kasus_11.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context=".Kasus11">

    <Button
        android:id="@+id/button_kasus_11"
        android:text="CLICK ME!"
        android:textColor="#FFFFFF"
        android:textSize="30sp"
        android:shadowColor="#FF0000"
        android:shadowDx="2"
        android:shadowDy="2"
        android:shadowRadius="5"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        android:onClick="showText"/>

</android.support.constraint.ConstraintLayout>