Update recyclerView Adapter on return to previous activity with newly created item

Question

I'm working on an App to manage my workouts based on a room database.

Here I have a recyclerview with adapter for exercises in a workout. My current problem is that new exercises are not shown in the recyclerview after creating them and switching back to the workout-activity.

It seems like a quite easy topic (update recyclerview after returning from other activity) but I cant' get it working.

• initial load of exercises at onCreate of workout-Activity:

   class GetExercises extends AsyncTask<Long, Void, List<Exercise>>{ @Override protected List<Exercise> doInBackground(Long... params){ if (params.length == 0 || params.length > 1) return null; return DatabaseClient.getInstance(getApplicationContext()).getAppDatabase().exerciseDao().getReferenced(params[0]); } protected void onPostExecute(List<Exercise> exerciseList){ super.onPostExecute(exerciseList); rv_exercises.setAdapter(new Adapter_Exercise_RV(Activity_Workout_Edit.this, exerciseList)); } }

• creating a new exercise and returning the id to previous workout-activity:

   class CreateExercise extends AsyncTask<Void, Void, Void> { long id; @Override protected Void doInBackground(Void... voids) { Exercise ex = new Exercise(); ex.setTitle(sTitle); ex.setSet(sSet); ex.setRep(sRep); ex.setAsTimer(bAsTimer); ex.setWorkoutId(workoutId); id = DatabaseClient.getInstance(getApplicationContext()).getAppDatabase().exerciseDao().insertwithRet(ex); return null; } @Override protected void onPostExecute(Void aVoid) { super.onPostExecute(aVoid); finish(id); Toast.makeText(getApplicationContext(), "created new exercise", Toast.LENGTH_LONG).show(); } } new CreateExercise().execute();

• update adapter onActivityResult at workout-activity

   protected void onActivityResult(int requestCode, int resultCode, Intent data){ super.onActivityResult(requestCode, resultCode, data); if(requestCode == 1 && resultCode == RESULT_OK){ long exerciseId = (long) data.getExtras().get("exerciseId"); rv_exercises.getAdapter().notifyDataSetChanged(); } }

the exercise is created in the database, and after reopening the workout the new exercise is shown correctly. I do have a feeling that "notifyDataSetChanged" is not working, but can't find why?

Answer 1

The issue is that, in the next activity you are inserting an item to db, and returning its id but in onActivityResult , you do not add the item to the adapter, what you need to do is to fetch the item inserted to the DB, using the exerciseId , and then you add that item to the adapter and then you call to notify the adapter.

protected void onActivityResult(int requestCode, int resultCode, Intent data){
  super.onActivityResult(requestCode, resultCode, data);
  if(requestCode == 1 && resultCode == RESULT_OK){
      long exerciseId = (long) data.getExtras().get("exerciseId");
      GetExerciseById(exerciseId).execute();
  }
}

Task to get the inserted entity

class GetExerciseById extends AsyncTask<Long, Void, Exercise>{

     long exerciseId=0;
     GetExerciseById(long exerciseId){
       this.exerciseId=exerciseId;
     }

      @Override
      protected Exercise doInBackground(Long... params){
          if (this.exerciseId == 0) return null;
          return DatabaseClient
                  .getInstance(getApplicationContext())
                  .getAppDatabase().exerciseDao()
                  .getExcerciseById(exerciseId);
      }

      protected void onPostExecute(Exercise exercise){
          super.onPostExecute(exerciseList);
          if(exercise==null) return;//no item found with given id;
          if(rv_exercises.getAdapter() instanceof Adapter_Exercise_RV )
          {
             Adapter_Exercise_RV adapter = (Adapter_Exercise_RV )rv_exercises.getAdapter();
             adapter.addItem(exercise);
         }
      }
  }

In your Adapter_Exercise_RV class

void addItem(Exercise exercise){
  yourDatalist.add(exercise);
  notifyItemInserted(yourDatalist.size()-1);
}

In your DAO

@Query("SELECT * FROM exercises WHERE workoutId:=exerciseId")//relative names and ids
Exercise getExcerciseById(long exerciseId)