myapplication 单例写法

MyApplication extends Application
 private static MyApplication myApplication = null;

oncreate中：

 @Override

    public void onCreate () {

        super.onCreate();

        myApplication = this;

    }

getInstance 函数

 public static MyApplication getInstance(){

        return myApplication;

    }

最重要一点，清单文件中：application 节点下：

  android:name=".MyApplication"