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android fragment view throw null pointer exception even after being initialized in onCreateView

here i have a fragment interaction, where if recycler view item get clicked it passed data to MainActivity and then MainActivity call DetailFragment.updateText() method to update it's view but the views are not initialized even though i did that in onViewCreated(), if DetailFragment.updateText() is getting called before views are initialized then how can i make sure they get called after views have been initialized.
* note i added the DetailFragment to a DetailActivity through XML fragment tag, and the same for ListFragment and MainActivity
MainActivity
public class MainActivity extends AppCompatActivity implements ListFragment.Listener {
// the method to be called when an item in recycler view is clicked
// so i can pass this data to DetailFragment
#Override
public void listenerMethod(String firstName, String lastName) {
DetailFragment detailFragment = new DetailFragment();
detailFragment.updateText(firstName, lastName);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
ListFragment
public class ListFragment extends Fragment {
private static final String TAG = "ListFragment";
private RecyclerView recyclerView;
private RecyclerViewAdapter recyclerViewAdapter;
// fragment communication interface
public interface Listener {
void listenerMethod(String firstName, String lastName);
}
private Listener listener;
#Override
public void onAttach(#NonNull Context context) {
super.onAttach(context);
try {
this.listener = (Listener) context;
} catch (ClassCastException e) {
Log.d(TAG, "onAttach: "+ e.getMessage());
}
}
public ListFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_list, container, false);
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
recyclerView = getView().findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
// some dummy data to fill the recycler view
ArrayList<User> users = new ArrayList<>();
users.add(new User("hiwa", "jalal"));
users.add(new User("mohammed", "abdullah"));
recyclerViewAdapter = new RecyclerViewAdapter(users, getActivity(), listener);
recyclerView.setAdapter(recyclerViewAdapter);
}
}
RecyclerViewAdapter
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
private List<User> userList;
private Context context;
private ListFragment.Listener listener;
public RecyclerViewAdapter(List<User> userList, Context context, ListFragment.Listener listener) {
this.userList = userList;
this.context = context;
this.listener = listener;
}
#NonNull
#Override
public ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.user_row
, parent, false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int position) {
User user = userList.get(position);
holder.tvFirstName.setText(user.getFirstName());
holder.tvLastName.setText(user.getLastName());
}
#Override
public int getItemCount() {
return userList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public TextView tvFirstName;
public TextView tvLastName;
public ViewHolder(#NonNull View itemView) {
super(itemView);
tvFirstName = itemView.findViewById(R.id.row_first_name);
tvLastName = itemView.findViewById(R.id.row_last_name);
itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
User user = userList.get(getAdapterPosition);
listener.listenerMethod(user.getFirstName(), user.getLastName());
}
});
}
}
}
DetailFragment
public class DetailFragment extends Fragment {
private TextView tvFirstName;
private TextView tvLastName;
public DetailFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_detail, container, false);
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
tvFirstName = view.findViewById(R.id.detail_frag_first_name);
tvLastName = view.findViewById(R.id.detail_frag_last_name);
}
// update the details fragment views
public void updateText(String firstName, String lastName) {
tvFirstName.setText(firstName);
tvLastName.setText(lastName);
}
}
activity_main
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<fragment
android:id="#+id/main_fragment_list"
android:name="com.example.peacewithfragments.ListFragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
activity_detail
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".DetailsActivity">
<fragment
android:id="#+id/detailsActivity_fragment_container"
android:name="com.example.peacewithfragments.DetailFragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>

You create a new instance of the DetialsFragment every time you trigger the method of your listener. If you have defined the fragment in your layout xml, you must get the correct instance of the fragment from the fragmentmanager (or supportFragmentManager as you are using AppCompatActivity.
