How to prevent onClick method on transparent portion of a PNG-loaded ImageView

android, imageview, onclick

Solution

This one sample makes ImageView's transparent area not clickable.

ImageView:

ImageView imgView= (ImageView) findViewById(R.id.color_blue);
imgView.setDrawingCacheEnabled(true);
imgView.setOnTouchListener(changeColorListener);

OnTouchListener:

private final OnTouchListener changeColorListener = new OnTouchListener() {

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        Bitmap bmp = Bitmap.createBitmap(v.getDrawingCache());
        int color = bmp.getPixel((int) event.getX(), (int) event.getY());
        if (color == Color.TRANSPARENT)
            return false;
        else {
            //code to execute
            return true;
        }
    }
};

Problem

I am currently developing an Android app that displays multiple images (as `ImageView's`) stacked on top of each other. Here is how the layers are currently configured: - Background layer: scales the entire screen, must be clickable - Foreground layer: scales the entire screen, must be clickable, contains transparency which allows the user to see some of the background layer The problem I face is with the foreground layer. I am assigning the `onClick()` method to the imageview, but the method is being called whether they hit the portion of the image which is visible as well as the part which contains transparency. I only want the foreground ImageView `onClick()` method to be called when the user clicks a portion of that imageview that is not transparent. This is what the scenario looks like: The diagonal lines represent the transparent portion of the Foreground image. If a user touches this space, I want it to access the Background image instead of the Foreground image. Thank you for any assistance you can provide. Here is the solution I implemented (Thanks to answer below): ``` //ontouchlistener - gets X and Y from event private void setClick(View view) { view.setOnTouchListener(new View.OnTouchListener() { public boolean onTouch(View v, MotionEvent event) { int imageId = getImageId((int)event.getX(), (int)event.getY()); if (imageId >= 0) performActions(imageId); return false; } }); } //get the ID of the first imageview (starting from foreground, //working backwards) which contains a non-transparent pixel private int getImageId(int x, int y) { ViewGroup parent = (ViewGroup) findViewById(R.id.relative_layout); for (int a = parent.getChildCount()-1; a >= 0; a--) { if (parent.getChildAt(a) instanceof ImageView) if (!checkPixelTransparent((ImageView)parent.getChildAt(a), x, y)) return parent.getChildAt(a).getId(); } return -1; } //get bitmap from imageview, get pixel from x, y coord //check if pixel is transparent private boolean checkPixelTransparent(ImageView iv, int x, int y) { Bitmap bitmap = ((BitmapDrawable) iv.getDrawable()).getBitmap(); if (Color.alpha(bitmap.getPixel(x, y)) == 0) return true; else return false; } ```

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