android中获取Application实例的正确方法

Question

获取Application实例哪种方式更合适

1. 在Application.onCreate()中初始化静态字段并提供对其的静态访问

    public class MyApplication extends Application {
   
        private static MyApplication sInstance;
   
        @Override
        public void onCreate() {
            super.onCreate();
            sInstance = this;
        }
   
        public static MyApplication getInstance() {
            return MyApplication.sInstance;
        }
    }
   
    public class MyBroadcastReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            MyApplication application = MyApplication.getInstance();
        }
    }
   

2. 创建以 Context 作为参数的静态方法，并将该 Context 转换为 MyApplication

    public class MyApplication extends Application {
   
        @Override
        public void onCreate() {
            super.onCreate();
        }
   
        public static MyApplication getInstance(Context context) {
            return ((MyApplication) context.getApplicationContext());
        }
    }
   
    public class MyBroadcastReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            MyApplication application = MyApplication.getInstance(context);
        }
    } 
   

3. 按照示例 2 进行操作，但它没有静态访问 MyApplication

    public class MyBroadcastReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            MyApplication application = (MyApplication) context.getApplicationContext();
        }
    }
   

Answer 1

如果您仅需要应用程序的实例，我会推荐方法 3。

如果您的 Application 类中有其他方法，我会推荐方法 1，因为您可以更清楚地执行

MyApplication.getInstance().foo();

方法2只是方法3的捷径，所以我不推荐它。

---

总而言之，这是一个偏好问题。没有一种“正确”的方法，因为它们都会起作用。

Answer 2

(getActivity().getApplication() as MyApplication)

这将返回 MyApplication 的实例