HandlerLeakExample.java

public class MainActivity extends AppCompatActivity {
    private static final String IMAGE_URL = "https://www.android.com/static/img/android.png";

    private static final int MSG_SHOW_PROGRESS = 1;
    private static final int MSG_SHOW_IMAGE = 2;

    private ProgressBar progressIndicator;
    private ImageView imageView;
    private Handler handler;

    class ImageFetcher implements Runnable {
        final String imageUrl;

        ImageFetcher(String imageUrl) {
            this.imageUrl = imageUrl;
        }

        @Override
        public void run() {
            handler.obtainMessage(MSG_SHOW_PROGRESS).sendToTarget();
            InputStream is = null;
            try {
                // Download image over the network
                URL url = new URL(imageUrl);
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();

                conn.setRequestMethod("GET");
                conn.setDoInput(true);
                conn.connect();
                is = conn.getInputStream();

                // Decode the byte payload into a bitmap
                final Bitmap bitmap = BitmapFactory.decodeStream(is);
                handler.obtainMessage(MSG_SHOW_IMAGE, bitmap).sendToTarget();
            } catch (IOException ignore) {
            } finally {
                if (is != null) {
                    try {
                        is.close();
                    } catch (IOException ignore) {
                    }
                }
            }
        }
    }

    class UIHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_SHOW_PROGRESS: {
                    imageView.setVisibility(View.GONE);
                    progressIndicator.setVisibility(View.VISIBLE);
                    break;
                }
                case MSG_SHOW_IMAGE: {
                    progressIndicator.setVisibility(View.GONE);
                    imageView.setVisibility(View.VISIBLE);
                    imageView.setImageBitmap((Bitmap) msg.obj);
                    break;
                }
            }
        }
    }

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

        progressIndicator = (ProgressBar) findViewById(R.id.progress);
        imageView = (ImageView) findViewById(R.id.image);

        handler = new UIHandler();

        final Thread workerThread = new Thread(new ImageFetcher(IMAGE_URL));
        workerThread.start();
    }
}