Example injecting React Native module ReactPackages.

MainApplication.java

package com.testing;

import android.app.Application;

import com.facebook.react.ReactApplication;
import com.facebook.react.ReactNativeHost;
import com.facebook.react.ReactPackage;
import com.facebook.react.shell.MainReactPackage;
import com.facebook.soloader.SoLoader;

import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.List;

import io.invertase.firebase.app.ReactNativeFirebaseAppPackage;

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

    @Override
    protected List<ReactPackage> getPackages() {

      ReactPackage analytics = null;
      String className = "io.invertase.firebase.analytics.ReactNativeFirebaseAnalyticsPackage";

      try {
        analytics = (ReactPackage) Class.forName(className).getConstructors()[0].newInstance();
      } catch (ClassNotFoundException e) {
        e.printStackTrace();
      } catch (IllegalAccessException e) {
        e.printStackTrace();
      } catch (InstantiationException e) {
        e.printStackTrace();
      } catch (InvocationTargetException e) {
        e.printStackTrace();
      }

      List<ReactPackage> packages = new ArrayList<>();

      packages.add(new MainReactPackage());
      packages.add(new ReactNativeFirebaseAppPackage());

      if (analytics != null) {
        packages.add(analytics);
      }

      return packages;
    }
  };

  @Override
  public ReactNativeHost getReactNativeHost() {
    return mReactNativeHost;
  }

  @Override
  public void onCreate() {
    super.onCreate();
    SoLoader.init(this, /* native exopackage */ false);
  }

}