItem3Price.getText().toString().trim();
itemDes = txtItem3Des.getText().toString().trim();
itemCount = cart3txt.getText().toString().trim();
addToCart.cartCount("",itemPrice,itemDes,itemCount,"3");
btnCart3.setVisibility(View.INVISIBLE);
btnCart3Dec.setVisibility(View.VISIBLE);
btnCart3Inc.setVisibility(View.VISIBLE);
cart3txt.setVisibility(View.VISIBLE);
}
});
}
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
addToCart = (AddToCart) context;
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public interface OnFragmentInteractionListener {
void onFragmentInteraction(Uri uri);
}
public interface AddToCart{
void cartCount(String item_img,String item_price,String item_desc,String item_count,String item_pos);
void removeItemFromCart(int removeItem);
void itemCount(String itemCount,String position);
}
}
Here in ProductFragment iam going to add values to text view. When i was coming from ReportFragment the view values are going to be cleared in ProductFragment.

I would consider doing that in two steps:
save fragment instance instead of re-creating a new one every time
private ProductFragment productFragment;
private ReportsFragment reportsFragment;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.nav_home:
if(productFragment == null)
productFragment = new ProductFragment();
loadFragment(productFragment);
break;
case R.id.nav_profile:
if(reportsFragment == null)
reportsFragment = new ReportsFragment();
loadFragment(reportsFragment);
break;
case R.id.nav_logout:
LogOut();
return true;
}
return true;
}
};
referring to this question/answer, you should implement in your fragment both void onSaveInstanceState(final Bundle outState) and void onActivityCreated(Bundle savedInstanceState)
In that way you will surely keep the instance of your fragment instead of creating a new one every time (new MyFragment() will always re-create it). In addition, saving your views state in onSaveInstanceState and restoring it in your onActivityCreate, will allow you to keep your views/values.
I wrote that by hand without a compiler, so it might not be perfect.
let me know if you need further information.
Good luck

I am using this solution and it works for me.

You should see my detailed answer to a similar question. I hope it will solve your problem.