#Override
public void listenerMethod(String firstName, String lastName) {
// find the fragment by its id, sometihng like that
// id is the fragments id you defined in the layout xml
DetailsFragment detailFragment = (DetailsFragment)supportFragmentManager.findFragementById(R.id.frag_details);
detailFragment.updateText(firstName, lastName);
}

You can't directly access DetailFragment from your MainActivity as it's not part of MainActivity. So, first you have to navigate to DetailActivity and then access DetailFragment. Check below:
public class MainActivity extends AppCompatActivity implements ListFragment.Listener {
private DetailFragment detailFragment;
#Override
public void listenerMethod(String firstName, String lastName) {
if(detailFragment != null) {
detailFragment.updateText(firstName, lastName);
} else {
Intent detailIntent = new Intent(this, DetailsActivity.class);
detailIntent.putExtra("FirstName", firstName);
detailIntent.putExtra("LastName", lastName);
startActivity(detailIntent);
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View view = findViewById(R.id.tablet_detail_container);
if (view != null) {
detailFragment = new DetailFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.add(R.id.tablet_detail_container, detailFragment);
transaction.addToBackStack(null);
transaction.commit();
}
}
}
Then in your DetailsActivity accept those extra and pass it to DetailFragment like below:
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail);
...
String firstName = getIntent().getStringExtra("FirstName");
String lastName = getIntent().getStringExtra("LastName");
DetailFragment detailFragment = getSupportFragmentManager().findFragmentById(R.id.detailsActivity_fragment_container);
if(detailFragment != null)
detailFragment.updateText(firstName, lastName);
}

getItem function calling twice in FragmentStatePagerAdapter?

I Have a problem with getItem() function why because it is called twice in FragmentStatePagerAdapter class.
Actually the main reason is in application having TextoSpeech functionality so getItem() function twice the text also speech twice. This is my code can u please assist me....Great thanks in advance.
Here is the code
This is MainActivity class:
public class MainActivity extends FragmentActivity{
PagerFragment pagerFragment;
Cursor mCursor;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.rhymes_activity_main);
DBUtils utils = new DBUtils(getApplicationContext());
new DBUtils(getApplicationContext());
try {
DBUtils.createDatabase();
} catch (IOException e) {
Log.w(" Create Db "+e.toString(),"===");
}
DBUtils.openDatabase();
mCursor = utils.getResult("select * from Cflviewpagerdata order by title");
final ArrayList<PageData> myList = new ArrayList<PageData>();
while (mCursor.moveToNext()) {
myList.add(new PageData(mCursor.getInt(
mCursor.getColumnIndex("_id")),
mCursor.getString(mCursor.getColumnIndex("title")),
mCursor.getString(mCursor.getColumnIndex("view"))));
}
mCursor.close();
ListView lv = (ListView) findViewById(R.id.list_view);
ListViewAdapter lva = new ListViewAdapter(this, R.layout.list_item, myList);
lv.setAdapter(lva);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//peace of code that create launch new fragment with swipe view inside
PagerFragment pagerFragment = new PagerFragment();
Bundle bundle = new Bundle();
bundle.putInt("CURRENT_POSITION", position);
bundle.putParcelableArrayList("DATA_LIST", myList);
pagerFragment.setArguments(bundle);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction ft = fragmentManager.beginTransaction();
ft.replace(R.id.container, pagerFragment, "swipe_view_fragment").commit();
}
});
DBUtils.closeDataBase();
}
#Override
public void onBackPressed() {
FragmentManager fm = getSupportFragmentManager();
Fragment f = fm.findFragmentByTag("swipe_view_fragment");
if(f!=null){
fm.beginTransaction().remove(f).commit();
}else{
super.onBackPressed();
}
}
}
This is PagerFragment class:
public class PagerFragment extends Fragment{
private ArrayList<PageData> data;
private int currentPosition;
private String mTitle;
private FragmentActivity context;
#Override public void onAttach(Activity activity) {
context = (FragmentActivity) activity;
super.onAttach(activity);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_pager, container, false);
ViewPager mViewPager = (ViewPager) v.findViewById(R.id.pager_view);
currentPosition = getArguments().getInt("CURRENT_POSITION");
mTitle = getArguments().getString("T_TITLE");
data = getArguments().getParcelableArrayList("DATA_LIST");
FragmentItemPagerAdapter fragmentItemPagerAdapter = new FragmentItemPagerAdapter(getFragmentManager(), data);
mViewPager.setAdapter(fragmentItemPagerAdapter);
mViewPager.setCurrentItem(currentPosition);
