[webview_flutter] get/set a custom User Agent

packages/webview_flutter/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.3.11
+
+* Add an optional `userAgent` property to set a custom User Agent.
+  Add `getUserAgent` to WebViewController. 
+
 ## 0.3.10+5
 
 * Add dependency on `androidx.annotation:annotation:1.0.0`.
@@ -6,6 +11,7 @@
 
 * 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

@@ -55,6 +55,11 @@ public class FlutterWebView implements PlatformView, MethodCallHandler {
       String url = (String) params.get("initialUrl");
       webView.loadUrl(url);
     }
+
+    if (params.containsKey("userAgent")) {
+      String userAgent = (String) params.get("userAgent");
+      updateUserAgent(userAgent);
+    }
   }
 
   @Override
@@ -121,6 +126,9 @@ public void onMethodCall(MethodCall methodCall, Result result) {
       case "clearCache":
         clearCache(result);
         break;
+      case "getUserAgent":
+        getUserAgent(methodCall, result);
+        break;
       default:
         result.notImplemented();
     }
@@ -232,6 +240,9 @@ 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);
       }
@@ -258,6 +269,15 @@ 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/lib/main.dart

@@ -53,6 +53,7 @@ class _WebViewExampleState extends State<WebViewExample> {
           onWebViewCreated: (WebViewController webViewController) {
             _controller.complete(webViewController);
           },
+          userAgent: 'Flutter_Custom_Agent',
           // TODO(iskakaushik): Remove this when collection literals makes it to stable.
           // ignore: prefer_collection_literals
           javascriptChannels: <JavascriptChannel>[

packages/webview_flutter/example/test_driver/webview.dart

@@ -132,6 +132,49 @@ void main() {
     await controller.evaluateJavascript('Echo.postMessage("hello");');
     expect(messagesReceived, equals(<String>['hello']));
   });
+
+  test('userAgent', () async {
+    final Completer<WebViewController> controllerCompleter1 =
+        Completer<WebViewController>();
+    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');
+
+    // rebuilds a WebView with a different user agent.
+    final Completer<WebViewController> controllerCompleter2 =
+        Completer<WebViewController>();
+    await pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: WebView(
+          key: GlobalKey(),
+          initialUrl: 'https://flutter.dev/',
+          javascriptMode: JavascriptMode.unrestricted,
+          userAgent: 'Custom_User_Agent2',
+          onWebViewCreated: (WebViewController controller) {
+            controllerCompleter2.complete(controller);
+          },
+        ),
+      ),
+    );
+    final WebViewController controller2 = await controllerCompleter2.future;
+    final String customUserAgent2 = await controller2.getUserAgent();
+    expect(customUserAgent2, 'Custom_User_Agent2');
+  });
 }
 
 Future<void> pumpWidget(Widget widget) {

packages/webview_flutter/ios/Classes/FlutterWebView.m

@@ -114,6 +114,8 @@ - (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);
   }
@@ -246,6 +248,9 @@ - (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];
     }
@@ -321,4 +326,29 @@ - (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

@@ -152,6 +152,11 @@ abstract class WebViewPlatformController {
     throw UnimplementedError(
         "WebView removeJavascriptChannels is not implemented on the current platform");
   }
+
+  Future<String> getUserAgent() {
+    throw UnimplementedError(
+        "WebView getUserAgent is not implemented on the current platform");
+  }
 }
 
 /// Settings for configuring a WebViewPlatform.
@@ -163,6 +168,7 @@ class WebSettings {
     this.javascriptMode,
     this.hasNavigationDelegate,
     this.debuggingEnabled,
+    this.userAgent,
   });
 
   /// The JavaScript execution mode to be used by the webview.
@@ -176,16 +182,24 @@ class WebSettings {
   /// See also: [WebView.debuggingEnabled].
   final bool debuggingEnabled;
 
+  /// The User Agent used for all following requests
+  ///
+  /// See also [WebView.userAgent]
+  final String userAgent;
+
   @override
   String toString() {
-    return 'WebSettings(javascriptMode: $javascriptMode, hasNavigationDelegate: $hasNavigationDelegate, debuggingEnabled: $debuggingEnabled)';
+    return 'WebSettings(javascriptMode: $javascriptMode, hasNavigationDelegate: $hasNavigationDelegate, debuggingEnabled: $debuggingEnabled, userAgent: $userAgent,)';
   }
 }
 
 /// Configuration to use when creating a new [WebViewPlatformController].
 class CreationParams {
   CreationParams(
-      {this.initialUrl, this.webSettings, this.javascriptChannelNames});
+      {this.initialUrl,
+      this.webSettings,
+      this.javascriptChannelNames,
+      this.userAgent});
 
