To create an App for Android that supports TWA (Trusted Web Activity), you can use the ChromeSafariBrowser class with the Android-specific option isTrustedWebActivity: true.

Remove the URL bar

Trusted Web Activities require an association between the Android application and the website to be established to remove the URL bar.

This association is created via Digital Asset Links and the association must be established in both ways, linking from the app to the website and from the website to the app.

It is possible to setup the app to website validation and setup Chrome to skip the website to app validation, for debugging purposes.

Check the official Android Integration Guide for more details.

TWA Example

import 'dart:io';

import 'package:flutter/material.dart';
import 'package:flutter_inappwebview/flutter_inappwebview.dart';

class AndroidTWABrowser extends ChromeSafariBrowser {
  @override
  void onOpened() {
    print("Android TWA browser opened");
  }

  @override
  void onCompletedInitialLoad() {
    print("Android TWA browser initial load completed");
  }

  @override
  void onClosed() {
    print("Android TWA browser closed");
  }
}

Future main() async {
  WidgetsFlutterBinding.ensureInitialized();

  if (Platform.isAndroid) {
    await AndroidInAppWebViewController.setWebContentsDebuggingEnabled(true);
  }

  runApp(MaterialApp(home: MyApp()));
}

class MyApp extends StatefulWidget {
  final ChromeSafariBrowser browser = new AndroidTWABrowser();

  @override
  _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Android TWA Example'),
      ),
      body: Center(
        child: ElevatedButton(
            onPressed: () async {
              await widget.browser.open(
                  url: Uri.parse("https://flutter.dev/"),
                  options: ChromeSafariBrowserClassOptions(
                    android: AndroidChromeCustomTabsOptions(
                        isTrustedWebActivity: true),
                  ));
            },
            child: Text("Open Android TWA Browser")),
      ),
    );
  }
}

Create the Android string resource file android/app/src/main/res/values/strings.xml and add the Digital AssetLinks statement below for the https://flutter.dev/ website:

<resources>
    <string name="app_name">Flutter Trusted Web Activity</string>
    <string name="asset_statements">
        [{
            \"relation\": [\"delegate_permission/common.handle_all_urls\"],
            \"target\": {
                \"namespace\": \"web\",
                \"site\": \"https://flutter.dev\"}
        }]
    </string>
</resources>

In the Android App Manifest file android/app/src/main/AndroidManifest.xml, link to the statement by adding a new meta-data tag as a child of the application tag:

<application
    android:label="flutter_inappwebview_example"
    android:icon="@mipmap/ic_launcher">
    <!-- ... -->
    <meta-data
        android:name="asset_statements"
        android:resource="@string/asset_statements" />
    <!-- ... -->
    <activity>
        <!-- ... -->
    </activity>
</application>

To enable debug mode:

  • Open Chrome on the development device, navigate to chrome://flags, search for an item called Enable command line on non-rooted devices and change it to ENABLED and then restart the browser.
  • Next, on the Terminal application of your operating system, use the Android Debug Bridge (installed with Android Studio), and run the following command:
    adb shell "echo '_ --disable-digital-asset-link-verification-for-url=\"https://flutter.dev\"' > /data/local/tmp/chrome-command-line"
    

Close Chrome and re-launch your application from Android Studio. The application should now be shown in full-screen.

Note: It may needed to force close Chrome so it restarts with the correct command line. Go to Android Settings > Apps & notifications > Chrome, and click on Force stop.

This is the result:

Android TWA example.