[webview_flutter] Support for loading progress tracking (flutter#2151)

packages/webview_flutter/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.0.0-nullsafety.6
+
+* Added support for progress tracking.
+
 ## 2.0.0-nullsafety.5
 
 * Add section to the wiki explaining how to use Material components.

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

@@ -72,6 +72,11 @@ public boolean shouldOverrideUrlLoading(WebView view, String url) {
 
       return true;
     }
+
+    @Override
+    public void onProgressChanged(WebView view, int progress) {
+      flutterWebViewClient.onLoadingProgress(progress);
+    }
   }
 
   @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
@@ -367,6 +372,9 @@ private void applySettings(Map<String, Object> settings) {
             webView.setWebContentsDebuggingEnabled(debuggingEnabled);
           }
           break;
+        case "hasProgressTracking":
+          flutterWebViewClient.hasProgressTracking = (boolean) settings.get(key);
+          break;
         case "gestureNavigationEnabled":
           break;
         case "userAgent":

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

@@ -30,6 +30,7 @@ class FlutterWebViewClient {
   private static final String TAG = "FlutterWebViewClient";
   private final MethodChannel methodChannel;
   private boolean hasNavigationDelegate;
+  boolean hasProgressTracking;
 
   FlutterWebViewClient(MethodChannel methodChannel) {
     this.methodChannel = methodChannel;
@@ -125,6 +126,14 @@ private void onPageFinished(WebView view, String url) {
     methodChannel.invokeMethod("onPageFinished", args);
   }
 
+  void onLoadingProgress(int progress) {
+    if (hasProgressTracking) {
+      Map<String, Object> args = new HashMap<>();
+      args.put("progress", progress);
+      methodChannel.invokeMethod("onProgress", args);
+    }
+  }
+
   private void onWebResourceError(
       final int errorCode, final String description, final String failingUrl) {
     final Map<String, Object> args = new HashMap<>();

packages/webview_flutter/example/lib/main.dart

@@ -62,6 +62,9 @@ class _WebViewExampleState extends State<WebViewExample> {
           onWebViewCreated: (WebViewController webViewController) {
             _controller.complete(webViewController);
           },
+          onProgress: (int progress) {
+            print("WebView is loading (progress : $progress%)");
+          },
           javascriptChannels: <JavascriptChannel>{
             _toasterJavascriptChannel(context),
           },

packages/webview_flutter/ios/Classes/FLTWKProgressionDelegate.h

@@ -0,0 +1,19 @@
+// Copyright 2019 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 <Flutter/Flutter.h>
+#import <Foundation/Foundation.h>
+#import <WebKit/WebKit.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface FLTWKProgressionDelegate : NSObject
+
+- (instancetype)initWithWebView:(WKWebView *)webView channel:(FlutterMethodChannel *)channel;
+
+- (void)stopObservingProgress:(WKWebView *)webView;
+
+@end
+
+NS_ASSUME_NONNULL_END

packages/webview_flutter/ios/Classes/FLTWKProgressionDelegate.m

@@ -0,0 +1,42 @@
+// Copyright 2019 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 "FLTWKProgressionDelegate.h"
+
+NSString *const FLTWKEstimatedProgressKeyPath = @"estimatedProgress";
+
+@implementation FLTWKProgressionDelegate {
+  FlutterMethodChannel *_methodChannel;
+}
+
+- (instancetype)initWithWebView:(WKWebView *)webView channel:(FlutterMethodChannel *)channel {
+  self = [super init];
+  if (self) {
+    _methodChannel = channel;
+    [webView addObserver:self
+              forKeyPath:FLTWKEstimatedProgressKeyPath
+                 options:NSKeyValueObservingOptionNew
+                 context:nil];
+  }
+  return self;
+}
+
+- (void)stopObservingProgress:(WKWebView *)webView {
+  [webView removeObserver:self forKeyPath:FLTWKEstimatedProgressKeyPath];
+}
+
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary<NSKeyValueChangeKey, id> *)change
+                       context:(void *)context {
+  if ([keyPath isEqualToString:FLTWKEstimatedProgressKeyPath]) {
+    NSNumber *newValue =
+        change[NSKeyValueChangeNewKey] ?: 0;          // newValue is anywhere between 0.0 and 1.0
+    int newValueAsInt = [newValue floatValue] * 100;  // Anywhere between 0 and 100
+    [_methodChannel invokeMethod:@"onProgress"
+                       arguments:@{@"progress" : [NSNumber numberWithInt:newValueAsInt]}];
+  }
+}
+
+@end

packages/webview_flutter/ios/Classes/FlutterWebView.m

@@ -4,6 +4,7 @@
 
 #import "FlutterWebView.h"
 #import "FLTWKNavigationDelegate.h"
+#import "FLTWKProgressionDelegate.h"
 #import "JavaScriptChannelHandler.h"
 
