OnSaveInstantState Method

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_height="wrap_content"
        android:inputType="number"
        android:ems="10"
        android:id="@+id/editText"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="58dp"
        android:hint="First Number" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="10"
        android:id="@+id/editText2"
        android:layout_below="@+id/editText"
        android:layout_centerHorizontal="true"
        android:hint="Second Number" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="add"
        android:onClick="add"
        android:id="@+id/button"
        android:layout_below="@+id/editText2"
        android:layout_centerHorizontal="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Result"
        android:id="@+id/textView"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/button" />
</RelativeLayout>

MainActivity.java

package com.blogspot.csdevbin.onsaveinstantstatemethod;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    EditText editText1, editText2;
    TextView tv;
    int result;

   
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editText1 = (EditText) findViewById(R.id.editText);
        editText2 = (EditText) findViewById(R.id.editText2);
        tv = (TextView) findViewById(R.id.textView);

        if (savedInstanceState != null) {
             result = savedInstanceState.getInt("result");
            tv.setText("addition is : " + result);
        }
    }

    public void add(View v) {
        String s1 = editText1.getText().toString();
        String s2 = editText2.getText().toString();

         result = Integer.parseInt(s1) + Integer.parseInt(s2);

        tv.setText("addition is : " + result);
    }

    protected void onSavedInstantState(Bundle Outstate) {
            super.onSaveInstanceState(Outstate);
           Outstate.putInt("result",result);
    }
}