return v;
}
}
This is FragmentItemPagerAdapter class:
public class FragmentItemPagerAdapter extends FragmentStatePagerAdapter{
private static ArrayList<PageData> data;
public FragmentItemPagerAdapter(FragmentManager fm, ArrayList<PageData> data){
super(fm);
this.data = data;
}
#Override
public Fragment getItem(int position) {
Fragment fragment = new PageFragment();
Bundle args = new Bundle();
args.putString(PageFragment.TITLE, data.get(position).getTitle());
args.putString(PageFragment.DESCRIPTION, data.get(position).getDes());
args.putInt("CURRENT_POSITION", position);
fragment.setArguments(args);
return fragment;
}
void deletePage(int position) {
if (canDelete()) {
data.remove(position);
notifyDataSetChanged();
}
}
boolean canDelete() {
return data.size() > 0;
}
#Override
public int getItemPosition(Object object) {
// refresh all fragments when data set changed
return PagerAdapter.POSITION_NONE;
}
#Override
public int getCount() {
return data.size();
}
public static class PageFragment extends Fragment implements OnInitListener{
public static final String TITLE = "title";
public static final String DESCRIPTION = "view";
String om;
TextToSpeech tts;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_item, container, false);
((TextView) rootView.findViewById(R.id.item_label)).setText(getArguments().getString(TITLE));
View tv = rootView.findViewById(R.id.item_des);
((TextView) tv).setText(getArguments().getString(DESCRIPTION));
Bundle bundle = getArguments();
int currentPosition = bundle.getInt("CURRENT_POSITION");
tts = new TextToSpeech( getActivity(), PageFragment.this);
om = data.get(currentPosition).getDes();
tts.speak(om, TextToSpeech.QUEUE_FLUSH, null);
return rootView;
}
#Override
public void onDestroy() {
if (tts != null) {
tts.stop();
tts.shutdown();
}
super.onDestroy();
}
public void onInit(int status) {
// TODO Auto-generated method stub
if (status == TextToSpeech.SUCCESS) {
tts.speak(om, TextToSpeech.QUEUE_FLUSH, null);
}
}
}
}
This is PageData class:
This class is Object class
public class PageData implements Parcelable{
private String title;
private String view;
public PageData(){
}
public PageData(Parcel in){
title = in.readString();
view = in.readString();
}
public int describeContents() {
return 0;
}
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(title);
dest.writeString(view);
}
public PageData(int picture, String title, String description){
this.title = title;
this.view = description;
}
public String getTitle() {
return title;
}
public String getDes() {
return view;
}
}
This is Xml code
fragment_item.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="8dp"
android:orientation="vertical">
<TextView
android:id="#+id/item_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginTop="10sp"
android:text="Image Name"
android:textColor="#android:color/black"
android:textSize="18sp"
android:layout_gravity="center_horizontal" />
<TextView
android:id="#+id/item_des"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginTop="10sp"
android:text="Image Name"
android:textColor="#android:color/black"
android:textSize="18sp"
android:layout_gravity="center_horizontal" />
</LinearLayout>
This is fragment_pager.xml: This is viewpager layout
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ffffff">
<android.support.v4.view.ViewPager
android:id="#+id/pager_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
This is rhymes_activity_main.xml: This is for listview of application.
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView android:scrollbarAlwaysDrawVerticalTrack="true"
android:id="#+id/list_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</FrameLayout>
This images are my application look
This image is logcat of my application
Highlighted is my problem.
This is my code can you please help me any one.
I am new one of Android so please help

FragmentStatePagerAdapter preloads always at least 1 page.
You can try to use setUserVisibleHint to handle your logic only for visible fragment:
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
// Your code
}
}

Android Shared Element Transitions between two ViewPagers

I'm trying to achieve the following:
I have an item view that displays a ViewPager with images of that item and some other information. When the user taps one of the ViewPager's images, I'd like there to be a transition between the image on the first screen and the same image on another ViewPager in a new Activity.
So far, I've managed to get the basic functionality working but there are a couple of key things that do not work as expected:
The transition from ViewPager A to the second Activity with ViewPager B only works when tapping the image at index 0 or 1 in ViewPager A.
