tests/LockTaskTests/res/layout/activity_launch.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/root_launch"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.google.android.example.locktasktests.LaunchActivity" >

    <Button
        android:id="@+id/button_try_lock"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onTryLock"
        android:text="@string/try_lock" />
    <Button
        android:id="@+id/button_try_unlock"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onTryUnlock"
        android:text="@string/try_unlock" />
    <Button
        android:id="@+id/button_launch_main"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onLaunchMain"
        android:text="@string/launch_main" />

</LinearLayout>