Question

My question has to do with applying an image overlay to all button pressed events. So, for example, in Android 4.0 and higher with the holo setup, when you press any button, it has the light blue overlay on the button. In the earlier version of android, it is orange. I know how to setup the button to change the image for pressed, focused, and default in the XML with the selector and item tags, but that would require me to make another image of my button but with a light blue overlay which means i know have 2 pictures for every button. My app is going to have a lot of buttons, and i’d like to keep the file size of the app as small as possible.

So the point of the question is, is there a way to make just 1 picture (the light blue 25% opacity image) apply as an overlay to all button presses while also keeping the original background of the button I had set stay there?

Answer 1

Load in the image. Then draw the alpha color ontop of it.

Then use the modified image to set the button Image.

Bitmap img = BitmapFactory.decodeFile(pathName); // or decodeResource  etc....

Canvas canvas = new Canvas(img);
Paint alphaPaint = new Paint();

// Color to apply.
alphaPaint.setColor(Color.BLUE);
alphaPaint.setAlpha(20);

// Draw rectangle over your image using the alpha colored paint.
canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), alphaPaint);
myButton.setImageBitmap(img );