There is a return animation when pressing back from ViewPager B in the new Activity - as long as I do not swipe to another image so the transition is from the full screen mode I'd be displaying in ViewPager B to the same image in ViewPager A. When swiping to another image and pressing back - there's no animation.
Number 1 is happening because the first couple of pages of the ViewPager are instantiated when it's created so the instantiateItem method of the Adapter gets called for each of these and this is where I'm setting the transitionName.
This is proven by the fact that calling this on the ViewPager makes that issue go away and the entry animation works on all screens:
detailPager.setOffscreenPageLimit(largeNumber);
Obviously this is unsustainable, I'd much rather not have such a high off screen limit.
My question is twofold:
How do I achieve the animation for each ViewPager item without keeping all the pages in memory via the above hack?
How can I ensure that a return transition takes place when swiping to another page in ViewPager B?
I've included my code below:
ItemActivity
public class ItemActivity extends AppCompatActivity {
private static final String ITEM_TAG = "item_tag";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_with_fragment_container);
ButterKnife.bind(this);
if (savedInstanceState == null) {
attachFragment();
}
}
private void attachFragment() {
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_container, ItemFragment.newInstance(), ITEM_TAG)
.commit();
}
#Override
public void onActivityReenter(int resultCode, Intent data) {
super.onActivityReenter(resultCode, data);
ItemFragment fragment = (ItemFragment) getSupportFragmentManager().findFragmentByTag(ITEM_TAG);
if (fragment != null) {
fragment.onReenter(data);
}
}}
ItemFragment - This is where the first ViewPager is
public class ItemFragment extends Fragment implements MyAdapter.MyListener {
public static final String EXTRA_STARTING_ALBUM_POSITION = "extra_starting_item_position";
public static final String EXTRA_CURRENT_ALBUM_POSITION = "extra_current_item_position";
public static final String[] IMAGE_NAMES = {"One", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten"};
private static final int FULL_SCREEN_CODE = 1234;
private Unbinder unbinder;
private Bundle tempReenterState;
private final SharedElementCallback callback = new SharedElementCallback() {
#Override
public void onMapSharedElements(List<String> names, Map<String, View> sharedElements) {
if (tempReenterState != null) {
int startingPosition = tempReenterState.getInt(EXTRA_STARTING_ALBUM_POSITION);
int currentPosition = tempReenterState.getInt(EXTRA_CURRENT_ALBUM_POSITION);
if (startingPosition != currentPosition) {
String newTransitionName = IMAGE_NAMES[currentPosition];
View newSharedElement = detailPager.findViewWithTag(newTransitionName);
if (newSharedElement != null) {
names.clear();
names.add(newTransitionName);
sharedElements.clear();
sharedElements.put(newTransitionName, newSharedElement);
}
}
tempReenterState = null;
} else {
View navigationBar = getActivity().findViewById(android.R.id.navigationBarBackground);
View statusBar = getActivity().findViewById(android.R.id.statusBarBackground);
if (navigationBar != null) {
names.add(navigationBar.getTransitionName());
sharedElements.put(navigationBar.getTransitionName(), navigationBar);
}
if (statusBar != null) {
names.add(statusBar.getTransitionName());
sharedElements.put(statusBar.getTransitionName(), statusBar);
}
}
}
};
private List<String> images = Arrays.asList("http://wowslider.com/sliders/demo-9/data/images/1293441583_nature_forest_morning_in_the_forest_015232_.jpg",
"http://wowslider.com/sliders/demo-18/data1/images/hongkong1081704.jpg",
"http://www.irishtimes.com/polopoly_fs/1.2614603.1461003507!/image/image.jpg_gen/derivatives/box_620_330/image.jpg",
"http://weknowyourdreams.com/images/sky/sky-05.jpg");
#BindView(R.id.detail_pager)
ViewPager detailPager;
public static ItemFragment newInstance() {
return new ItemFragment();
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_image_detail, container, false);
unbinder = ButterKnife.bind(this, view);
return view;
}
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ActivityCompat.setExitSharedElementCallback(getActivity(), callback);
