How do I make a drawable from multiple images?

Question

I have three 9-patch PNG's which together make up the background for a button (left side, middle, right side). I would like to combine these three images together in a drawable which I can specify as the background for a button in XML, something along the lines of:

res/drawable/button_background.xml:

<?xml version="1.0" encoding="utf-8"?>
<nine-patch xmlns:android="http://schemas.android.com/apk/res/android"
android:src="@drawable/button_left_side" />

<nine-patch android:src="@drawable/button_middle" />

<nine-patch android:src="@drawable/button_right_side" />

res/layout/main.xml:

<button android:background="@drawable/button_background" />

Is this possible?

Subaxillary

Answer 1

After some trial-and-error, I was able to solve the problem in a satisfactory way. I simply implemented a Layer-List drawable as follows:

<?xml version="1.0" encoding="utf-8"?>
<layer-list
    xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:drawable="@drawable/btn_left" android:left="0px" />
    <item android:drawable="@drawable/btn_middle" 
        android:left="26px" android:right="26px" />
    <item android:drawable="@drawable/btn_right" android:right="0px" />
</layer-list>

Where the 26px values are the width of the two button side images in pixels.

To use this drawable, simply call it like any other drawable:

<bitmap android:src="@drawable/button_background" />

This works exactly how you would expect it to, with the middle expanding as normal to fit the desired width, and all three images expanding to fit the desired height. I hope others can benefit from this!

Subaxillary

It would give better results if "dp" is used instead of "px". Using px will result in very small left and right most buttons in high density devices. – Arlon