Preview the layout during editing XML files.

preview_layout.xml

<?xml version="1.0" encoding="utf-8" ?>
<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"
              tools:context="com.example.PreviewLayoutActivity">
    <TextView
        android:id="@+id/answer_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="24dp"
        tools:text="Answer"/>
</LinearLayout>

1. Adding tools:context="your.activity" to super layout
2. Using tools:text="Strings you want to preview" in the compotent which you want to preview

The string Answer will only display in the Android Studio preview window and wont show in running app.