detailPager.setAdapter(new MyAdapter(getActivity(), images, this));
}
#Override
public void goFullScreen(final int position, View view) {
Intent intent = FullScreenActivity.newIntent(getActivity(), position, images);
startActivityForResult(intent, FULL_SCREEN_CODE, ActivityOptions.makeSceneTransitionAnimation(getActivity(), view, view.getTransitionName()).toBundle());
}
public void onReenter(Intent data) {
tempReenterState = new Bundle(data.getExtras());
int startingPosition = tempReenterState.getInt(EXTRA_STARTING_ALBUM_POSITION);
int currentPosition = tempReenterState.getInt(EXTRA_CURRENT_ALBUM_POSITION);
if (startingPosition != currentPosition) {
detailPager.setCurrentItem(currentPosition, false);
}
ActivityCompat.postponeEnterTransition(getActivity());
detailPager.post(new Runnable() {
#Override
public void run() {
ActivityCompat.startPostponedEnterTransition(getActivity());
}
});
}
#Override
public void onDestroyView() {
super.onDestroyView();
if (unbinder != null) {
unbinder.unbind();
}
}
}
FullScreenActivity - This is where the second ViewPager is housed
public class FullScreenActivity extends AppCompatActivity {
private final SharedElementCallback callback = new SharedElementCallback() {
#Override
public void onMapSharedElements(List<String> names, Map<String, View> sharedElements) {
if (mIsReturning) {
if (currentImage == null) {
// If shared element is null, then it has been scrolled off screen and
// no longer visible. In this case we cancel the shared element transition by
// removing the shared element from the shared elements map.
names.clear();
sharedElements.clear();
} else if (selectedIndex != mCurrentPosition) {
// If the user has swiped to a different ViewPager page, then we need to
// remove the old shared element and replace it with the new shared element
// that should be transitioned instead.
names.clear();
names.add(currentImage.getTransitionName());
sharedElements.clear();
sharedElements.put(currentImage.getTransitionName(), currentImage);
}
}
}
};
private boolean mIsReturning;
private int mCurrentPosition;
private int selectedIndex;
private static final String ARG_PRESELECTED_INDEX = "arg_preselected_index";
private static final String ARG_GALLERY_IMAGES = "arg_gallery_images";
public static final String KEY_SELECTED_IMAGE_INDEX = "key_selected_image_index";
public static final String KEY_RETAINED_IMAGES = "key_retained_images";
private static final int DEFAULT_SELECTED_INDEX = 0;
private List<String> images;
private ImageAdapter adapter;
private ImageView currentImage;
#BindView(R.id.full_screen_pager)
ViewPager viewPager;
public static Intent newIntent(#NonNull final Context context, final int selectedIndex, #NonNull final List<String> images) {
Intent intent = new Intent(context, FullScreenActivity.class);
intent.putExtra(ARG_PRESELECTED_INDEX, selectedIndex);
intent.putStringArrayListExtra(ARG_GALLERY_IMAGES, new ArrayList<>(images));
return intent;
}
#CallSuper
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_full_screen);
ButterKnife.bind(this);
ActivityCompat.postponeEnterTransition(this);
ActivityCompat.setExitSharedElementCallback(this, callback);
if (savedInstanceState == null) {
selectedIndex = getIntent().getIntExtra(ARG_PRESELECTED_INDEX, 0);
mCurrentPosition = selectedIndex;
images = getIntent().getStringArrayListExtra(ARG_GALLERY_IMAGES);
} else {
selectedIndex = savedInstanceState.getInt(KEY_SELECTED_IMAGE_INDEX);
images = savedInstanceState.getStringArrayList(KEY_RETAINED_IMAGES);
}
setupViewPager(selectedIndex, images);
}
private void setupViewPager(final int selectedIndex, List<String> images) {
adapter = new ImageAdapter(this, images);
viewPager.post(new Runnable() {
#Override
public void run() {
viewPager.setAdapter(adapter);
viewPager.setCurrentItem(selectedIndex);
viewPager.addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
#Override
public void onPageSelected(int position) {
mCurrentPosition = position;
}
});
ActivityCompat.startPostponedEnterTransition(FullScreenActivity.this);
}
});
}
#Override
public void finishAfterTransition() {
mIsReturning = true;
Intent data = new Intent();
data.putExtra(EXTRA_STARTING_ALBUM_POSITION, selectedIndex);
