Extending the Android Application class and dealing with Singleton

gistfile1.java

package com.devahead.extendingandroidapplication;

import android.app.Application;

public class MyApplication extends Application
{
	@Override
	public void onCreate()
	{
		super.onCreate();

		// Initialize the singletons so their instances
		// are bound to the application process.
		initSingletons();
	}

	protected void initSingletons()
	{
		// Initialize the instance of MySingleton
		MySingleton.initInstance();
	}

	public void customAppMethod()
	{
		// Custom application method
	}
}


//

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
	package="com.devahead.extendingandroidapplication"
	android:versionCode="1"
	android:versionName="1.0">

	<uses-sdk android:minSdkVersion="7"/>

	<application android:icon="@drawable/icon" android:label="@string/app_name"
		android:name="com.devahead.extendingandroidapplication.MyApplication">

		<activity android:name=".MainActivity"
			android:label="@string/app_name">
			<intent-filter>
				<action android:name="android.intent.action.MAIN"/>
				<category android:name="android.intent.category.LAUNCHER"/>
			</intent-filter>
		</activity>

	</application>
</manifest>


//

package com.devahead.extendingandroidapplication;

import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity
{
	protected MyApplication app;

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		// Get the application instance
		app = (MyApplication)getApplication();

		// Call a custom application method
		app.customAppMethod();

		// Call a custom method in MySingleton
		MySingleton.getInstance().customSingletonMethod();

		// Read the value of a variable in MySingleton
		String singletonVar = MySingleton.getInstance().customVar;
	}
}

//
package com.devahead.extendingandroidapplication;

public class MySingleton
{
	private static MySingleton instance;

	public String customVar;

	public static void initInstance()
	{
		if (instance == null)
		{
			// Create the instance
			instance = new MySingleton();
		}
	}

	public static MySingleton getInstance()
	{
		// Return the instance
		return instance;
	}

	private MySingleton()
	{
		// Constructor hidden because this is a singleton
	}

	public void customSingletonMethod()
	{
		// Custom method
	}
}