You cannot set theme as a background of view. In your code below line may cause the problem.
android:background="@style/AppBaseTheme"
Instead of it you should use drawable. F
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/viewBackground"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white"
tools:context=".MainActivity" >
<TextView android:id="@+id/textTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="86dp"
android:text="@string/hello_world" />
<Button android:id="@+id/buttonFlashlight"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textTitle"
android:layout_centerHorizontal="true"
android:layout_marginTop="36dp"
android:text="@string/hello_world" />
</RelativeLayout>