Can't update RecyclerView from my model Class?

Question

I am working on a RecyclerView which must be Draggable & swipeable. Everything works perfect.

The Data is getting Fetched in one class called ExerciseDataProvider & the RV code is another Fragment RecyclerListViewFragment.

The problem is that i can't notify Data changed from the FetchExercise on postExecute method. So the Data's are not getting populated in the RV.

Please Guide me in a Right Direction.

ACTIVITY

    public class DraggableSwipeableExampleActivity extends AppCompatActivity {
        private static final String FRAGMENT_TAG_DATA_PROVIDER = "data provider";
        private static final String FRAGMENT_LIST_VIEW = "list view";
        private static final String FRAGMENT_TAG_ITEM_PINNED_DIALOG = "item pinned dialog";

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_demo);

            if (savedInstanceState == null) {
                getSupportFragmentManager().beginTransaction()
                        .add(new ExampleDataProviderFragment(), FRAGMENT_TAG_DATA_PROVIDER)
                        .commit();
                getSupportFragmentManager().beginTransaction()
                        .add(R.id.container, new RecyclerListViewFragment(), FRAGMENT_LIST_VIEW)
                        .commit();
            }
        }

 public AbstractDataProvider getDataProvider() {
        final Fragment fragment = getSupportFragmentManager().findFragmentByTag(FRAGMENT_TAG_DATA_PROVIDER);
        return ((ExampleDataProviderFragment) fragment).getDataProvider();
    }

DATA PROVIDER

public class ExerciseDataProvider extends AbstractDataProvider {
    private List<ConcreteData> mData;
    private ConcreteData mLastRemovedData;
    private int mLastRemovedPosition = -1;

    public ExerciseDataProvider() {
        new FetchExercise().execute();
        mData = new LinkedList<>();
    }

    class FetchExercise extends AsyncTask<Void,Void,Void> {

        @Override
        protected Void doInBackground(Void... params) {
            final int viewType = 0;
            final int swipeReaction = RecyclerViewSwipeManager.REACTION_CAN_SWIPE_UP | RecyclerViewSwipeManager.REACTION_CAN_SWIPE_DOWN;

            String url = "https://gist.githubusercontent.com/fake/cb9aa5494e7ee36ac3ca/raw/a4abfd19368063/exercise.JSON";
            Log.d("Path", url);
            try {
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder().url(url).build();
                Response response = client.newCall(request).execute();
                String jsonData = response.body().string();
                try {
                    JSONArray jsonArray = new JSONArray(jsonData);
                    for (int i = 0; i < jsonArray.length(); i++) {
                        final long id = i;
                        JSONObject jsonObject = jsonArray.getJSONObject(i);
                        String exercise_name = jsonObject.getString("name");
                        int exercise_duration = jsonObject.getInt("duration");

                        mData.add(new ConcreteData(id, viewType, exercise_name, exercise_duration, swipeReaction));
                        Log.d("exercise_name", exercise_name);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
        }
    }


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

    @Override
    public Data getItem(int index) {
        if (index < 0 || index >= getCount()) {
            throw new IndexOutOfBoundsException("index = " + index);
        }

        return mData.get(index);
    }

    @Override
    public int undoLastRemoval() {
        if (mLastRemovedData != null) {
            int insertedPosition;
            if (mLastRemovedPosition >= 0 && mLastRemovedPosition < mData.size()) {
                insertedPosition = mLastRemovedPosition;
            } else {
                insertedPosition = mData.size();
            }

            mData.add(insertedPosition, mLastRemovedData);

            mLastRemovedData = null;
            mLastRemovedPosition = -1;

            return insertedPosition;
        } else {
            return -1;
        }
    }

    @Override
    public void moveItem(int fromPosition, int toPosition) {
        if (fromPosition == toPosition) {
            return;
        }

        final ConcreteData item = mData.remove(fromPosition);
        mData.add(toPosition, item);
        mLastRemovedPosition = -1;
    }

    @Override
    public void removeItem(int position) {
        //noinspection UnnecessaryLocalVariable
        final ConcreteData removedItem = mData.remove(position);

        mLastRemovedData = removedItem;
        mLastRemovedPosition = position;
    }

    public static final class ConcreteData extends Data {

        private final long mId;
        private final String mText;
        private final int mViewType;
        private final int mDuration;
        private boolean mPinned;

        ConcreteData(long id, int viewType, String text, int duration, int swipeReaction) {
            mId = id;
            mViewType = viewType;
            mText = text;
            mDuration = duration;
        }

        @Override
        public int getViewType() {
            return mViewType;
        }

        @Override
        public int getDuration() {
            return mDuration;
        }

