singleton pattern in Android

 A singleton in Java is a class for which only one instance can be created provides a global point of access this instance. The singleton pattern describe how this can be archived.

Singletons are useful to provide a unique source of data or functionality to other Java Objects. For example you may use a singleton to access your data model from within your application or to define logger which the rest of the application can use.

package com.example.singletone;

 

import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.widget.Toast;

 

public class ActivityA extends Activity {

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

 

        //Show the string value defined by the private constructor

        Toast.makeText(getApplicationContext(),Singleton.getInstance().getString(), Toast.LENGTH_LONG).show();

 

        //Change the string value and launch intent to ActivityB

        Singleton.getInstance().setString("Singleton");

        Intent intent = new Intent(getApplicationContext(),ActivityB.class);

        this.startActivity(intent);

    }

}




and 





package com.example. singletone;

 



public class Singleton {

    private static Singleton mInstance = null;

 

    private String mString;

 

    private Singleton(){

        mString = "Hello";

    }

 

    public static Singleton getInstance(){

        if(mInstance == null)

        {

            mInstance = new Singleton();

        }

        return mInstance;

    }

 

    public String getString(){

        return this.mString;

    }

 

    public void setString(String value){

        mString = value;

    }

}