Why FrameLayout isn't setting Z order correctly in my layout?

Question

I have the following layout (here is presented much simpler design):

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/activity_main">
    <FrameLayout
        android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        >
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hey, badge!"
            android:layout_margin="10dp"
            />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="AAAAA"
            android:layout_margin="10dp"
            android:textSize="12sp"
            android:background="#ff00ff"
            android:padding="10dp"
            android:layout_gravity="top|end"
            />
    </FrameLayout>
</RelativeLayout>

I wish to set TextView with text "AAAA" to act as a badge for Button, i.e. to be placed over the button in its upper right corner, which is not the case.

Instead, when I try this code on HTC One M7 with Lollipop, or on Genymotion Nexus 6 with Lollipop, screen looks something like this:

When I try the same code on Genymotion Nexus 5 with KitKat, everything looks as expected, i.e. first view (button) is shown underneath badge (textview)

Does anyone have any clue what could be wrong here?

Thanks, Deveti

Answer 1

The elevation causes this issue. It was introduced in Lollipop and responsible for z-ordering too. Copy your layout to layout-v21 and set android:elevation="0dp" for the button.