import com.dstaley.ReactNativeChromeCustomTabs.ChromeCustomTabsPackage; // <-- Import 
 
public class MainActivity extends Activity implements DefaultHardwareBackBtnHandler {
 
    private ReactInstanceManager mReactInstanceManager;
    private ReactRootView mReactRootView;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mReactRootView = new ReactRootView(this);
 
        mReactInstanceManager = ReactInstanceManager.builder()
                .setApplication(getApplication())
                .setBundleAssetName("index.android.bundle")
                .setJSMainModuleName("index.android")
                .addPackage(new MainReactPackage())
                .addPackage(new ChromeCustomTabsPackage(this))          // <-- Register 
                .setUseDeveloperSupport(BuildConfig.DEBUG)
                .setInitialLifecycleState(LifecycleState.RESUMED)
                .build();
 
        mReactRootView.startReactApplication(mReactInstanceManager, "DemoReactNativeCustomTabs", null);
 
        setContentView(mReactRootView);
    }