package kankan.wheel.demo;

 import java.util.LinkedList;

 import java.util.List;

 import android.app.Activity;

 import android.app.Application;

 import android.util.Log;

 public class MyApplication extends Application {

     private static List<Activity> activityList = new LinkedList<Activity>();

     private static MyApplication instance;

     public MyApplication() {

     }

     // 单例模式中获取唯一的MyApplication实例

     public static MyApplication getInstance() {

         if (null == instance) {

             instance = new MyApplication();

         }

         return instance;

     }

     // 添加Activity到容器中

     public void addActivity(Activity activity) {

         activityList.add(activity);

     }

     // 遍历所有Activity并finish

     public void exit() {

         for (Activity activity : activityList) {

             RLog.i("-aa_aa-", "destroy all activity: " + activity.toString() + " !!!");

             activity.finish();

         }

         System.exit(0);

     }

 }

MyApplication.getInstance().addActivity(this);

	public void onBackPressed() {

		MyApplication myApplication = (MyApplication) WheelDemo.this

				.getApplication();

		Log.i("exit app:", "exit ok!");

		myApplication.exit();

	}