In android app when ever activities changes their orientation (portal/landscape) ,they are going to loss their UI state. To avoid this, we use OnSaveInstantState Method. activity_main.xml <?xml version="1.0" encoding="utf-8"?> <RelativeLayout 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: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.blogspot.csdevbin.onsaveinstantstatemethod.MainActivity">     <EditText         android:layout_width="wrap_content"         android:layout_...