data.putExtra(EXTRA_CURRENT_ALBUM_POSITION, viewPager.getCurrentItem());
setResult(RESULT_OK, data);
super.finishAfterTransition();
}
private class ImageAdapter extends PagerAdapter {
private final LayoutInflater layoutInflater;
private final List<String> images;
private ImageLoader<ImageView> imageLoader;
public ImageAdapter(Context context, List<String> images) {
this.imageLoader = new PicassoImageLoader(context);
this.images = images;
this.layoutInflater = LayoutInflater.from(context);
}
#Override
public int getCount() {
return images.size();
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
final ImageView imageView = (ImageView) layoutInflater.inflate(R.layout.full_image, container, false);
imageView.setTransitionName(IMAGE_NAMES[position]);
imageView.setTag(IMAGE_NAMES[position]);
imageLoader.loadImage(images.get(position), imageView);
container.addView(imageView);
return imageView;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((ImageView) object);
}
#Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
super.setPrimaryItem(container, position, object);
currentImage = (ImageView) object;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
}
}
MyAdapter
public class MyAdapter extends PagerAdapter {
private final LayoutInflater layoutInflater;
private final List<String> images;
private final MyListener listener;
private ImageLoader<ImageView> imageLoader;
public interface MyListener {
void goFullScreen(final int position, View selected);
}
public MyAdapter(Context context, List<String> images, MyListener listener) {
this.imageLoader = new PicassoImageLoader(context);
this.layoutInflater = LayoutInflater.from(context);
this.images = images;
this.listener = listener;
}
#Override
public int getCount() {
return images.size();
}
#Override
public Object instantiateItem(ViewGroup container, final int position) {
final ImageView imageView = (ImageView) layoutInflater.inflate(R.layout.pager_item_image_thing, container, false);
imageView.setTransitionName(IMAGE_NAMES[position]);
imageView.setTag(IMAGE_NAMES[position]);
if (listener != null) {
imageView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
listener.goFullScreen(position, imageView);
}
});
}
imageLoader.loadImage(images.get(position), imageView);
container.addView(imageView);
return imageView;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((ImageView) object);
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
}
ImageLoader
public interface ImageLoader<T extends ImageView> {
void loadImage(#NonNull final Uri imageSource, #NonNull final T imageView);
void loadImage(#NonNull final String imageSource, #NonNull final T imageView);
}
PicassoImageLoader
public class PicassoImageLoader implements ImageLoader {
private final Context context;
public PicassoImageLoader(#NonNull final Context context) {
this.context = context;
}
#Override
public void loadImage(#NonNull Uri imageSource, #NonNull ImageView imageView) {
Picasso.with(context).load(imageSource).into(imageView);
}
#Override
public void loadImage(#NonNull String imageSource, #NonNull ImageView imageView) {
Picasso.with(context).load(imageSource).into(imageView);
}
}
XML Layouts
fragment_image_detail.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v4.view.ViewPager
android:id="#+id/detail_pager"
android:layout_width="match_parent"
android:layout_height="390dp" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="This is the title"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Some other descriptive text about things"/>
</LinearLayout>
layout_full_screen.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v4.view.ViewPager
android:id="#+id/full_screen_pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
pager_item_thing.xml
<?xml version="1.0" encoding="utf-8"?>
<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/pager_item_image"
android:layout_width="match_parent"
android:layout_height="200dp"
android:foreground="?android:attr/selectableItemBackgroundBorderless"
android:layout_marginBottom="16dp" />
full_image.xml
<?xml version="1.0" encoding="utf-8"?>
<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/full_image_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" />

Why PagerAdapter inside fragment shows only the first view?

