Extending MainApplication & AppDelegate

There are some React Native modules that will require you to extend MainApplication on android or extend AppDelegate on iOS.

Extending MainApplication on Android

This is usually required by native modules that want to do some background work when app is in killed state. For example a native module that wakes up the app when user taps on a Notification.

Create a application.android.ts at the root of your project:

/* eslint-disable @typescript-eslint/no-unused-vars */
@NativeClass()
@JavaProxy('com.tns.NativeScriptApplication')
class Application extends com.facebook.react.ReactCustomApplication {
  public onCreate(): void {
    super.onCreate();
  }

  public attachBaseContext(baseContext: android.content.Context) {
    super.attachBaseContext(baseContext);
  }
}

Open your project’s webpack.config.js file and add the custom NativeScriptApplication entry.

webpack.chainWebpack((config) => {
  config.entry('application').add('./application.android');
});

Extending AppDelegate on iOS

As an example react-native-background-fetch module requires that we call TSBackgroundFetch.sharedInstance().didFinishLaunching() when our app launches in AppDelegate. Here’s how we can achieve this in NativeScript.

import { Application } from '@nativescript/core';

if (global.isIOS) {
  @NativeClass()
  @ObjCClass(UIApplicationDelegate)
  class MyDelegate extends UIResponder implements UIApplicationDelegate {
    applicationDidFinishLaunchingWithOptions(application: UIApplication, launchOptions: NSDictionary<string, any>): boolean {
      //@ts-ignore
      TSBackgroundFetch.sharedInstance.didFinishLaunching();
      return true;
    }
  }
  Application.ios.delegate = MyDelegate;
}

import { Application } from '@nativescript/core';

if (global.isIOS) {
  const MyDelegate = UIResponder.extend(
    {
      applicationDidFinishLaunchingWithOptions(application, launchOptions) {
        TSBackgroundFetch.sharedInstance.didFinishLaunching();
        return true;
      },
    },
    {
      name: 'MyDelegate',
      protocols: [UIApplicationDelegate],
    }
  );

  Application.ios.delegate = MyDelegate;
}