public void setChecked(boolean check) {
		invalidate();
		this.check = check;
		setPressed(false);
		changeBackgroundColor(getResources().getColor(
				android.R.color.transparent));
		if (check) {
			step = 0;
		}
		if (check)
			checkView.changeBackground();

	}
Make a dark color to press effect

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