This is my PagerAdapter.
public class SlideAdapter extends PagerAdapter{
private List<ImageView> views;
public SlideAdapter (List<ImageView> views){
this.views=views;
}
#Override
public void destroyItem(View container, int position, Object object) {
((ViewPager) container).removeView(views.get(position));
}
#Override
public int getCount() {
return views.size();
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view==object;
}
#Override
public Object instantiateItem(View container, int position) {
((ViewPager) container).addView(views.get(position));
return views.get(position);
}
}
This is my fragment.
public class sportfragment extends Fragment {
private ViewPager slideviewpager;
private Boolean isContinue=true;
private AtomicInteger what=new AtomicInteger (0);
private ImageView[] indiimageview;
private List<ImageView> pics;
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public sportfragment() {
}
public static sportfragment newInstance(String param1, String param2) {
sportfragment fragment = new sportfragment();
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) {
View view=inflater.inflate(R.layout.fragment_sportfragment, container, false);
slideviewpager=(ViewPager) view.findViewById(R.id.slideviewpager);
ViewGroup indicatorgroup=(ViewGroup) view.findViewById(R.id.indicatorgroup);
pics=new ArrayList<ImageView>();
ImageView slide1=new ImageView(view.getContext());
slide1.setBackgroundResource(R.drawable.slide1);
pics.add(slide1);
ImageView slide2=new ImageView(view.getContext());
slide1.setBackgroundResource(R.drawable.slide2);
pics.add(slide2);
ImageView slide3=new ImageView(view.getContext());
slide1.setBackgroundResource(R.drawable.slide3);
pics.add(slide3);
ImageView slide4=new ImageView(view.getContext());
slide1.setBackgroundResource(R.drawable.slide4);
pics.add(slide4);
indiimageview=new ImageView[pics.size()];
for (int i=0;i<pics.size();i++) {
ImageView buff=new ImageView(view.getContext());
buff.setLayoutParams(new LinearLayout.LayoutParams(20,20));
buff.setPadding(5,5,5,5);
indiimageview[i]=buff;
if (i==0) {
indiimageview[i].setBackgroundResource(R.drawable.focus);
}else {
indiimageview[i].setBackgroundResource(R.drawable.blur);
}
indicatorgroup.addView(indiimageview[i]);
}
slideviewpager.setAdapter(new SlideAdapter(pics));
slideviewpager.setOnPageChangeListener(new GuidePageChangeListener());
return view;
}
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
private final class GuidePageChangeListener implements ViewPager.OnPageChangeListener{
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
for (int i=0;i<indiimageview.length;i++) {
if (i==position) {
//4 points change with viewpager
indiimageview[i].setBackgroundResource(R.drawable.focus);
} else {
indiimageview[i].setBackgroundResource(R.drawable.blur);
}
}
}
#Override
public void onPageScrollStateChanged(int state) {
}
}
}
First page is the Image.
But other 3 is blank.
Is there any way to solve this?

ViewPagers are meant to be used with fragments, not views. This means that you should be packaging your ImageViews as Fragments rather than plain old views.
Consider the following example:
MyImageView.java
public class MyImageFragment extends Fragment {
private ImageView mImageView;
private int resourceId;
public static MyImageFragment newInstance(int resourceId) {
MyImageFragment fragment = new MyImageFragment();
Bundle args = new Bundle();
args.putInt("resource_id", resourceId);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final Bundle args = getArguments();
if (args != null && !loadedFromArgs) {
url = (String)args.getSerializable("url");
resourceId = args.getInt("in_list", -1);
loadedFromArgs = true;
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ViewGroup rootView = (ViewGroup) inflater.inflate(
R.layout.fragment_my_image, container, false);
mImageView = (ImageView) rootView.findViewById(R.id.image);
mImageView.setBackgroundDrawable(getResources().getDrawable(resourceId))
return rootView;
}
}
fragment_my_image.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="#+id/image"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scaleType="fitCenter"
android:adjustViewBounds="true"
android:layout_alignParentTop="true"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"/>
</RelativeLayout>
Now, instead of a list of ImageViews, you will have a list of MyImageFragments that your PagerAdapter will point to.

Android saving dynamically added viewpager's fragment while coming back from another activity and reopening app

With the help of answer of the this question in StackOverflow(Remove Fragment Page from ViewPager in Android), I successfully created my project and did some modifications according to my needs.
I am able to add N number of fragments(viewpages) in my main layout and delete them until page count becomes zero.
Now, I struck with an issue.i.e. ones, if I move from my current activity which is holding this pages to other activity or if I close my app and come back,I am only able to see initial statically added fragment.
