Stop Handler when Fragment is destroyed

Question

I am starting handler in a fragment like below :

    public class FeedsFragment extends Fragment{
           private Handler handler;
           private Runnable runnableCode;

           @Override
           public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
// Create the Handler object (on the main thread by default)
        handler = new Handler();

        // Define the task to be run here
        runnableCode = new Runnable() {
            @Override
            public void run() {

                    // Get the No of New Feeds
                    getFeedCounts();

                    // Repeat this runnable code again every 30 seconds
                    handler.postDelayed(runnableCode, 30,000);
            }
        };

        handler.post(runnableCode);
}

@Override
    public void onDetach() {
        super.onDetach();
        handler.removeCallbacksAndMessages(runnableCode);

    }

@Override
    public void onDestroyView() {
        handler.removeCallbacksAndMessages(runnableCode);
        super.onDestroyView();
    }

@Override
    public void onPause() {
        super.onPause();
        handler.removeCallbacksAndMessages(runnableCode);
    }

 @Override
    public void onResume() {

        /**
         * Start the handler again if coming back from any profile page
         * or hashtag search
         */ 
            isHandlerStopped = false;
            handler.post(runnableCode);
        super.onResume();
    }

I am removing all callbacks in onDetach and onDestroyView functions, but it is not working.

When I load a different fragment in the same activity this handler doesn't stop itself, handler stops only when I load some other activity in my application.

I want this handler to run only when the fragment in which I am using it is loaded in the activity, if some other fragment is being loaded in the same activity it should be stopped.

Also, this fragment is inside viewpager, so when I switch the tab and other fragment gets loaded the handler doesn't stop. Please check the below code in activity :

ViewPager pager = (ViewPager) findViewById(R.id.viewpager);
FeedsFragment feedsFragment;
pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                // when user do a swipe the selected tab change
                switch (position){
                    case 0:
                        break;
                    case 1:
                        feedsFragment.removeHandler();
                        break;
                    case 2:
                        feedsFragment.removeHandler();
                        break;
                    case 3:
                        feedsFragment.removeHandler();
                        break;

                }

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

FragmentAdapter adapter = new FragmentAdapter(getActivity().getSupportFragmentManager());

feedsFragment = FeedsFragment.newInstance(bundle);
                adapter.addFragmentWithIcon(FeedsFragment.newInstance(null))
                        , mContext.getResources().getString(R.string.feed_tab_name));
                adapter.addFragmentWithIcon(FeedFriendRequests.newInstance(null),
                        mContext.getResources().getString(R.string.requests_tab_name));
                adapter.addFragmentWithIcon(NewMessagesFragment.newInstance(null), mContext.getResources().getString(R.string.message_tab_name));
                adapter.addFragmentWithIcon(NotificationFragment.newInstance(null)
                        , mContext.getResources().getString(R.string.notification_tab_name));

pager.setAdapter(adapter);

When I select any other tab at that time I'm calling the method removeHandler in FeedFragment.

public void removeHandler(){
        handler.removeCallbacks(runnableCode);
    }

But still handler is getting called.

Please help me if anyone have idea about this.

Thanks a lot in advance

Answer 1

I don't think it has to do with your fragment lifecycle. You need to replace

handler.removeCallbacksAndMessages(runnableCode);
// this does not seem to work

with

handler.removeCallbacks(runnableCode);

Just an alternative create a method in FeedsFragment

public void removeHandler()
{
    Log.i("Stop Handler ","Yes");
    handler.removeCallbacks(runnableCode);
}

In activity when you want to replace fragment

if(feedsFragment.isAdded())
{
     feedsFragment.removeHandler();
}
...// rest of the code to replace the fragment with new one

Edit:

viewPager.addOnPageChangeListener(pageChangeListener);
    viewPager.post(new Runnable() {
        @Override
        public void run() {
            pageChangeListener.onPageSelected(0);
        }
    });

Then

    ViewPager.OnPageChangeListener pageChangeListener = new ViewPager.OnPageChangeListener() {

    int currentPosition = 0;

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


    }

    @Override
    public void onPageSelected(int newPosition) {


        FragmentLifeCycle fragmentToShow = (FragmentLifeCycle) adapter.getItem(newPosition);
        fragmentToShow.onResumeFragment();

        if(newPosition==0)
        {
            currentPosition = newPosition;
        }else {
            FragmentLifeCycle fragmentToHide = (FragmentLifeCycle) adapter.getItem(currentPosition);
            fragmentToHide.onPauseFragment();

            currentPosition = newPosition;
        }
}

Have a interface

 public interface FragmentLifeCycle {

 void onPauseFragment();
 void onResumeFragment();

 }

Implement the interface in all fragments. Assuming the handler is used in Fragment at position 0.

@Override
public void onPauseFragment() {

    if(handler!=null)
    handler.removeCallbacks(runnableCode);
}

@Override
public void onResumeFragment() {
    handler = new Handler();

    // Define the task to be run here
    runnableCode = new Runnable() {
        @Override
        public void run() {

            Log.i("Do ","Something");
            handler.postDelayed(runnableCode, 3000);
        }
    };

    handler.post(runnableCode);
}

In other fragment just implement the interface and do nothing.