How to get Native Android Activity in React Native

Question

I've been trying to get the activity in a React Native app, but to no success.

When I try getting it from public class MainActivity extends ReactActivity I get the following error when I try using the Activity on a android.app.Activity.getWindowManager() meaning the Activity \ Context was null in the first place:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.WindowManager android.app.Activity.getWindowManager()' on a null object reference

When I try getting it from public class MainApplication extends Application implements ReactApplication class I get the error :

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.WindowManager android.app.Activity.getWindowManager()' on a null object reference  

I do understand that this.getApplicationContext() does not guarantee you an Activity.

I have tried getting the class from within all the methods in the classes.

How should I go about it? What am I doing wrong?

Thank you all in advance.

MainActivity :

public class MainActivity extends ReactActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    // Set the theme to AppTheme BEFORE onCreate to support 
    // coloring the background, status bar, and navigation bar.
    // This is required for expo-splash-screen.
    setTheme(R.style.AppTheme);
    super.onCreate(null);
  }

  /**
   * Returns the name of the main component registered from JavaScript.
   * This is used to schedule rendering of the component.
   */
  @Override
  protected String getMainComponentName() {
    return "main";
  }

  /**
   * Returns the instance of the {@link ReactActivityDelegate}. There the RootView is created and
   * you can specify the renderer you wish to use - the new renderer (Fabric) or the old renderer
   * (Paper).
   */
  @Override
  protected ReactActivityDelegate createReactActivityDelegate() {
    return new ReactActivityDelegateWrapper(this, BuildConfig.IS_NEW_ARCHITECTURE_ENABLED,
      new MainActivityDelegate(this, getMainComponentName())
    );
  }

  /**
   * Align the back button behavior with Android S
   * where moving root activities to background instead of finishing activities.
   * @see <a href="https://developer.android.com/reference/android/app/Activity#onBackPressed()">onBackPressed</a>
   */
  @Override
  public void invokeDefaultOnBackPressed() {
    if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.R) {
      if (!moveTaskToBack(false)) {
        // For non-root activities, use the default implementation to finish them.
        super.invokeDefaultOnBackPressed();
      }
      return;
    }

    // Use the default back button implementation on Android S
    // because it's doing more than {@link Activity#moveTaskToBack} in fact.
    super.invokeDefaultOnBackPressed();
  }

  public static class MainActivityDelegate extends ReactActivityDelegate {
    public MainActivityDelegate(ReactActivity activity, String mainComponentName) {
      super(activity, mainComponentName);
    }

    @Override
    protected ReactRootView createRootView() {
      ReactRootView reactRootView = new ReactRootView(getContext());
      // If you opted-in for the New Architecture, we enable the Fabric Renderer.
      reactRootView.setIsFabric(BuildConfig.IS_NEW_ARCHITECTURE_ENABLED);
      return reactRootView;
    }

    @Override
    protected boolean isConcurrentRootEnabled() {
      // If you opted-in for the New Architecture, we enable Concurrent Root (i.e. React 18).
      // More on this on https://reactjs.org/blog/2022/03/29/react-v18.html
      return BuildConfig.IS_NEW_ARCHITECTURE_ENABLED;
    }
  }
}

MainApplication :

public class MainApplication extends Application implements ReactApplication {
  private final ReactNativeHost mReactNativeHost = new ReactNativeHostWrapper(
    this,
    new ReactNativeHost(this) {
    @Override
    public boolean getUseDeveloperSupport() {
      return BuildConfig.DEBUG;
    }

    @Override
    protected List<ReactPackage> getPackages() {
      @SuppressWarnings("UnnecessaryLocalVariable")
      List<ReactPackage> packages = new PackageList(this).getPackages();
      // Packages that cannot be autolinked yet can be added manually here, for example:
      // packages.add(new MyReactNativePackage());
      return packages;
    }

    @Override
    protected String getJSMainModuleName() {
      return "index";
    }
  });

  private final ReactNativeHost mNewArchitectureNativeHost =
      new ReactNativeHostWrapper(this, new MainApplicationReactNativeHost(this));

  @Override
  public ReactNativeHost getReactNativeHost() {
    if (BuildConfig.IS_NEW_ARCHITECTURE_ENABLED) {
      return mNewArchitectureNativeHost;
    } else {
      return mReactNativeHost;
    }
  }

  @Override
  public void onCreate() {
    super.onCreate();
    // If you opted-in for the New Architecture, we enable the TurboModule system
    ReactFeatureFlags.useTurboModules = BuildConfig.IS_NEW_ARCHITECTURE_ENABLED;
    SoLoader.init(this, /* native exopackage */ false);

    initializeFlipper(this, getReactNativeHost().getReactInstanceManager());
    ApplicationLifecycleDispatcher.onApplicationCreate(this);
  }

  @Override
  public void onConfigurationChanged(@NonNull Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    ApplicationLifecycleDispatcher.onConfigurationChanged(this, newConfig);
  }

  /**
   * Loads Flipper in React Native templates. Call this in the onCreate method with something like
   * initializeFlipper(this, getReactNativeHost().getReactInstanceManager());
   *
   * @param context
   * @param reactInstanceManager
   */
  private static void initializeFlipper(
      Context context, ReactInstanceManager reactInstanceManager) {
    if (BuildConfig.DEBUG) {
      try {
        /*
         We use reflection here to pick up the class that initializes Flipper,
        since Flipper library is not available in release mode
        */
        Class<?> aClass = Class.forName("rev.ca.ReactNativeFlipper");
        aClass
            .getMethod("initializeFlipper", Context.class, ReactInstanceManager.class)
            .invoke(null, context, reactInstanceManager);
      } catch (ClassNotFoundException e) {
        e.printStackTrace();
      } catch (NoSuchMethodException e) {
        e.printStackTrace();
      } catch (IllegalAccessException e) {
        e.printStackTrace();
      } catch (InvocationTargetException e) {
        e.printStackTrace();
      }
    }
  }
}