Feature/web view failure listener

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

@@ -9,9 +9,13 @@
 import android.os.Build;
 import android.util.Log;
 import android.view.KeyEvent;
+import android.webkit.WebResourceError;
 import android.webkit.WebResourceRequest;
+import android.webkit.WebResourceResponse;
 import android.webkit.WebView;
 import android.webkit.WebViewClient;
+import androidx.annotation.NonNull;
+import androidx.webkit.WebResourceErrorCompat;
 import androidx.webkit.WebViewClientCompat;
 import io.flutter.plugin.common.MethodChannel;
 import java.util.HashMap;
@@ -92,6 +96,14 @@ private void notifyOnNavigationRequest(
     }
   }
 
+  private void onReceiveError(WebView view, int code, String description, String url) {
+    Map<String, Object> args = new HashMap<>();
+    args.put("url", url);
+    args.put("code", code);
+    args.put("description", description);
+    methodChannel.invokeMethod("onPageReceiveError", args);
+  }
+
   // This method attempts to avoid using WebViewClientCompat due to bug
   // https://bugs.chromium.org/p/chromium/issues/detail?id=925887. Also, see
   // https://github.com/flutter/flutter/issues/29446.
@@ -129,6 +141,32 @@ public void onUnhandledKeyEvent(WebView view, KeyEvent event) {
         // handled even though they were handled. We don't want to propagate those as they're not
         // truly lost.
       }
+
+      @TargetApi(Build.VERSION_CODES.M)
+      @Override
+      public void onReceivedError(
+          WebView view, WebResourceRequest request, WebResourceError error) {
+        FlutterWebViewClient.this.onReceiveError(
+            view,
+            error.getErrorCode(),
+            error.getDescription().toString(),
+            request.getUrl().toString());
+      }
+
+      @TargetApi(Build.VERSION_CODES.M)
+      @Override
+      public void onReceivedHttpError(
+          WebView view, WebResourceRequest request, WebResourceResponse errorResponse) {
+        FlutterWebViewClient.this.onReceiveError(
+            view, errorResponse.getStatusCode(), null, request.getUrl().toString());
+      }
+
+      @SuppressWarnings("deprecation")
+      @Override
+      public void onReceivedError(
+          WebView view, int errorCode, String description, String failingUrl) {
+        FlutterWebViewClient.this.onReceiveError(view, errorCode, description, failingUrl);
+      }
     };
   }
 
@@ -160,6 +198,37 @@ public void onUnhandledKeyEvent(WebView view, KeyEvent event) {
         // handled even though they were handled. We don't want to propagate those as they're not
         // truly lost.
       }
+
+      @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+      @Override
+      public void onReceivedHttpError(
+          @NonNull WebView view,
+          @NonNull WebResourceRequest request,
+          @NonNull WebResourceResponse errorResponse) {
+        FlutterWebViewClient.this.onReceiveError(
+            view, errorResponse.getStatusCode(), null, request.getUrl().toString());
+      }
+
+      @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+      @Override
+      public void onReceivedError(
+          @NonNull WebView view,
+          @NonNull WebResourceRequest request,
+          @NonNull WebResourceErrorCompat error) {
+        //TODO: is really need to check WebViewFeature.isFeatureSupported() and api version.
+        FlutterWebViewClient.this.onReceiveError(
+            view,
+            error.getErrorCode(),
+            error.getDescription().toString(),
+            request.getUrl().toString());
+      }
+
+      @SuppressWarnings("deprecation")
+      @Override
+      public void onReceivedError(
+          WebView view, int errorCode, String description, String failingUrl) {
+        FlutterWebViewClient.this.onReceiveError(view, errorCode, description, failingUrl);
+      }
     };
   }
 

packages/webview_flutter/example/lib/main.dart

@@ -50,7 +50,7 @@ class _WebViewExampleState extends State<WebViewExample> {
       // to allow calling Scaffold.of(context) so we can show a snackbar.
       body: Builder(builder: (BuildContext context) {
         return WebView(
-          initialUrl: 'https://flutter.dev',
+          initialUrl: 'https://google.com',
           javascriptMode: JavascriptMode.unrestricted,
           onWebViewCreated: (WebViewController webViewController) {
             _controller.complete(webViewController);
@@ -74,6 +74,13 @@ class _WebViewExampleState extends State<WebViewExample> {
           onPageFinished: (String url) {
             print('Page finished loading: $url');
           },
+          onPageReceiveError: (String url, int code, String message) {
+            Scaffold.of(context).showSnackBar(SnackBar(
+              content: Text(
+                'Code: $code, Url: $url, Message: $message',
+              ),
+            ));
+          },
           gestureNavigationEnabled: true,
         );
       }),

packages/webview_flutter/ios/Classes/FLTWKNavigationDelegate.m

@@ -5,10 +5,10 @@
 #import "FLTWKNavigationDelegate.h"
 
