Android drawable resources include the ability to provide and XML resource that specifies a different name for it’s bitmap resource.  It is an especially handy mechanism for library code to refer to a specific drawable resource that your app provides under a different name.

For example a drawable xml named “app_icon.xml” could contain:

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

If you used this kind of resource as your application’s icon resource inside your AndroidManifest.xml file, though, you have a problem. While technically, the app will function normally, the Android Market tries to check to make sure your app’s icon meets some guideline criteria and cannot handle an XML drawable. Android Market will refuse to upload your app and tell you “The icon for your application is not valid. Please use a 48×48 PNG.”

If you use XML drawables, please keep this limitation in mind and do not reference them inside your AndroidManifest.xml.