Saving Activity state in Android using Shared Preferences

How to save the activity instance using Shared Preferences

As you all know that there are many situations where we need to store the instance of the activity so that when the user returns to the application,the instance should remain the same.

The best example is whenever you play the game, the Highest score is changed when you create a new highest score. And whenever you return the game the score is the new high score.

So we'll learn the new concept of Shared Preferences i.e used to store the value in the application database till the application is uninstalled.

1.activity_main.xml

<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=".MainActivity" >

    <EditText

        android:id="@+id/editText1"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:ems="10" 

        android:inputType="text">

    </EditText>

    <TextView

        android:id="@+id/textView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_below="@+id/button1"

        android:layout_marginRight="19dp"

        android:layout_marginTop="38dp"

        android:text="TextView" />

    <Button

        android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignLeft="@+id/editText1"

        android:layout_below="@+id/editText1"

        android:text="Register the Score" />

</RelativeLayout>

2. MainActivity.java

package com.sri.score;

import android.app.Activity;

import android.content.SharedPreferences;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends Activity {

EditText e1;

Button b;

TextView tv;

int i;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

tv = (TextView) findViewById(R.id.textView1);

e1=(EditText) findViewById(R.id.editText1);

b=(Button) findViewById(R.id.button1);

b.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

   i = Integer.parseInt(e1.getText().toString());

   tv.setText("the score changed to " + i);

   Toast.makeText(getApplicationContext(), "score registered", Toast.LENGTH_SHORT).show();

}

});

if (savedInstanceState == null)

i = 0;

SharedPreferences preferences = getPreferences(MODE_PRIVATE);

// Set the values of the UI

int j = preferences.getInt("i", i);

tv.setText("the score now is " + j);

}

@Override

protected void onPause() {

// TODO Auto-generated method stub

super.onPause();

SharedPreferences preferences = getPreferences(MODE_PRIVATE);

SharedPreferences.Editor editor = preferences.edit();

// Put the values from the UI

editor.putInt("i", i);

editor.commit();

}

}

3.Run the application.

First your application value is 0, next your new score is registered. exit the application and open app once again to see the value remains as you exited previously.