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How to update UI elements from a background thread in Android?

Ask Time:2019-03-15T23:10:30         Author:Amine

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I implemented a custom Android camera using the camera2 api and when I click capture button I save the captured image to my phone eternal storage.

Now I needed to show a popup to enter the picture name before saving it and this popup has an imageView to show the captured image.

Even though I am loading the image from the Main thread I am getting this error

  "Only the original thread that created a view hierarchy can touch its views"

Here is the code

  private void initPopup(final Bitmap bitmap) {

    popAddName = new Dialog(this);
    popAddName.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
    popAddName.getWindow().setLayout(Toolbar.LayoutParams.MATCH_PARENT, Toolbar.LayoutParams.WRAP_CONTENT);
    popAddName.getWindow().getAttributes().gravity = Gravity.TOP;

    popup_add = popAddName.findViewById(R.id.popup_add);
    popup_img = popAddName.findViewById(R.id.popup_img);
    popup_name = popAddName.findViewById(R.id.popup_name);

    Thread thread = new Thread() {
        public void run() {
            runOnUiThread(new Runnable() {
                public void run() {
                    Picasso.with(getApplicationContext()).load(getImageUri(getApplicationContext(), bitmap)).placeholder(R.drawable.placeholder).into(popup_img);


Here is the method to convert Bitmap to Uri for Picasso loading

  public Uri getImageUri(Context inContext, Bitmap inImage) {
    ByteArrayOutputStream bytes = new ByteArrayOutputStream();
    inImage.compress(Bitmap.CompressFormat.JPEG, 100, bytes);
    String path = MediaStore.Images.Media.insertImage(inContext.getContentResolver(), inImage, "Title", null);
    return Uri.parse(path);

This is the capture method

    ImageReader.OnImageAvailableListener readerListener = new ImageReader.OnImageAvailableListener() {
            public void onImageAvailable(ImageReader imageReader) {
                Image image = null;
                try {
                    image = reader.acquireLatestImage();
                    ByteBuffer buffer = image.getPlanes()[0].getBuffer();
                    byte[] bytes = new byte[buffer.capacity()];
                    //CONVERTION BYTES[] TO BITMAP
                    Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);

                    //create a new folder in external storage directory
                    String lorealFolder = "coffretPics";
                    File f = new File(Environment.getExternalStorageDirectory(), lorealFolder);
                    if (!f.exists()) {


                    file = new File(Environment.getExternalStorageDirectory() + "/" + lorealFolder + "/" + UUID.randomUUID().toString() + ".jpg");


                } catch (FileNotFoundException e) {
                } catch (IOException e) {
                } finally {
                        if (image != null)

            private void save(byte[] bytes) throws IOException {
               /* OutputStream outputStream = null;
                try {
                    outputStream = new FileOutputStream(file);
                } finally {
                    if (outputStream != null) {

Can someone please tell me what's the problem ?

Author:Amine,eproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article:https://stackoverflow.com/questions/55185583/how-to-update-ui-elements-from-a-background-thread-in-android