Stopping Exoplayer onSwipe of ViewPager

Question

I am using a ViewPager with single fragment instance in which I am showing Media files like Images, Videos, Audio.

I have implemented ExoPlayer for handling Video & Audio files. And Glide for images.

To avoid the memory leaks I am releasing the ExoPlayer object like this in ItemViewerFragment.java :

 private void releasePlayer() {
        if (player != null) {
            player.release();
            player = null;
            trackSelector = null;
            simpleExoPlayerView.setPlayer(null);
        }
    }

    @Override
    public void onStart() {
        super.onStart();
        if (player == null && currentGalleryModel != null) {
            initializePlayer();
        }
    }

    @Override
    public void onResume() {
        super.onResume();
        if (player == null && currentGalleryModel != null) {
            initializePlayer();
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        releasePlayer();
    }

    @Override
    public void onStop() {
        super.onStop();
        releasePlayer();
    }

And in onViewCreated() I am initializing view like this :

 @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        if (currentGalleryModel.isVideo() || currentGalleryModel.isAudio()) {

            simpleExoPlayerView.setVisibility(View.VISIBLE);
            imageView.setVisibility(View.GONE);

            initializePlayer();
        } else if (currentGalleryModel.isImage() || currentGalleryModel.isGif()) {
            simpleExoPlayerView.setVisibility(View.GONE);
            imageView.setVisibility(View.VISIBLE);


            Glide.with(this)
                    .load(currentGalleryModel.getFilePath())
                    .placeholder(android.R.color.black)
                    .fitCenter()
                    .diskCacheStrategy(DiskCacheStrategy.NONE)
                    .into(imageView);

        }
    }

I am using FragmentStatePagerAdapeter. This is the getItem method :

@Override
public Fragment getItem(int position) {
    return ItemViewerFragment.newInstance(mItems.get(position));
}

I am not able to detect the onPause of the fragment on first swipe of Viewpager. On second swipe video/audio files are stopped playing.

In activity I have tried adding .addOnPageChangeListener :

@Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

     try {
        ((ItemViewerFragment)mAdapter.getItem(mPreviousPos)).imHiddenNow();
        } catch (Exception e) {
            e.printStackTrace();
        }
        mPreviousPos = position;
    }

And in ItemViewerFragment.java :

public void imHiddenNow(){
      releasePlayer();
    }

Still video/audio keeps on playing.

Here is a Video Link to the Screencast.

Demo project GitHub link.

Answer 1

I followed an approach of maintaining HashMap of fragment objects inside PagerAdapter

1. Declare an interface :

interface FragmentLifecycle {
    void onPauseFragment()
}

2. Implement an interface in Fragment.

public void onPauseFragment() {
    if (simpleExoPlayer != null){
        simpleExoPlayer.setPlayWhenReady(false);
    }
}

3. Store all the fragment objects in a HashMap<Integer,Fragment> with there respective positions as a key. Declare hashmap inside PagerAdapter. Also declare one getter method for accessing fragment objects from hashmap. e.g.

   @Override
   public Fragment getItem(int position) {
       ItemViewerFragment fragment = ItemViewerFragment.newInstance(mItems.get(position));
       mFragments.put(position,fragment);
       return fragment;
   }
   

   public ItemViewerFragment getMapItem(int position) { return mFragments.get(position); }

4. In activity where you have declared viewPager keep one variable currentPosition and implement ViewPager.OnPageChangeListener.

5. Inside onPageSelected method,

       @Override
       public void onPageSelected(int position) {
           if(mAdapter.getMapItem(currentPosition) != null) (mAdapter.getMapItem(currentPosition)).onPauseFragment();
           currentPosition = position;
       }
   

Answer 2

Edit from the future: you should never hold a reference to Fragment instances directly inside a FragmentPagerAdapter, because it can cause crashes after process death.

Here is the code for the pager adapter:

 class ViewPagerAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
    }
}

Here is the scroll Listener:

  viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
          //Stop media here.
        }

        @Override
        public void onPageSelected(int position) {
          //Save your previous position here.
        }

        @Override
        public void onPageScrollStateChanged(int state) {
         
        }
    });

For the media you can use a for Loop and add all the fragments to the list at once and then use this for efficiency :

viewPager.setOffscreenPageLimit(3);

This will make sure only 3 instances of your fragment are available which is enough.