 @implementation FLTWKNavigationDelegate {
-  FlutterMethodChannel* _methodChannel;
+  FlutterMethodChannel *_methodChannel;
 }
 
-- (instancetype)initWithChannel:(FlutterMethodChannel*)channel {
+- (instancetype)initWithChannel:(FlutterMethodChannel *)channel {
   self = [super init];
   if (self) {
     _methodChannel = channel;
@@ -18,26 +18,27 @@ - (instancetype)initWithChannel:(FlutterMethodChannel*)channel {
 
 #pragma mark - WKNavigationDelegate conformance
 
-- (void)webView:(WKWebView*)webView didStartProvisionalNavigation:(WKNavigation*)navigation {
+- (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(WKNavigation *)navigation {
   [_methodChannel invokeMethod:@"onPageStarted" arguments:@{@"url" : webView.URL.absoluteString}];
 }
 
-- (void)webView:(WKWebView*)webView
-    decidePolicyForNavigationAction:(WKNavigationAction*)navigationAction
+- (void)webView:(WKWebView *)webView
+    decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction
                     decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler {
   if (!self.hasDartNavigationDelegate) {
     decisionHandler(WKNavigationActionPolicyAllow);
     return;
   }
-  NSDictionary* arguments = @{
+  NSDictionary *arguments = @{
     @"url" : navigationAction.request.URL.absoluteString,
     @"isForMainFrame" : @(navigationAction.targetFrame.isMainFrame)
   };
   [_methodChannel invokeMethod:@"navigationRequest"
                      arguments:arguments
                         result:^(id _Nullable result) {
                           if ([result isKindOfClass:[FlutterError class]]) {
-                            NSLog(@"navigationRequest has unexpectedly completed with an error, "
+                            NSLog(@"navigationRequest has unexpectedly completed with an "
+                                  @"error, "
                                   @"allowing navigation.");
                             decisionHandler(WKNavigationActionPolicyAllow);
                             return;
@@ -50,19 +51,64 @@ - (void)webView:(WKWebView*)webView
                             return;
                           }
                           if (![result isKindOfClass:[NSNumber class]]) {
-                            NSLog(@"navigationRequest unexpectedly returned a non boolean value: "
+                            NSLog(@"navigationRequest unexpectedly returned a non boolean "
+                                  @"value: "
                                   @"%@, allowing navigation.",
                                   result);
                             decisionHandler(WKNavigationActionPolicyAllow);
                             return;
                           }
-                          NSNumber* typedResult = result;
+                          NSNumber *typedResult = result;
                           decisionHandler([typedResult boolValue] ? WKNavigationActionPolicyAllow
                                                                   : WKNavigationActionPolicyCancel);
                         }];
 }
 
-- (void)webView:(WKWebView*)webView didFinishNavigation:(WKNavigation*)navigation {
+- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation {
   [_methodChannel invokeMethod:@"onPageFinished" arguments:@{@"url" : webView.URL.absoluteString}];
 }
+
+- (void)webView:(WKWebView *)webView
+    didFailNavigation:(WKNavigation *)navigation
+            withError:(NSError *)error {
+  NSDictionary *arguments = @{
+    @"url" : webView.URL.absoluteString ?: [NSNull null],
+    @"code" : [NSNumber numberWithLong:error.code],
+    @"description" : [error localizedDescription],
+  };
+
+  [_methodChannel invokeMethod:@"onPageReceiveError" arguments:arguments];
+}
+
+- (void)webView:(WKWebView *)webView
+    didFailProvisionalNavigation:(WKNavigation *)navigation
+                       withError:(NSError *)error {
+  NSDictionary *arguments = @{
+    @"url" : error.userInfo[NSURLErrorFailingURLStringErrorKey],
+    @"code" : [NSNumber numberWithLong:error.code],
+    @"description" : [error localizedDescription],
+  };
+
+  [_methodChannel invokeMethod:@"onPageReceiveError" arguments:arguments];
+}
+
+- (void)webView:(WKWebView *)webView
+    decidePolicyForNavigationResponse:(WKNavigationResponse *)navigationResponse
+                      decisionHandler:(void (^)(WKNavigationResponsePolicy))decisionHandler {
+  if ([navigationResponse.response isKindOfClass:[NSHTTPURLResponse class]]) {
+    NSHTTPURLResponse *response = (NSHTTPURLResponse *)navigationResponse.response;
+    if (response.statusCode >= 400 && response.statusCode < 600) {
+      NSDictionary *arguments = @{
+        @"url" : response.URL.absoluteString ?: [NSNull null],
+        @"code" : [NSNumber numberWithLong:response.statusCode],
+        @"description" : [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode],
+      };
+
+      [_methodChannel invokeMethod:@"onPageReceiveError" arguments:arguments];
+    }
+  }
+
+  decisionHandler(WKNavigationResponsePolicyAllow);
+}
+
 @end

