Implement Link for native platforms (#3177)

packages/url_launcher/url_launcher/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 5.7.7
+
+* Introduce the Link widget with an implementation for native platforms.
+
 ## 5.7.6
 
 * Suppress deprecation warning on the `shouldOverrideUrlLoading` method on Android of the `FlutterWebChromeClient` class.

packages/url_launcher/url_launcher/lib/link.dart

@@ -0,0 +1,7 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export 'src/link.dart' show Link;
+export 'package:url_launcher_platform_interface/link.dart'
+    show FollowLink, LinkTarget, LinkWidgetBuilder;

packages/url_launcher/url_launcher/lib/src/link.dart

@@ -0,0 +1,132 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:flutter/widgets.dart';
+import 'package:url_launcher/url_launcher.dart';
+import 'package:url_launcher_platform_interface/link.dart';
+import 'package:url_launcher_platform_interface/url_launcher_platform_interface.dart';
+
+/// A widget that renders a real link on the web, and uses WebViews in native
+/// platforms to open links.
+///
+/// Example link to an external URL:
+///
+/// ```dart
+/// Link(
+///   uri: Uri.parse('https://flutter.dev'),
+///   builder: (BuildContext context, FollowLink followLink) => RaisedButton(
+///     onPressed: followLink,
+///     // ... other properties here ...
+///   )},
+/// );
+/// ```
+///
+/// Example link to a route name within the app:
+///
+/// ```dart
+/// Link(
+///   uri: Uri.parse('/home'),
+///   builder: (BuildContext context, FollowLink followLink) => RaisedButton(
+///     onPressed: followLink,
+///     // ... other properties here ...
+///   )},
+/// );
+/// ```
+class Link extends StatelessWidget implements LinkInfo {
+  /// Called at build time to construct the widget tree under the link.
+  final LinkWidgetBuilder builder;
+
+  /// The destination that this link leads to.
+  final Uri uri;
+
+  /// The target indicating where to open the link.
+  final LinkTarget target;
+
+  /// Whether the link is disabled or not.
+  bool get isDisabled => uri == null;
+
+  /// Creates a widget that renders a real link on the web, and uses WebViews in
+  /// native platforms to open links.
+  Link({
+    Key key,
+    @required this.uri,
+    LinkTarget target,
+    @required this.builder,
+  })  : target = target ?? LinkTarget.defaultTarget,
+        super(key: key);
+
+  LinkDelegate get _effectiveDelegate {
+    return UrlLauncherPlatform.instance.linkDelegate ??
+        DefaultLinkDelegate.create;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return _effectiveDelegate(this);
+  }
+}
+
+/// The default delegate used on non-web platforms.
+///
+/// For external URIs, it uses url_launche APIs. For app route names, it uses
+/// event channel messages to instruct the framework to push the route name.
+class DefaultLinkDelegate extends StatelessWidget {
+  /// Creates a delegate for the given [link].
+  const DefaultLinkDelegate(this.link);
+
+  /// Given a [link], creates an instance of [DefaultLinkDelegate].
+  ///
+  /// This is a static method so it can be used as a tear-off.
+  static DefaultLinkDelegate create(LinkInfo link) {
+    return DefaultLinkDelegate(link);
+  }
+
+  /// Information about the link built by the app.
+  final LinkInfo link;
+
+  bool get _useWebView {
+    if (link.target == LinkTarget.self) return true;
+    if (link.target == LinkTarget.blank) return false;
+    return null;
+  }
+
+  Future<void> _followLink(BuildContext context) async {
+    if (!link.uri.hasScheme) {
+      // A uri that doesn't have a scheme is an internal route name. In this
+      // case, we push it via Flutter's navigation system instead of letting the
+      // browser handle it.
+      final String routeName = link.uri.toString();
+      return pushRouteNameToFramework(context, routeName);
+    }
+
+    // At this point, we know that the link is external. So we use the `launch`
+    // API to open the link.
+    final String urlString = link.uri.toString();
+    if (await canLaunch(urlString)) {
+      await launch(
+        urlString,
+        forceSafariVC: _useWebView,
+        forceWebView: _useWebView,
+      );
+    } else {
+      FlutterError.reportError(FlutterErrorDetails(
+        exception: 'Could not launch link $urlString',
+        stack: StackTrace.current,
+        library: 'url_launcher',
+        context: ErrorDescription('during launching a link'),
+      ));
+    }
+    return Future<void>.value(null);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return link.builder(
+      context,
+      link.isDisabled ? null : () => _followLink(context),
+    );
+  }
+}

packages/url_launcher/url_launcher/pubspec.yaml

@@ -2,7 +2,7 @@ name: url_launcher
 description: Flutter plugin for launching a URL on Android and iOS. Supports
   web, phone, SMS, and email schemes.
 homepage: https://github.com/flutter/plugins/tree/master/packages/url_launcher/url_launcher
-version: 5.7.6
+version: 5.7.7
 
 flutter:
   plugin:
@@ -24,13 +24,13 @@ flutter:
 dependencies:
   flutter:
     sdk: flutter
-  url_launcher_platform_interface: ^1.0.8
+  url_launcher_platform_interface: ^1.0.9
   # The design on https://flutter.dev/go/federated-plugins was to leave
   # this constraint as "any". We cannot do it right now as it fails pub publish
   # validation, so we set a ^ constraint.
   # TODO(amirh): Revisit this (either update this part in the  design or the pub tool).
   # https://github.com/flutter/flutter/issues/46264
-  url_launcher_web: ^0.1.3
+  url_launcher_web: ^0.1.5
   url_launcher_linux: ^0.0.1
   url_launcher_macos: ^0.0.1
   url_launcher_windows: ^0.0.1