Layer List Drawables

BeatBox is looking good. You now have round buttons, and they visually respond to presses. Time for something a little more advanced.

Layer list drawables allow you to combine two XML drawables into one. Armed with this tool, add a dark ring around your button when it is in the pressed state.

Listing 22.7  Using a layer list drawable (res/drawable/button_beat_box_pressed.xml)

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape xmlns:android="http://schemas.android.com/apk/res/android"
            android:shape="oval">

          <solid android:color="@color/red"/>
        </shape>
    </item>
    <item>
        <shape android:shape="oval">

            <stroke android:width="4dp"
                    android:color="@color/dark_red"/>
        </shape>
    </item> ...

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