覆盖 onCreate()，在你的应用中，

Override onCreate(), in your app,

@Override
public void onCreate() {
    super.onCreate();

然后在那里做.不要忘记在 AndroidManifest 中声明你的 Application 子类.例如

and do it there. Don't forget to declare your Application subclass in the AndroidManifest as well. E.g.

  <application
        android:name="App"