[webview_flutter] get/set a custom User Agent

packages/webview_flutter/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.3.12
+
+* Add an optional `userAgent` property to set a custom User Agent.
+* Add `getUserAgent` to WebViewController. 
+
 ## 0.3.11+3
 
 * Apply the display listeners workaround that was shipped in 0.3.11+1 on
@@ -26,6 +31,7 @@
 
 * Add keyboard text to README.
 
+
 ## 0.3.10+3
 
 * Don't log an unknown setting key error for 'debuggingEnabled' on iOS.

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/FlutterWebView.java

@@ -60,6 +60,10 @@ public class FlutterWebView implements PlatformView, MethodCallHandler {
     }
 
     updateAutoMediaPlaybackPolicy((Integer) params.get("autoMediaPlaybackPolicy"));
+    if (params.containsKey("userAgent")) {
+      String userAgent = (String) params.get("userAgent");
+      updateUserAgent(userAgent);
+    }
     if (params.containsKey("initialUrl")) {
       String url = (String) params.get("initialUrl");
       webView.loadUrl(url);
@@ -130,6 +134,9 @@ public void onMethodCall(MethodCall methodCall, Result result) {
       case "clearCache":
         clearCache(result);
         break;
+      case "getUserAgent":
+        getUserAgent(methodCall, result);
+        break;
       default:
         result.notImplemented();
     }
@@ -241,6 +248,9 @@ private void applySettings(Map<String, Object> settings) {
 
           webView.setWebContentsDebuggingEnabled(debuggingEnabled);
           break;
+        case "userAgent":
+          updateUserAgent((String) settings.get(key));
+          break;
         default:
           throw new IllegalArgumentException("Unknown WebView setting: " + key);
       }
@@ -274,6 +284,15 @@ private void registerJavaScriptChannelNames(List<String> channelNames) {
     }
   }
 
+  private void getUserAgent(MethodCall methodCall, Result result) {
+    String userAgent = webView.getSettings().getUserAgentString();
+    result.success(userAgent);
+  }
+
+  private void updateUserAgent(String userAgent) {
+    webView.getSettings().setUserAgentString(userAgent);
+  }
+
   @Override
   public void dispose() {
     methodChannel.setMethodCallHandler(null);

packages/webview_flutter/example/test_driver/webview.dart

@@ -222,6 +222,94 @@ void main() {
     await resizeCompleter.future;
   });
 
+  test('set custom userAgent', () async {
+    final Completer<WebViewController> controllerCompleter1 =
+        Completer<WebViewController>();
+    final GlobalKey _globalKey = GlobalKey();
+    await pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: WebView(
+          key: _globalKey,
+          initialUrl: 'https://flutter.dev/',
+          javascriptMode: JavascriptMode.unrestricted,
+          userAgent: 'Custom_User_Agent1',
+          onWebViewCreated: (WebViewController controller) {
+            controllerCompleter1.complete(controller);
+          },
+        ),
+      ),
+    );
+    final WebViewController controller1 = await controllerCompleter1.future;
+    final String customUserAgent1 = await controller1.getUserAgent();
+    expect(customUserAgent1, 'Custom_User_Agent1');
+    // rebuild the WebView with a different user agent.
+    await pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: WebView(
+          key: _globalKey,
+          initialUrl: 'https://flutter.dev/',
+          javascriptMode: JavascriptMode.unrestricted,
+          userAgent: 'Custom_User_Agent2',
+        ),
+      ),
+    );
+
+    final String customUserAgent2 = await controller1.getUserAgent();
+    expect(customUserAgent2, 'Custom_User_Agent2');
+  });
+
+  test('use default platform userAgent after webView is rebuilt', () async {
+    final Completer<WebViewController> controllerCompleter =
+        Completer<WebViewController>();
+    final GlobalKey _globalKey = GlobalKey();
+    // Build the webView with no user agent to get the default platform user agent.
+    await pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: WebView(
+          key: _globalKey,
+          initialUrl: 'https://flutter.dev/',
+          javascriptMode: JavascriptMode.unrestricted,
+          onWebViewCreated: (WebViewController controller) {
+            controllerCompleter.complete(controller);
+          },
+        ),
+      ),
+    );
+    final WebViewController controller = await controllerCompleter.future;
+    final String defaultPlatformUserAgent = await controller.getUserAgent();
+    // rebuild the WebView with a custom user agent.
+    await pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: WebView(
+          key: _globalKey,
+          initialUrl: 'https://flutter.dev/',
+          javascriptMode: JavascriptMode.unrestricted,
+          userAgent: 'Custom_User_Agent',
+        ),
+      ),
+    );
+    final String customUserAgent = await controller.getUserAgent();
+    expect(customUserAgent, 'Custom_User_Agent');
+    // rebuilds the WebView with no user agent.
+    await pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: WebView(
+          key: _globalKey,
+          initialUrl: 'https://flutter.dev/',
+          javascriptMode: JavascriptMode.unrestricted,
+        ),
+      ),
+    );
+
+    final String customUserAgent2 = await controller.getUserAgent();
+    expect(customUserAgent2, defaultPlatformUserAgent);
+  });
+
   group('Media playback policy', () {
     String audioTestBase64;
     setUpAll(() async {