RecyclerView.Adapter is null in ViewPager Fragment

public class MainLibraryFragment extends Fragment implements PlaylistChangedInterface {
AudioItemSelectedListener mCallback;
// Container Activity must implement this interface
public interface AudioItemSelectedListener {
// public void onAudioItemSelected(int position);
public void onAudioItemSelected(Audio audioSelected);
}
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private Context context;
private ArrayList<Audio> listToDisplay;
private String TAG = "MainLibraryFragment";
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
context = getActivity();
MemoryManagement memoryManagement = new MemoryManagement(context);
listToDisplay = memoryManagement.loadAudioList(MemoryManagement.MAIN_LIST_KEY);
try {
//Expression is meaningless but tests if null.
//TODO, should catch this in loadAudioList.
if (listToDisplay.isEmpty()){}
} catch (NullPointerException e){
defaultList();
}
View rootView = inflater.inflate(R.layout.fragment_top_rated, container, false);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.my_recycler_view);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
mRecyclerView.setHasFixedSize(true);
// use a linear layout manager
mLayoutManager = new LinearLayoutManager(getContext());
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.addItemDecoration(new DividerItemDecoration(getContext(), LinearLayoutCompat.VERTICAL));
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.addOnItemTouchListener(new CustomTouchListener(context, new onItemClickListener() {
#Override
public void onClick(View view, int index) {
mCallback.onAudioItemSelected(listToDisplay.get(index));
}
}));
mAdapter = new SongListAdapter2(listToDisplay, context);
mRecyclerView.setAdapter(mAdapter);
return rootView;
}
private void defaultList(){
listToDisplay = new ArrayList<>();
listToDisplay.add(new Audio("You need to add some songs!"));
}
#Override
public void playListChanged(ArrayList<Audio> arrayList) {
Log.d(TAG, "updateTop: in.");
if (!arrayList.isEmpty()) {
listToDisplay = arrayList;
}else {
defaultList();
}
updateListView();
Log.d(TAG, "updateTop: out.");
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
context = getContext();
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception
try {
mCallback = (AudioItemSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement AudioItemSelectedListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mCallback = null;
}
private void updateListView(){
Log.d(TAG, "updateTop: in.");
((SongListAdapter2) mAdapter).refreshList(listToDisplay);
Log.d(TAG, "updateTop: out.");
}
}
I have added refreshList():
public void refreshList(ArrayList<Audio> list) {
this.list = list;
notifyDataSetChanged();
}
And then the error message:
--------- beginning of crash
06-09 15:14:24.275 9114-9114/com.bteq.audia E/AndroidRuntime: FATAL
EXCEPTION: main
Process: com.bteq.audia, PID: 9114
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.bteq.audia.SongListAdapter2.refreshList(java.util.ArrayList)' on a null object reference
at com.bteq.audia.MainLibraryFragment.updateListView(MainLibraryFragment.java:128)
at com.bteq.audia.MainLibraryFragment.playListChanged(MainLibraryFragment.java:100)
at com.bteq.audia.MainActivity.onDialogPositiveClick(MainActivity.java:195)
at com.bteq.audia.AddSongDialog$2.onClick(AddSongDialog.java:47)
at android.support.v7.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6753)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:482)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
06-09 15:14:24.281 9114-9114/com.bteq.audia W/OPDiagnose:
getService:OPDiagnoseService NULL
The MainActivity that contains the Pager. I tried to remove as much code as I could that wasn't relevant.
public class MainActivity extends AppCompatActivity implements MainLibraryFragment.AudioItemSelectedListener, AddSongDialog.NoticeDialogListener, ShowQueueDialog.ShouldClearAll {
private MemoryManagement memoryManagement;
private ViewPager viewPager;
private com.bteq.audia.PagerAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
memoryManagement = new MemoryManagement(this);
setContentView(R.layout.activity_main);
Toolbar myToolbar = (Toolbar) findViewById(R.id.my_toolbar);
setSupportActionBar(myToolbar);
initialiseViews();
}
public void initialiseViews() {
//Fills the titles of all the tabs.
String[] tabTitles = getTabTitles();
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabLayout);
for (int i = 0; i < tabTitles.length; i++) {
tabLayout.addTab(tabLayout.newTab().setText(tabTitles[i]));
}
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