   /// The initialUrl to load in the webview.
   ///
@@ -210,9 +224,14 @@ class CreationParams {
   // to PlatformWebView.
   final Set<String> javascriptChannelNames;
 
+  /// The User Agent used for all following requests
+  ///
+  /// When null, the default User Agent of the Android/iOS WebView is used
+  final String userAgent;
+
   @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 mplementation for [WebViewPlatform.clearCookies].
   static Future<bool> clearCookies() {
     return _cookieManagerChannel
@@ -122,6 +127,7 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
     _addIfNonNull('jsMode', settings.javascriptMode?.index);
     _addIfNonNull('hasNavigationDelegate', settings.hasNavigationDelegate);
     _addIfNonNull('debuggingEnabled', settings.debuggingEnabled);
+    _addIfNonNull('userAgent', settings.userAgent);
     return map;
   }
 
@@ -135,6 +141,7 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
       'initialUrl': creationParams.initialUrl,
       'settings': _webSettingsToMap(creationParams.webSettings),
       'javascriptChannelNames': creationParams.javascriptChannelNames.toList(),
+      'userAgent': creationParams.userAgent,
     };
   }
 }

packages/webview_flutter/lib/webview_flutter.dart

@@ -121,6 +121,7 @@ class WebView extends StatefulWidget {
     this.gestureRecognizers,
     this.onPageFinished,
     this.debuggingEnabled = false,
+    this.userAgent,
   })  : assert(javascriptMode != null),
         super(key: key);
 
@@ -255,6 +256,18 @@ class WebView extends StatefulWidget {
   /// By default `debuggingEnabled` is false.
   final bool debuggingEnabled;
 
+  /// The User_Agent used for WebView requests.
+  ///
+  /// By default `userAgent` is null.
+  /// If the `userAgent` is null, the default User Agent from the Android / iOS WebView is used.
+  /// WebView User Agent for Android (https://developer.chrome.com/multidevice/user-agent)
+  ///
+  /// When the WebView is rebuild with a new User Agent, the page reloads and the request uses the new User Agent.
+  ///
+  /// When [WebViewController.goBack] is called after changing the User Agent, the old User Agent is used.
+  /// Only after reloading the Page you went back to,the request uses the new User Agent.
+  final String userAgent;
+
   @override
   State<StatefulWidget> createState() => _WebViewState();
 }
@@ -317,6 +330,7 @@ CreationParams _creationParamsfromWidget(WebView widget) {
     initialUrl: widget.initialUrl,
     webSettings: _webSettingsFromWidget(widget),
     javascriptChannelNames: _extractChannelNames(widget.javascriptChannels),
+    userAgent: widget.userAgent,
   );
 }
 
@@ -325,10 +339,11 @@ WebSettings _webSettingsFromWidget(WebView widget) {
     javascriptMode: widget.javascriptMode,
     hasNavigationDelegate: widget.navigationDelegate != null,
     debuggingEnabled: widget.debuggingEnabled,
+    userAgent: widget.userAgent,
   );
 }
 
-// This method assumes that no fields in `currentValue` are null.
+// This method assumes that no fields, except userAgent (see WebView.userAgent), in `currentValue` are null.
 WebSettings _clearUnchangedWebSettings(
     WebSettings currentValue, WebSettings newValue) {
   assert(currentValue.javascriptMode != null);
@@ -340,6 +355,7 @@ WebSettings _clearUnchangedWebSettings(
   JavascriptMode javascriptMode;
   bool hasNavigationDelegate;
   bool debuggingEnabled;
+  String userAgent;
   if (currentValue.javascriptMode != newValue.javascriptMode) {
     javascriptMode = newValue.javascriptMode;
   }
@@ -349,11 +365,15 @@ WebSettings _clearUnchangedWebSettings(
   if (currentValue.debuggingEnabled != newValue.debuggingEnabled) {
     debuggingEnabled = newValue.debuggingEnabled;
   }
+  if (currentValue.userAgent != newValue.userAgent) {
+    userAgent = newValue.userAgent;
+  }
 
   return WebSettings(
       javascriptMode: javascriptMode,
       hasNavigationDelegate: hasNavigationDelegate,
-      debuggingEnabled: debuggingEnabled);
+      debuggingEnabled: debuggingEnabled,
+      userAgent: userAgent);
 }
 
 Set<String> _extractChannelNames(Set<JavascriptChannel> channels) {
@@ -568,6 +588,11 @@ class WebViewController {
     // ignore: strong_mode_implicit_dynamic_method
     return _webViewPlatformController.evaluateJavascript(javascriptString);
   }
+
+  /// Returns the User Agent value that will be used for subsequent HTTP requests.
+  Future<String> getUserAgent() async {
+    return _webViewPlatformController.getUserAgent();
+  }
 }
 
 /// Manages cookies pertaining to all [WebView]s.