Correct way to get the instance of Application in android

问题

Which of these ways is more proper for getting the instance of Application

Initialise static field in Application.onCreate() and provide static access to it

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();
    }
}

Create static method which takes Context as param and cast that Context to 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);
    }
}

回答1:

I would recommend method 3 if you only need the instance of the Application.

I would recommend method 1 if you had additional methods in your Application class because you can more clearly do

MyApplication.getInstance().foo();

Method 2 is just a shortcut for method 3, so I wouldn't recommend it.

All in all, it's a matter of preference. There is no one "correct" way because they'll all work.

回答2:

If you really want to Application instance then you're both ways are wrong. This will cause locking while access Instance at the same time. So to overcome this and improve the performance better to use synchronized

Take a look my way below

  public static MyApplication getInstance() {
    if (sInstance == null) {
        synchronized (MyApplication.class) {
            if (sInstance == null) {
                sInstance = new MyApplication();
            }
        }
    }

    return applicationInstance;
}

sInstance that you initialized in onCreate(...)

来源：https://stackoverflow.com/questions/35765077/correct-way-to-get-the-instance-of-application-in-android

标签

android

applicationcontext