AsyncTaskReferenceLeakActivity.java

public class AsyncTaskReferenceLeakActivity extends AppCompatActivity {

    private TextView textView;
    private BackgroundTask backgroundTask;

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

        /*
         * Executing AsyncTask here!
         * */
        backgroundTask = new BackgroundTask(textView);
        backgroundTask.execute();
    }


    /*
     * Fix number 1
     * */
    private static class BackgroundTask extends AsyncTask<Void, Void, String> {

        private final WeakReference<TextView> messageViewReference;
        private BackgroundTask(TextView textView) {
            this.messageViewReference = new WeakReference<>(textView);
        }


        @Override
        protected String doInBackground(Void... voids) {

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "The task is completed!";
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
          /*
           * Fix number 3
           * */          
            TextView textView = messageViewReference.get();
            if(textView != null) {
                textView.setText(s);
            }
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        /*
         * Fix number 2
         * */
        if(backgroundTask != null) {
            backgroundTask.cancel(true);
        }
    }
}