//Sets up the ViewPager and creates the functionality to make them changeable.
viewPager = (ViewPager) findViewById(R.id.pager);
adapter = new PagerAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
viewPager.setAdapter(adapter);
viewPager.addOnPageChangeListener(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) {
}
});
setupBottomView();
}
//method used as main control to the service from this activity.
private void audioActionDo(String audioAction) {
Intent intent = new Intent("audio_control_intent");
intent.putExtra("button_pressed", audioAction);
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
/*
Method tells the activity which item in the shown playlist has been selected. This should then cause that item to play if possible.
//TODO, fill in body of method.
*/
#Override
public void onAudioItemSelected(Audio audio) {
songSelected(audio);
Log.d("MainActivity", "onAudioItemSelected: At end");
}
#Override
public void onDialogPositiveClick(String titleString, String artistString, String albumString, String genreString) {
Audio audioToAdd = new Audio(genreString, titleString, albumString, artistString);
memoryManagement.addAudioToList(audioToAdd, MemoryManagement.MAIN_LIST_KEY);
Fragment fragment = adapter.getItem(0);
PlaylistChangedInterface playlistChangedInterface = (PlaylistChangedInterface) fragment;
playlistChangedInterface.playListChanged(memoryManagement.loadAudioList(MemoryManagement.MAIN_LIST_KEY));
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_top, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.action_settings:
//TODO, take the user to the app settings page.
// User chose the "Settings" item, show the app settings UI...
return true;
case R.id.action_favorite:
//TODO, make this favourite the current Audio.
// User chose the "Favorite" action, mark the current item
// as a favorite...
memoryManagement.clearPrefsValue(MemoryManagement.MAIN_LIST_KEY);
return true;
case R.id.action_add_new_song:
showAddSongDialog();
return true;
case R.id.action_show_queue:
showQueueDialog();
return true;
case R.id.action_add_from_internal:
return true;
default:
// If we got here, the user's action was not recognized.
// Invoke the superclass to handle it.
return super.onOptionsItemSelected(item);
}
}
public void showAddSongDialog() {
DialogFragment newFragment = new AddSongDialog();
newFragment.show(getSupportFragmentManager(), "missiles");
}
public void showQueueDialog() {
DialogFragment newFragment = new ShowQueueDialog();
newFragment.show(getSupportFragmentManager(), "showQueue");
}
//Should immediately play a song then be able to continue with the queued audio.
public void songSelected(Audio audioToAdd) {
}
//clears the entire queue but completes playback of current audio.
private void clearCurrentQueue() {
memoryManagement.clearPrefsValue(MemoryManagement.QUEUE_KEY);
}
// Utility method. Returns the locale titles for the tabs in the viewpager.
private String[] getTabTitles() {
return getResources().getStringArray(R.array.tab_titles);
}
#Override
public void clearAllPressed() {
clearCurrentQueue();
}
private void setupBottomView() {
ImageView playButton = (ImageView) findViewById(R.id.bottom_play);
ImageView replayButton = (ImageView) findViewById(R.id.bottom_replay);
ImageView skipBackButton = (ImageView) findViewById(R.id.bottom_skip_back);
ImageView skipForwardButton = (ImageView) findViewById(R.id.bottom_skip_next);
ImageView shuffleButton = (ImageView) findViewById(R.id.bottom_shuffle);
playButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// playAudio(storageUtility2.loadAudioIndex());
audioActionDo(getResources().getString(R.string.broadcast_action_playpause));
}
});
replayButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
audioActionDo(getResources().getString(R.string.broadcast_action_loop));
}
});
skipBackButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
audioActionDo(getResources().getString(R.string.broadcast_action_skip_back));
}
});
skipForwardButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
audioActionDo(getResources().getString(R.string.broadcast_action_skip_forward));
}
});
shuffleButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
audioActionDo(getResources().getString(R.string.broadcast_action_shuffle));
}
});
}
}
I get a null pointer exception whenever the method updateListView is called. The fragment initially displays with no problem, but when a new entry is added to the ArrayList and the updateListView is called - it stops. The log shows that mAdapter is null. I don't know enough about android yet to understand why mAdapter becomes null after it is used before.
Sorry for large amount of code but I'm completely stumped. Thanks.