        @Override
        public long getId() {
            return mId;
        }

        @Override
        public String toString() {
            return mText;
        }

        @Override
        public String getText() {
            return mText;
        }

        @Override
        public boolean isPinned() {
            return mPinned;
        }

        @Override
        public void setPinned(boolean pinned) {
            mPinned = pinned;
        }

    }
}

RecyclerListViewFragment

public class RecyclerListViewFragment extends Fragment {
    private RecyclerView mRecyclerView;
    private RecyclerView.LayoutManager mLayoutManager;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.Adapter mWrappedAdapter;
    private RecyclerViewDragDropManager mRecyclerViewDragDropManager;
    private RecyclerViewSwipeManager mRecyclerViewSwipeManager;
    private RecyclerViewTouchActionGuardManager mRecyclerViewTouchActionGuardManager;

    public RecyclerListViewFragment() {
        super();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_recycler_list_view, container, false);
    }

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

        //noinspection ConstantConditions
        mRecyclerView = (RecyclerView) getView().findViewById(R.id.recycler_view);
        mLayoutManager = new LinearLayoutManager(getContext());

        // touch guard manager  (this class is required to suppress scrolling while swipe-dismiss animation is running)
        mRecyclerViewTouchActionGuardManager = new RecyclerViewTouchActionGuardManager();
        mRecyclerViewTouchActionGuardManager.setInterceptVerticalScrollingWhileAnimationRunning(true);
        mRecyclerViewTouchActionGuardManager.setEnabled(true);

        // drag & drop manager
        mRecyclerViewDragDropManager = new RecyclerViewDragDropManager();
        mRecyclerViewDragDropManager.setDraggingItemShadowDrawable(
                (NinePatchDrawable) ContextCompat.getDrawable(getContext(), R.drawable.material_shadow_z3));

        // swipe manager
        mRecyclerViewSwipeManager = new RecyclerViewSwipeManager();

        //adapter
        final MyDraggableSwipeableItemAdapter myItemAdapter = new MyDraggableSwipeableItemAdapter(getDataProvider());
        myItemAdapter.setEventListener(new MyDraggableSwipeableItemAdapter.EventListener() {
            @Override
            public void onItemRemoved(int position) {
                ((DraggableSwipeableExampleActivity) getActivity()).onItemRemoved(position);
            }

            @Override
            public void onItemViewClicked(View v, boolean pinned) {
                onItemViewClick(v, pinned);
            }
        });

        mAdapter = myItemAdapter;

        mWrappedAdapter = mRecyclerViewDragDropManager.createWrappedAdapter(myItemAdapter);      // wrap for dragging
        mWrappedAdapter = mRecyclerViewSwipeManager.createWrappedAdapter(mWrappedAdapter);      // wrap for swiping

        final GeneralItemAnimator animator = new SwipeDismissItemAnimator();
        animator.setSupportsChangeAnimations(false);

        mRecyclerView.setLayoutManager(mLayoutManager);
        mRecyclerView.setAdapter(mWrappedAdapter);  // requires *wrapped* adapter
        mRecyclerView.setItemAnimator(animator);

        // additional decorations
        //noinspection StatementWithEmptyBody
        if (supportsViewElevation()) {
            // Lollipop or later has native drop shadow feature. ItemShadowDecorator is not required.
        } else {
            mRecyclerView.addItemDecoration(new ItemShadowDecorator((NinePatchDrawable) ContextCompat.getDrawable(getContext(), R.drawable.material_shadow_z1)));
        }
        mRecyclerView.addItemDecoration(new SimpleListDividerDecorator(ContextCompat.getDrawable(getContext(), R.drawable.list_divider_h), true));
        mRecyclerViewTouchActionGuardManager.attachRecyclerView(mRecyclerView);
        mRecyclerViewSwipeManager.attachRecyclerView(mRecyclerView);
        mRecyclerViewDragDropManager.attachRecyclerView(mRecyclerView);
    }

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

    @Override
    public void onDestroyView() {
        if (mRecyclerViewDragDropManager != null) {
            mRecyclerViewDragDropManager.release();
            mRecyclerViewDragDropManager = null;
        }

        if (mRecyclerViewSwipeManager != null) {
            mRecyclerViewSwipeManager.release();
            mRecyclerViewSwipeManager = null;
        }

        if (mRecyclerViewTouchActionGuardManager != null) {
            mRecyclerViewTouchActionGuardManager.release();
            mRecyclerViewTouchActionGuardManager = null;
        }

        if (mRecyclerView != null) {
            mRecyclerView.setItemAnimator(null);
            mRecyclerView.setAdapter(null);
            mRecyclerView = null;
        }

        if (mWrappedAdapter != null) {
            WrapperAdapterUtils.releaseAll(mWrappedAdapter);
            mWrappedAdapter = null;
        }
        mAdapter = null;
        mLayoutManager = null;

        super.onDestroyView();
    }

    private void onItemViewClick(View v, boolean pinned) {
        int position = mRecyclerView.getChildAdapterPosition(v);
        if (position != RecyclerView.NO_POSITION) {
            ((DraggableSwipeableExampleActivity) getActivity()).onItemClicked(position);
        }
    }

    public AbstractDataProvider getDataProvider() {
        return ((DraggableSwipeableExampleActivity) getActivity()).getDataProvider();
    }

    public void notifyItemChanged(int position) {
        mAdapter.notifyItemChanged(position);
    }

    public void notifyItemInserted(int position) {
        mAdapter.notifyItemInserted(position);
        mRecyclerView.scrollToPosition(position);
    }
}