packages/webview_flutter/ios/Classes/FlutterWebView.m

@@ -118,6 +118,8 @@ - (void)onMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
     [self onRemoveJavaScriptChannels:call result:result];
   } else if ([[call method] isEqualToString:@"clearCache"]) {
     [self clearCache:result];
+  } else if ([[call method] isEqualToString:@"getUserAgent"]) {
+    [self onGetUserAgent:call result:result];
   } else {
     result(FlutterMethodNotImplemented);
   }
@@ -250,6 +252,9 @@ - (NSString*)applySettings:(NSDictionary<NSString*, id>*)settings {
       _navigationDelegate.hasDartNavigationDelegate = [hasDartNavigationDelegate boolValue];
     } else if ([key isEqualToString:@"debuggingEnabled"]) {
       // no-op debugging is always enabled on iOS.
+    } else if ([key isEqualToString:@"userAgent"]) {
+      NSString* userAgent = settings[key];
+      [self updateUserAgent:[userAgent isEqual:[NSNull null]] ? nil : userAgent];
     } else {
       [unknownKeys addObject:key];
     }
@@ -349,4 +354,29 @@ - (void)registerJavaScriptChannels:(NSSet*)channelNames
   }
 }
 
+- (void)onGetUserAgent:(FlutterMethodCall*)call result:(FlutterResult)result {
+  [_webView
+      evaluateJavaScript:@"navigator.userAgent"
+       completionHandler:^(NSString* userAgent, NSError* error) {
+         if (error) {
+           result([FlutterError
+               errorWithCode:@"userAgent_failed"
+                     message:@"Failed to get UserAgent"
+                     details:[NSString stringWithFormat:
+                                           @"webview_flutter: failed evaluating JavaScript: %@",
+                                           [error localizedDescription]]]);
+         } else {
+           result(userAgent);
+         }
+       }];
+}
+
+- (void)updateUserAgent:(NSString*)userAgent {
+  if (@available(iOS 9.0, *)) {
+    [_webView setCustomUserAgent:userAgent];
+  } else {
+    NSLog(@"Updating UserAgent is not supported for Flutter WebViews prior to iOS 9.");
+  }
+}
+
 @end

packages/webview_flutter/lib/platform_interface.dart

@@ -152,18 +152,74 @@ abstract class WebViewPlatformController {
     throw UnimplementedError(
         "WebView removeJavascriptChannels is not implemented on the current platform");
   }
+
+  /// Returns the value used for the HTTP User-Agent: request header in subsequent HTTP requests.
+  Future<String> getUserAgent() {
+    throw UnimplementedError(
+        "WebView getUserAgent is not implemented on the current platform");
+  }
+}
+
+/// A single setting for configuring a WebViewPlatform which may be absent.
+class WebSetting<T> {
+  /// Constructs an absent setting instance.
+  ///
+  /// The [isPresent] field for the instance will be false.
+  ///
+  /// Accessing [value] for an absent instance will throw.
+  WebSetting.absent()
+      : _value = null,
+        isPresent = false;
+
+  /// Constructs a setting of the given `value`.
+  ///
+  /// The [isPresent] field for the instance will be true.
+  WebSetting.of(T value)
+      : _value = value,
+        isPresent = true;
+
+  final T _value;
+
+  /// The setting's value.
+  ///
+  /// Throws if [WebSetting.isPresent] is false.
+  T get value {
+    if (!isPresent) {
+      throw StateError('Cannot access a value of an absent WebSetting');
+    }
+    assert(isPresent);
+    return _value;
+  }
+
+  /// True when this web setting instance contains a value.
+  ///
+  /// When false the [WebSetting.value] getter throws.
+  final bool isPresent;
+
+  @override
+  bool operator ==(Object other) {
+    if (other.runtimeType != runtimeType) return false;
+    final WebSetting<T> typedOther = other;
+    return typedOther.isPresent == isPresent && typedOther._value == _value;
+  }
+
+  @override
+  int get hashCode => hashValues(_value, isPresent);
 }
 