In my opinion this is because your variable mAdapter is declared as of type RecyclerView.Adapter which is an interface which does not declare your method, refreshList(). Therefore if you intend to use the type RecyclerView.Adapter, only the methods declared in the interface could be called by using the reference variable. If you intend to call methods implemented by yourself other than whats overridden from the interface, the reference type SongListAdapter2 has to be used.
Simple fix is to change the RecyclerView.Adapter to SongListAdapter2 at the declaration of the mAdapter.
Ps. Check android docs to see the methods declared by the RecyclerView.Adapter.

It depends on how you are accessing the adapter in the RecyclerView. If you look at this line Fragment fragment = adapter.getItem(0), you are trying to access the first fragment in your ViewPager's adapter. getItem usually won't get called again after the ViewPager has layout its fragments which means your call to access the RecyclerView's adapter in the first fragment in the ViewPager will be pointing to a null adapter even though the fragment might exist (and you might even be calling a wrong fragment). Use this Fragment fragment = getChildFragmentManager().getFragments().get(0) to access the right fragment which will ensure the RecyclerView adapter won't be null. Change getChildFragmentManager() to getFragmentManager() if your ViewPager is in an Activity.

slider a pager from onBackPressed

I need to change the slides of my pager programmatically when backbutton is pressed in the wrapper activity, but when I call pager.setCurrentItem(1) inside the onBackPressed the application is being closed.
Code:
public class MainActivity extends FragmentActivity {
static final int NUM_ITEMS = 3;
static int fSelected = 1;
MyAdapter mAdapter;
ViewPager mPager;
// ADAPTER
public static class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
#Override
public int getCount() {
return NUM_ITEMS;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return FirstFragment.init(position);
case 1:
return SecondFragment.init(position);
case 2:
return ThirdFragment.init(position);
default:
return null;
}
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Context mContext = getApplicationContext();
playAppearAnimation(mContext);
// ANIM
playAppearAnimation(getApplicationContext());
final ViewPager mPager = findViewById(R.id.pager);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager.setAdapter(mAdapter);
mPager.setCurrentItem(1);
//disabilita lo scroll by touch0
mPager.setOnTouchListener(new View.OnTouchListener()
{
#Override
public boolean onTouch(View v, MotionEvent event)
{
return false;
}
});
// BACK TO RETRIEVE PASSWORD
TextView button = (TextView)findViewById(R.id.lost_password);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mPager.setCurrentItem(0);
}
});
/*
button = (Button)findViewById(R.id.goto_last);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {+
mPager.setCurrentItem(NUM_ITEMS-1);
}
});*/
// ANIMAZIONE DEL RECUPERA PASSWORD
mPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
public void onPageScrollStateChanged(int state) {}
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
public void onPageSelected(int position) {
// NASCONDO LOST PASSWORD
View lostPassword = (TextView)findViewById(R.id.lost_password);
//Toast.makeText(getApplicationContext(),""+position, Toast.LENGTH_LONG).show();
//>> HIDE / UNHIDE lost password
switch(position){
case 0:
fSelected = 0;
lostPassword.startAnimation(AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_out));
break;
case 1:
fSelected = 1;
lostPassword.startAnimation(AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_in));
break;
case 2:
fSelected = 2;
lostPassword.startAnimation(AnimationUtils.loadAnimation(getApplicationContext(), R.anim.fade_out));
break;
}
}
});
}
public void playAppearAnimation(Context context){
ImageView logo = findViewById(R.id.logo);
ImageView logotype = findViewById(R.id.logotype);
logo.startAnimation(AnimationUtils.loadAnimation(context, R.anim.logo_anim));
logotype.startAnimation(AnimationUtils.loadAnimation(context, R.anim.logo_anim));
com.ubris.design.test1.NonSwipeableViewPager pager = findViewById(R.id.pager);
pager.startAnimation(AnimationUtils.loadAnimation(context, R.anim.anim_fragments));
}
#Override
public void onBackPressed() {
mPager.setCurrentItem(0);
}
Logcat:
java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.support.v4.view.ViewPager.setCurrentItem(int)' on a null
object reference
at com.ubris.design.test1.MainActivity.onBackPressed(MainActivity.java:155)
at android.app.Activity.onKeyUp(Activity.java:2826)
at android.view.KeyEvent.dispatch(KeyEvent.java:2766)
at android.app.Activity.dispatchKeyEvent(Activity.java:3146)
at com.android.internal.policy.DecorView.dispatchKeyEvent(DecorView.java:353)
at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:4742)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4713)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4249)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4302)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4268)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4395)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4276)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4452)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4249)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4302)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4268)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4276)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4249)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4302)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4268)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4428)
at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:4589)
at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2512)
at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:2106)
at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:2097)
at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:2487)
at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:356)
at android.os.Looper.loop(Looper.java:138)
at android.app.ActivityThread.main(ActivityThread.java:6523)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:942)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:832)italic

