Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference android studio

Question

I am trying to build an app with android studio. I am following a tutorial but the thing is, the guy paused the screen to start the emulator and when he played it again a piece of code was missing. I don't know for sure what he did but I tried all of the options presented to me.

I am getting this error: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference

code:

public void onResponse(Call<Users> call, Response<Users> response) {
    if (response.isSuccessful()) {
        mediaObjectList = (ArrayList<MediaObject>) response.body().getAllPosts();
        recyclerview.setMediaObjects(mediaObjectList);
        
        VideoPlayerRecyclerAdapter adapter = new VideoPlayerRecyclerAdapter(mediaObjectList, initGlide());
        recyclerview.setAdapter(adapter);
        adapter.notifyDataSetChanged();
        recyclerview.setKeepScreenOn(true);
        recyclerview.smoothScrollToPosition(mediaObjectList.size()+1);
    
    } else {
        Toast.makeText(HomeActivity.this, "Network Error.", Toast.LENGTH_SHORT).show();
    }
}

I'm getting the error on this line:

recyclerview.smoothScrollToPosition(mediaObjectList.size()+1);

score 1 · Accepted Answer · answered Sep 06 '20 at 18:41

Check if getAllPost() has value or not

Correct Way:

public void onResponse(Call<Users> call, Response<Users> response) {
            if (response.isSuccessful()) {
                mediaObjectList = (ArrayList<MediaObject>) response . body ().getAllPosts();
                if (mediaObjectList != null) {
                    recyclerview.setMediaObjects(mediaObjectList);
                    VideoPlayerRecyclerAdapter adapter = new VideoPlayerRecyclerAdapter(mediaObjectList, initGlide());
                    recyclerview.setAdapter(adapter);
                    adapter.notifyDataSetChanged();
                    recyclerview.setKeepScreenOn(true);
                    recyclerview.smoothScrollToPosition(mediaObjectList.size() + 1);
                } else {
                    Toast.makeText(HomeActivity.this, "No Post Available.", Toast.LENGTH_SHORT).show();
                }
            }
            else {
                Toast.makeText(HomeActivity.this, "Network Error.", Toast.LENGTH_SHORT).show();
            }
        }

This means that `response.body().getAllPosts()` is returning null and you must check the method body — Ela Łabaj, Sep 06 '20 at 18:54

Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference android studio

1 Answers1