I would like to see not only initial page but also previously added pages. Should i use SharedPreferences to store dynamically added fragments?
Here is my source code:
My main layout:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<android.support.v4.view.ViewPager
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="900dp"
/>
<Button
android:id="#+id/show_items"
android:layout_width="40dp"
android:layout_height="wrap_content"
android:layout_marginTop="200dp"
android:textColor="#ffffff"
android:background="#49a942"
android:textAppearance="?android:attr/textAppearanceLarge"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:text="+" />
<Button
android:id="#+id/grid_apps_show"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/pager"
android:layout_alignParentBottom="true"
android:text="Apps"
/>
</RelativeLayout>
My MainActivity class:
public class MainActivity extends FragmentActivity implements TextProvider{
Button home;
private ViewPager mPager;
private MyPagerAdapter mAdapter;
private ArrayList<String> mEntries = new ArrayList<String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
home = (Button) findViewById(R.id.show_items);
mEntries.add("pos 1");
mPager = (ViewPager) findViewById(R.id.pager);
home.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
MainActivity.this);
alertDialogBuilder.setTitle("Add/Delete Screens");
alertDialogBuilder
.setCancelable(false)
.setNegativeButton("+",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
addNewItem();
}
})
.setPositiveButton("-",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
removeCurrentItem();
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
});
mAdapter = new MyPagerAdapter(this.getSupportFragmentManager(), this);
mPager.setAdapter(mAdapter);
}
private void addNewItem() {
mEntries.add("Pages");
mAdapter.notifyDataSetChanged();
}
private void removeCurrentItem() {
int position = mPager.getCurrentItem();
if(position != 0){
mEntries.remove(position);
mAdapter.notifyDataSetChanged();
}
else{
Toast.makeText(getApplicationContext(), "Minimum Screens are one!", Toast.LENGTH_LONG).show();
}
}
#Override
public String getTextForPosition(int position) {
return mEntries.get(position);
}
#Override
public int getCount() {
return mEntries.size();
}
private class MyPagerAdapter extends FragmentPagerAdapter {
private TextProvider mProvider;
private long baseId = 0;
public MyPagerAdapter(FragmentManager fm, TextProvider provider) {
super(fm);
this.mProvider = provider;
}
#Override
public Fragment getItem(int position) {
if(position == 0){
return ScreenOne.newInstance(mProvider.getTextForPosition(position));
}
if(position == 1){
return ScreenTwo.newInstance(mProvider.getTextForPosition(position));
}
return ScreenTwo.newInstance(mProvider.getTextForPosition(position));
}
#Override
public int getCount() {
return mProvider.getCount();
}
//this is called when notifyDataSetChanged() is called
#Override
public int getItemPosition(Object object) {
// refresh all fragments when data set changed
return PagerAdapter.POSITION_NONE;
}
#Override
public long getItemId(int position) {
// give an ID different from position when position has been changed
return baseId + position;
}
/**
* Notify that the position of a fragment has been changed.
* Create a new ID for each position to force recreation of the fragment
* #param n number of items which have been changed
*/
public void notifyChangeInPosition(int n) {
// shift the ID returned by getItemId outside the range of all previous fragments
baseId += getCount() + n;
}
}
}
my fragment one:
public class ScreenOne extends Fragment {
private String mText;
public static ScreenOne newInstance(String text) {
ScreenOne f = new ScreenOne(text);
return f;
}
public ScreenOne() {
}
public ScreenOne(String text) {
this.mText = text;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.screen_one, container, false);
((TextView) root.findViewById(R.id.position_one)).setText(mText);
return root;
}
}
my fragment two:
public class ScreenTwo extends Fragment {
private String mText;
public static ScreenTwo newInstance(String text) {
ScreenTwo f = new ScreenTwo(text);
return f;
}
public ScreenTwo() {
}
public ScreenTwo(String text) {
this.mText = text;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.screen_two, container, false);
((TextView) root.findViewById(R.id.position_two)).setText(mText);
return root;
}
}
Thanks & Regards,
Aditya. J

Just override this method in FragmentpagerAdapter:
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(ViewGroup container, int position, Object object);
}
And remove:
super.destroyItem(ViewGroup container, int position, Object object);