@VeereshCharantimath How can i set the Adapter in the OnPostExecute. Show me some Code. — Arulnadhan, Mar 12 '16 at 08:59

score 3 · Accepted Answer · edited May 23 '17 at 12:23

To update recyclerView from onPostExecute in a data provider class, your onPostExecute should have access to context where your recyclerView is defined.

Since your FetchExercise async task is defined inside ExerciseDataProvider class, try passing activity context to ExerciseDataProvider's constructor and then pass it on to FetchExercise async task as described here: getting context in AsyncTask

public class MyCustomTask extends AsyncTask<Void, Void, Long> {
    private Context mContext;
        public MyCustomTask (Context context){
           mContext = context;
        }
        protected void onPostExecute(Long result) {
           //use mContext to update recycler view
        }
    }
}

Use the context to update the recyclerView.

UPDATE

Step 1

Define an interface that will notify your activity of data set change inside a class that initialises your data provider class and pass activity context to constructor of data provider class.

public class ExampleDataProviderFragment extends Fragment {
    private AbstractDataProvider mDataProvider;

    //Define an interface that will notify your activity of data set change
    public interface EventListener {
        void onNotifyDataSetChanged();
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setRetainInstance(true); 

        //Pass activity context to ExerciseDataProvider
        mDataProvider = new ExerciseDataProvider(getActivity());
    }

    public AbstractDataProvider getDataProvider() {
        return mDataProvider;
    }
}

Step 2

Add context parameter to ExerciseDataProvider's constructor and use it to notify activity that implements your interface to notify dataset change.

public class ExerciseDataProvider extends AbstractDataProvider {
    private List<ConcreteData> mData;
    private ConcreteData mLastRemovedData;
    private int mLastRemovedPosition = -1;

    //Add context parameter to constructor
    public ExerciseDataProvider(Context context) {

        //Pass context to async task

        new FetchExercise(context).execute();
        mData = new LinkedList<>();
    }

    class FetchExercise extends AsyncTask<Void,Void,Integer> {
        Context mContext;

        public FetchExercise(Context context) {
            mContext = context;
        }

        @Override
        protected Integer doInBackground(Void... params) {
            ...
            return 1;
        }

        @Override
        protected void onPostExecute(Integer result) {
            super.onPostExecute(result);

            //Typecast context to interface defined above 
            //and notify dataset changes by calling its method

            ExampleDataProviderFragment.EventListener eventListener = (ExampleDataProviderFragment.EventListener)mContext;
            eventListener.onNotifyDataSetChanged();

        }
    }
}

Step 3

Implement above defined interface in your activity class and notify recyclerview adapter inside it

public class DraggableSwipeableExampleActivity extends AppCompatActivity 
    implements ExampleDataProviderFragment.EventListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
    }

    //implement interface method and notify recyclerview of changes
    @Override
    public void onNotifyDataSetChanged() {
        Fragment fragment = getSupportFragmentManager().findFragmentByTag(FRAGMENT_LIST_VIEW);

        // you might need to change visibility of `mWrappedAdapter` in the fragment that defines it or create a getter for it so that you can access it here
        ((RecyclerListViewFragment) fragment).mWrappedAdapter.notifyDataSetChanged(); 

    }
 ...
}

while passing the context i get a lot of errors. Can you just show it in my code please. — Arulnadhan, Mar 14 '16 at 15:45

score 0 · Answer 2 · answered Mar 14 '16 at 08:18

I think @random is correct you should be notifying your Recycle view on post execute.

@Override
protected void onPostExecute(Void aVoid) {
    mRecyclerViewAdapter.notifyDataSetChanged();
    super.onPostExecute(aVoid);
}

or if you have done something in your async task to add/delete something in the data set you would do:

@Override
protected void onPostExecute(Void aVoid) {
    mRecyclerViewAdapter.notifyItemRemoved(itemposition); // or item added
    mRecyclerViewAdapter.notifyDataSetChanged();
    super.onPostExecute(aVoid);
}

Hope it helps !

Can't update RecyclerView from my model Class?

2 Answers2