XML drawable composed of png and overlay

[moonlight]

I have a png button, which is enabled, non-pressed. When user click the button, I want only to darken the png. I need something like this:\[code\] <selector xmlns:android="http://schemas.android.com/apk/res/android" > //normal button with background my_button.png <item android:state_enabled="true" android:drawable="@drawable/my_button" //my_button.png /> //pressed button with background my_button.png overlayed by 50% black <item android:state_pressed="true" android:state_enabled="true" > <RelativeLayout android:layout_width="wrap_content" android:layout_height="wrap_content"> <bitmap android:src="http://stackoverflow.com/questions/14553784/@drawable/my_button"/> <color android:color="#00000088"/> </RelativeLayout> </item> </selector>\[/code\]Is there some way how to do that? Or do I must have another png file?