Android - Draw outline of views on old Android, when the developer tools don't display outline of views.

drawable-debug_outline.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item>
        <shape android:shape="rectangle">
            <stroke
                android:width="2dp"
                android:color="@android:color/holo_blue_dark"/>
        </shape>
    </item>

    <item
        android:left="10dp"
        android:right="10dp">
        <shape>
            <stroke
                android:width="2dp"
                android:color="@android:color/holo_red_light"/>
        </shape>
    </item>

    <item
        android:top="10dp"
        android:bottom="10dp">
        <shape>
            <stroke
                android:width="2dp"
                android:color="@android:color/holo_red_light"/>
        </shape>
    </item>

    <item
        android:left="2dp"
        android:right="2dp"
        android:top="2dp"
        android:bottom="2dp">
        <shape android:shape="rectangle">
            <solid
                android:color="@android:color/white"/>
        </shape>
    </item>
</layer-list>

layout-example.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/btn_chooser"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/btn_text_chooser"
        android:background="@drawable/debug_outline"/>

</LinearLayout>