For using single fragment i would suggest you to do it like this:

 public MyFragment() {

}

//This is to send a file to the fragment if you need it.
public static MyFragment newInstance(File file) {
    MyFragment fragment = new MyFragment();
    Bundle bundle = new Bundle();
    bundle.putSerializable("file", file);
    fragment.setArguments(bundle);
    return fragment;
}

Then in the onCreate of Fragment you can retrieve your file like this:

File file;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    file = getArguments().getSerializable("file");
   
}

Now add your fragments to pager like this:

 for (int i = 0; i < totalFiles; i++) {
            viewPagerAdapter.addFragment(MyFragment.newInstance(fileList.get(i));
        }

Hope this helps.

Answer 3

It's been more then a year since I used Exoplayer & I kinda tackled a similar problem. Please note that the APIs have changed a little bit so take the following code just to get an idea on how to implement a potential solution. Please let me know if it doesn't work, I'll look into the APIs further and get back to you.

Coming to the solution:

private int mPlayerCurrentPosition;

private int getCurrentPlayerPosition() {
     return mExoPlayer.getCurrentPosition();
}

// call this from onPause
private void releaseExoplayer() {
     mPlayerCurrentPosition = getPlayerCurrentPosition();
     mExoPlayer.setPlayWhenReady(false);
     mExoPlayer.release(); // this will make the player object eligible for GC
}

private void resumePlaybackFromPreviousPosition(int prevPosition) {
    mExoPlayer.seekTo(mPlayerCurrentPosition );
}

Answer 4

The problem is that onPause and onResume are not called when the fragment visibility changed in ViewPager. The solution is to add 2 visibility events: losingVisibility and gainVisibility.

Why is it a great solution?

Because you keep the framework managing Fragment cache and lifecycle. We just add the callbacks needed to pause and resume our media in our fragment.

Step-by-step:

The below code is just an explanation for my code. Check Step*.java classes to see full implementation.

1. Create losingVisibility and gainVisibility methods in YourFragment.java:

   public class YourFragment extends Fragment {
   
       /**
         * This method is only used by viewpager because the viewpager doesn't call onPause after
         * changing the fragment
         */
       public void losingVisibility() {
           // IMPLEMENT YOUR PAUSE CODE HERE
           savePlayerState();
           releasePlayer();
       }
   
       /**
         * This method is only used by viewpager because the viewpager doesn't call onPause after
         * changing the fragment
       */
       public void gainVisibility() {
           // IMPLEMENT YOUR RESUME CODE HERE
           loadVideo();
       }
   }
   

2. Call losingVisibility and gainVisibility every time a new page is selected (onPageSelected) in YourActivity.java:

   mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
       @Override
       public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
       }
   
       @Override
       public void onPageSelected(int position) {
           YourFragment cachedFragmentLeaving = mYourPagerAdapter.getCachedItem(mCurrentItem);
           if (cachedFragmentLeaving != null) {
               cachedFragmentLeaving.losingVisibility();
           }
           mCurrentItem = position;
           YourFragment cachedFragmentEntering = mYourPagerAdapter.getCachedItem(mCurrentItem);
           if (cachedFragmentEntering != null) {
               cachedFragmentEntering.gainVisibility();
           }
       }
   
       @Override
       public void onPageScrollStateChanged(int state) {
       }
   });
   

3. Add getCachedItem to YourPagerAdapter.java:

The 3rd step is adding a method to retrieve cached fragments. To do it we must cache a reference to a fragment created (overriding instantiateItem) and release the same reference (overriding destroyItem).

    public class YourPagerAdapter extends FragmentStatePagerAdapter {

            private SparseArray<YourFragment> mFragmentsHolded = new SparseArray<>();


        @NonNull
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            Object fragment = super.instantiateItem(container, position);
            if(fragment instanceof StepFragment) {
                mFragmentsHolded.append(position, (StepFragment) fragment);
            }
            return fragment;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            mFragmentsHolded.delete(position);
            super.destroyItem(container, position, object);
        }

        public YourFragment getCachedItem(int position) {
            return mFragmentsHolded.get(position, null);
        }
    }