 /// Settings for configuring a WebViewPlatform.
 ///
 /// Initial settings are passed as part of [CreationParams], settings updates are sent with
 /// [WebViewPlatform#updateSettings].
+///
+/// The `userAgent` parameter must not be null.
 class WebSettings {
   WebSettings({
     this.javascriptMode,
     this.hasNavigationDelegate,
     this.debuggingEnabled,
-  });
+    @required this.userAgent,
+  }) : assert(userAgent != null);
 
   /// The JavaScript execution mode to be used by the webview.
   final JavascriptMode javascriptMode;
@@ -176,9 +232,19 @@ class WebSettings {
   /// See also: [WebView.debuggingEnabled].
   final bool debuggingEnabled;
 
+  /// The value used for the HTTP `User-Agent:` request header.
+  ///
+  /// If [userAgent.value] is null the platform's default user agent should be used.
+  ///
+  /// An absent value ([userAgent.isPresent] is false) represents no change to this setting from the
+  /// last time it was set.
+  ///
+  /// See also [WebView.userAgent].
+  final WebSetting<String> userAgent;
+
   @override
   String toString() {
-    return 'WebSettings(javascriptMode: $javascriptMode, hasNavigationDelegate: $hasNavigationDelegate, debuggingEnabled: $debuggingEnabled)';
+    return 'WebSettings(javascriptMode: $javascriptMode, hasNavigationDelegate: $hasNavigationDelegate, debuggingEnabled: $debuggingEnabled, userAgent: $userAgent,)';
   }
 }
 
@@ -190,6 +256,7 @@ class CreationParams {
     this.initialUrl,
     this.webSettings,
     this.javascriptChannelNames,
+    this.userAgent,
     this.autoMediaPlaybackPolicy =
         AutoMediaPlaybackPolicy.require_user_action_for_all_media_types,
   }) : assert(autoMediaPlaybackPolicy != null);
@@ -217,12 +284,17 @@ class CreationParams {
   // to PlatformWebView.
   final Set<String> javascriptChannelNames;
 
+  /// The value used for the HTTP User-Agent: request header.
+  ///
+  /// When null the platform's webview default is used for the User-Agent header.
+  final String userAgent;
+
   /// Which restrictions apply on automatic media playback.
   final AutoMediaPlaybackPolicy autoMediaPlaybackPolicy;
 
   @override
   String toString() {
-    return '$runtimeType(initialUrl: $initialUrl, settings: $webSettings, javascriptChannelNames: $javascriptChannelNames)';
+    return '$runtimeType(initialUrl: $initialUrl, settings: $webSettings, javascriptChannelNames: $javascriptChannelNames, UserAgent: $userAgent)';
   }
 }
 

packages/webview_flutter/lib/src/webview_method_channel.dart

@@ -103,6 +103,11 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
         'removeJavascriptChannels', javascriptChannelNames.toList());
   }
 
+  @override
+  Future<String> getUserAgent() {
+    return _channel.invokeMethod('getUserAgent');
+  }
+
   /// Method channel implementation for [WebViewPlatform.clearCookies].
   static Future<bool> clearCookies() {
     return _cookieManagerChannel
@@ -119,9 +124,17 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
       map[key] = value;
     }
 
+    void _addSettingIfPresent<T>(String key, WebSetting<T> setting) {
+      if (!setting.isPresent) {
+        return;
+      }
+      map[key] = setting.value;
+    }
+
     _addIfNonNull('jsMode', settings.javascriptMode?.index);
     _addIfNonNull('hasNavigationDelegate', settings.hasNavigationDelegate);
     _addIfNonNull('debuggingEnabled', settings.debuggingEnabled);
+    _addSettingIfPresent('userAgent', settings.userAgent);
     return map;
   }
 
@@ -135,6 +148,7 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
       'initialUrl': creationParams.initialUrl,
       'settings': _webSettingsToMap(creationParams.webSettings),
       'javascriptChannelNames': creationParams.javascriptChannelNames.toList(),
+      'userAgent': creationParams.userAgent,
       'autoMediaPlaybackPolicy': creationParams.autoMediaPlaybackPolicy.index,
     };
   }