@Override
		protected void onDraw(Canvas canvas) {
			super.onDraw(canvas);

			if (check) {
				if (step < 11){
					step++;
					invalidate();
				}
			} else {
				if (step >= 0){
					step--;
					invalidate();
				}
				if (step == -1){
					invalidate();
					changeBackground();
				}
			}
			Rect src = new Rect(40 * step, 0, (40 * step) + 40, 40);
			Rect dst = new Rect(0, 0, this.getWidth() - 2, this.getHeight());
			canvas.drawBitmap(sprite, src, dst, null);

		}
Make a dark color to press effect

@return
MaterialDesignLibrary/MaterialDesign/src/main/java/com/gc/materialdesign/views/CheckBox.java