activity_source.xml

<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"
    android:background="@android:color/holo_orange_dark"
    android:padding="50dp"
    tools:context=".SourceActivity">


    <TextView
        android:id="@+id/sourceView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="@string/title_activity_source"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <EditText
        android:id="@+id/forwardValueEdit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:background="@android:color/background_light"
        android:padding="5dp"
        android:text="@string/empty" />

    <Button
        android:id="@+id/targetParameterlessButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:onClick="onClickTargetParameterless"
        android:text="@string/startTargetParameterless" />

    <Button
        android:id="@+id/targetParametricButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:onClick="onClickTargetParametric"
        android:text="@string/startTargetParametric" />

    <Button
        android:id="@+id/targetResultingButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:onClick="onClickTargetExpecting"
        android:text="@string/startTargetExpecting" />

</LinearLayout>