ANDROID: How to fix the position of a ImageButton relative to the background?

How to fix the position/layout of a ImageButton/Button/ImageView relative to the background?

I'd tried something like this:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/background_img"
>

<ImageButton
    android:id="@+id/btn1"
    android:layout_width="开发者_运维技巧52dip"
    android:layout_height="52dip"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="87dip"        
    android:background="@drawable/btn1"
/>    
</RelativeLayout> 

When I change the display resolution, the background_img stretch to cover the new area, but the ImageButton doesn't streetch and doesn't respect the bottom margin proportionately.

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It's because you hardcoded the height and with. Set them to fill_parent and it will then fit the margin.