Why doesn't `android:foreground` attribute work?

Question

Take a look at this small android app:

MainActivity.java:

package io.github.gsaga.toucheventtest;

import android.support.v7.app.AppCompatActivity;
i         


        

Answer 1

It looks like at one time (API <23) that android:foreground would work with only FrameLayout as VicJordan suggests. However, for API 23+ it appears that android:foreground will work for any view type. See this selection from the View.java source:

case R.styleable.View_foreground:
    if (targetSdkVersion >= Build.VERSION_CODES.M || this instanceof FrameLayout) {
        setForeground(a.getDrawable(attr));
}

Here is an example of android:foreground working on API 28 with the following layout:

Yet, on API 22, we see this:

No foreground image. So, android:foreground works only when the API level is 23+. I agree that this is not really documented, but that is just the way it is.

Update: API 23 seems to have an issue with android:foreground, so let's say android:foreground works on API 24+ for general views.

Second update: Came across a couple of other posts addressing this same issue regarding setForeground() here and here. In the accepted answer to the second question, CommonsWare identifies this as a "documentation bug."