Remove super.onBackPressed() from the code - that's what usually closes the app in such case.
UPD.: as you posted the code, the problem is clear now.
Change final ViewPager mPager = findViewById(R.id.pager); to mPager = findViewById(R.id.pager); to assign its value instead of creating local variable.

android reset/reload fragment data

I use a ViewPager to create 3 Fragments on Activity_1, this is the ViewPagerAdapter:
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public ViewPagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
Fragment1 tab1 = new Fragment1();
return tab1;
case 1:
Fragment2 tab2 = new Fragment2();
return tab2;
case 2:
Fragment3 tab3 = new Fragment3();
return tab3;
default:
return null;
}
}
#Override
public int getCount() {
return mNumOfTabs;
}
}
This is Activity_1 which holds all Fragments, and automatically shows Fragment_1 when Activity_1 is opened :
public class Activity1 extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_1);
TabLayout tab_layout = (TabLayout) findViewById(R.id.tab_layout);
tab_layout.addTab(tab_layout.newTab().setText("Frag1"));
tab_layout.addTab(tab_layout.newTab().setText("Frag2"));
tab_layout.addTab(tab_layout.newTab().setText("Frag3"));
final ViewPager view_pager = (ViewPager) findViewById(R.id.viewpager);
final ViewPagerAdapter adapter = new ViewPagerAdapter
(getSupportFragmentManager(), tab_layout.getTabCount());
view_pager.setAdapter(adapter);
view_pager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tab_layout));
tab_layout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
view_pager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
Every Fragment can go to Activity_2.
Fragment_3 holds data that can be edited on Activity_2.
My Problem:
When edit data from Activity_2 and back to Activity_1 using the back button,
data in Fragment_3 is still old, not changed with the edited data from Activity_2.
But when close Activity_1 and open it again, data in Fragment_3 is changed.
I think I need reset or reload Fragment_3 when I come back to Activity_1 from Activity_2, but I don't know how.
update,
this is Activity_2:
public class Activity2 extends AppCompatActivity {
TextView tv_id;
String id;
TextView tv_d;
Button bt_add, bt_remove;
String str_find;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_2);
Intent i = getIntent();
id = i.getStringExtra("id");
tv_id = (TextView)findViewById(R.id.tv_DetailId);
tv_id.setText(id);
tv_d = (TextView)findViewById(R.id.tv_Detail);
bt_add = (Button)findViewById(R.id.bt_detail_add);
bt_remove = (Button)findViewById(R.id.bt_detail_remove);
str_find = "example";
try {
final File file = new File(Environment.getExternalStorageDirectory() + "/TestFolder/Test.txt");
StringBuilder text = new StringBuilder();
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null) {
text.append(line);
text.append('\n');
}
br.close();
xml_root = text.toString();
FileInputStream in = new FileInputStream(file);
int len = 0;
byte[] data1 = new byte[1024];
while ( -1 != (len = in.read(data1)) ){
if(new String(data1, 0, len).contains(str_find)){
bt_add.setVisibility(View.GONE);
tv_d.setText("yes");
bt_remove.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//something to edit data on Test.txt
}
});
}
else {
bt_remove.setVisibility(View.GONE);
tv_d.setText("no");
bt_add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//something to edit data on Test.txt
}
});
}
}
}
catch (Exception e){
e.printStackTrace();
}
}
}

in your onResume() method you can have a condition check
view_pager.setCurrentItem(last_frag);
where last_frag is a global integer whose value you set everytime in on page change listener.
this will refresh your fragment.
In your Activity1.java
make the following changes
private ViewPager view_pager; will be your global variable
and remove final ViewPager during initialization.
Make it like this in onCreate() Method
view_pager = (ViewPager) findViewById(R.id.viewpager);
private int last_frag = 0; will be your global variable in Activity1.java
#Override
public void onTabSelected(TabLayout.Tab tab) {
view_pager.setCurrentItem(tab.getPosition());
last_frag = tab.getPosition();
}