NullPointerException with android AsyncTask and RecyclerView

Question

I have an AsyncTask class to download image from web and set it into in ImageView (referred from here)

Relevant Activity code:

    public class ListAdoptions extends AppCompatActivity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_list_adoptions);

            recyclerView = (RecyclerView) findViewById(R.id.recycler_view);

            mAdapter = new PetsAdapter(petList);
            RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
            recyclerView.setLayoutManager(mLayoutManager);
            recyclerView.setItemAnimator(new DefaultItemAnimator());
            recyclerView.setAdapter(mAdapter);

            preparePetData();
        }


        private void preparePetData() {

            DownloadImageTask imgtask = new DownloadImageTask((ImageView) findViewById(R.id.picture));
            imgtask.execute("https://i.ytimg.com/vi/opKg3fyqWt4/hqdefault.jpg");

            mAdapter.notifyDataSetChanged();
        }

        private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
            ImageView bmImage;

            public DownloadImageTask(ImageView bmImage) {
                this.bmImage = bmImage;
            }

            protected Bitmap doInBackground(String... urls) {
                String urldisplay = urls[0];
                Bitmap mIcon11 = null;
                try {
                    InputStream in = new java.net.URL(urldisplay).openStream();
                    mIcon11 = BitmapFactory.decodeStream(in);
                } catch (Exception e) {
                    Log.e("Error", e.getMessage());
                    e.printStackTrace();
                }
                return mIcon11;
            }

            protected void onPostExecute(Bitmap result) {
                bmImage.setImageBitmap(result);
            }
        }
    }

Error:

Process: com.example.test3, PID: 8427
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference
        at com.example.petadoption.ListAdoptions$DownloadImageTask.onPostExecute(ListAdoptions.java:171)
        at com.example.petadoption.ListAdoptions$DownloadImageTask.onPostExecute(ListAdoptions.java:150)
        at android.os.AsyncTask.finish(AsyncTask.java:695)
        at android.os.AsyncTask.-wrap1(Unknown Source:0)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

Yeah, I am quite new to JAVA and android (One day old) so please dont judge x( — MohitC, Oct 14 '19 at 21:53
Strongly recommend you use a standard image loading library, such as [Glide](https://github.com/bumptech/glide/blob/master/README.md) or [Coil](https://github.com/coil-kt/coil/blob/master/README.md) — charles-allen, Oct 14 '19 at 21:57
@AjahnCharles I got same error with glide "argument must not be null" — MohitC, Oct 14 '19 at 22:17
I meant replace the AsyncTask entirely. You should call Glide from the RV Adapter/ViewHolder. — charles-allen, Oct 14 '19 at 22:27
Then you're not getting your ImageView correctly... (but that should be far easier to fix without the AsyncTask) — charles-allen, Oct 14 '19 at 22:28

score 1 · Answer 1 · answered Oct 14 '19 at 22:00

1

Can''t see the whole code but message is null object... Make sure you defined bmImage in ListAdoptions like findViewById(R.id.bmImage) and check if this object exist in xml with id bmImage

answered Oct 14 '19 at 22:00

Adnan Ahmetgil

11
2

bmimage is local variable to asynctask – MohitC Oct 14 '19 at 22:17

score 1 · Answer 2 · answered Oct 14 '19 at 22:01

1

Things to do when dealing with null:

make sure you spelled the name right
add if statements to see when things are becoming null
use the debugger and step through your code to see why the object is null

For some reason bmImage doesn't exist and i would recommend looking in your layouts and this class itself to find the null

answered Oct 14 '19 at 22:01

Evan

17
5

bmImage is a local variable to asynctask – MohitC Oct 14 '19 at 22:06

Alexandr Ukolov · Accepted Answer · 2019-10-14T22:57:43.900

1

It looks like your bmImage is always null. Most likely findViewById(R.id.picture) always null. Make sure that you defined ImageView with id "picture" and didn't miss at with plus in your XML layout file. android:id="@+id/picture"

edited Oct 14 '19 at 22:57

answered Oct 14 '19 at 22:47

Alexandr Ukolov

126
5

NullPointerException with android AsyncTask and RecyclerView

3 Answers3