packages/webview_flutter/lib/platform_interface.dart

@@ -28,6 +28,9 @@ abstract class WebViewPlatformCallbacksHandler {
 
   /// Invoked by [WebViewPlatformController] when a page has finished loading.
   void onPageFinished(String url);
+
+  /// Invoked by [WebViewPlatformController] when platform's webview return error.
+  void onPageReceiveError({String url, int code, String description});
 }
 
 /// Interface for talking to the webview's platform implementation.

packages/webview_flutter/lib/src/webview_method_channel.dart

@@ -43,6 +43,12 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
       case 'onPageStarted':
         _platformCallbacksHandler.onPageStarted(call.arguments['url']);
         return null;
+      case 'onPageReceiveError':
+        _platformCallbacksHandler.onPageReceiveError(
+            url: call.arguments['url'],
+            code: call.arguments['code'],
+            description: call.arguments['description']);
+        return null;
     }
     throw MissingPluginException(
         '${call.method} was invoked but has no handler');

packages/webview_flutter/lib/webview_flutter.dart

@@ -79,6 +79,13 @@ typedef void PageStartedCallback(String url);
 /// Signature for when a [WebView] has finished loading a page.
 typedef void PageFinishedCallback(String url);
 
+/// Signature for when a [WebView] receive a error.
+/// Code may be NSURLErrorDomain code or const from Android WebViewClient or http status code.
+/// Description is optional
+typedef void PageReceiveErrorCallback(String url, int code, String description);
+
+final RegExp _validChannelNames = RegExp('^[a-zA-Z_][a-zA-Z0-9_]*\$');
+
 /// Specifies possible restrictions on automatic media playback.
 ///
 /// This is typically used in [WebView.initialMediaPlaybackPolicy].
@@ -98,8 +105,6 @@ enum AutoMediaPlaybackPolicy {
   always_allow,
 }
 
-final RegExp _validChannelNames = RegExp('^[a-zA-Z_][a-zA-Z0-9_]*\$');
-
 /// A named channel for receiving messaged from JavaScript code running inside a web view.
 class JavascriptChannel {
   /// Constructs a Javascript channel.
@@ -152,6 +157,7 @@ class WebView extends StatefulWidget {
     this.userAgent,
     this.initialMediaPlaybackPolicy =
         AutoMediaPlaybackPolicy.require_user_action_for_all_media_types,
+    this.onPageReceiveError,
   })  : assert(javascriptMode != null),
         assert(initialMediaPlaybackPolicy != null),
         super(key: key);
@@ -290,6 +296,9 @@ class WebView extends StatefulWidget {
   /// By default `debuggingEnabled` is false.
   final bool debuggingEnabled;
 
+  /// Invoked when a webview return error.
+  final PageReceiveErrorCallback onPageReceiveError;
+
   /// The value used for the HTTP User-Agent: request header.
   /// A Boolean value indicating whether horizontal swipe gestures will trigger back-forward list navigations.
   ///
@@ -482,6 +491,13 @@ class _PlatformCallbacksHandler implements WebViewPlatformCallbacksHandler {
     }
   }
 
+  @override
+  void onPageReceiveError({String url, int code, String description}) {
+    if (_widget.onPageReceiveError != null) {
+      _widget.onPageReceiveError(url, code, description);
+    }
+  }
+
   void _updateJavascriptChannelsFromSet(Set<JavascriptChannel> channels) {
     _javascriptChannels.clear();
     if (channels == null) {