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>
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); } }
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