 @implementation FLTWebViewFactory {
@@ -64,6 +65,7 @@ @implementation FLTWebViewController {
   // The set of registered JavaScript channel names.
   NSMutableSet* _javaScriptChannelNames;
   FLTWKNavigationDelegate* _navigationDelegate;
+  FLTWKProgressionDelegate* _progressionDelegate;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame
@@ -119,6 +121,12 @@ - (instancetype)initWithFrame:(CGRect)frame
   return self;
 }
 
+- (void)dealloc {
+  if (_progressionDelegate != nil) {
+    [_progressionDelegate stopObservingProgress:_webView];
+  }
+}
+
 - (UIView*)view {
   return _webView;
 }
@@ -323,6 +331,13 @@ - (NSString*)applySettings:(NSDictionary<NSString*, id>*)settings {
     } else if ([key isEqualToString:@"hasNavigationDelegate"]) {
       NSNumber* hasDartNavigationDelegate = settings[key];
       _navigationDelegate.hasDartNavigationDelegate = [hasDartNavigationDelegate boolValue];
+    } else if ([key isEqualToString:@"hasProgressTracking"]) {
+      NSNumber* hasProgressTrackingValue = settings[key];
+      bool hasProgressTracking = [hasProgressTrackingValue boolValue];
+      if (hasProgressTracking) {
+        _progressionDelegate = [[FLTWKProgressionDelegate alloc] initWithWebView:_webView
+                                                                         channel:_channel];
+      }
     } else if ([key isEqualToString:@"debuggingEnabled"]) {
       // no-op debugging is always enabled on iOS.
     } else if ([key isEqualToString:@"gestureNavigationEnabled"]) {

packages/webview_flutter/lib/platform_interface.dart

@@ -30,6 +30,10 @@ abstract class WebViewPlatformCallbacksHandler {
   /// Invoked by [WebViewPlatformController] when a page has finished loading.
   void onPageFinished(String url);
 
+  /// Invoked by [WebViewPlatformController] when a page is loading.
+  /// /// Only works when [WebSettings.hasProgressTracking] is set to `true`.
+  void onProgress(int progress);
+
   /// Report web resource loading error to the host application.
   void onWebResourceError(WebResourceError error);
 }
@@ -388,6 +392,7 @@ class WebSettings {
   WebSettings({
     this.javascriptMode,
     this.hasNavigationDelegate,
+    this.hasProgressTracking,
     this.debuggingEnabled,
     this.gestureNavigationEnabled,
     this.allowsInlineMediaPlayback,
@@ -400,6 +405,10 @@ class WebSettings {
   /// Whether the [WebView] has a [NavigationDelegate] set.
   final bool? hasNavigationDelegate;
 
+  /// Whether the [WebView] should track page loading progress.
+  /// See also: [WebViewPlatformCallbacksHandler.onProgress] to get the progress.
+  final bool? hasProgressTracking;
+
   /// Whether to enable the platform's webview content debugging tools.
   ///
   /// See also: [WebView.debuggingEnabled].
@@ -427,7 +436,7 @@ class WebSettings {
 
   @override
   String toString() {
-    return 'WebSettings(javascriptMode: $javascriptMode, hasNavigationDelegate: $hasNavigationDelegate, debuggingEnabled: $debuggingEnabled, gestureNavigationEnabled: $gestureNavigationEnabled, userAgent: $userAgent, allowsInlineMediaPlayback: $allowsInlineMediaPlayback)';
+    return 'WebSettings(javascriptMode: $javascriptMode, hasNavigationDelegate: $hasNavigationDelegate, hasProgressTracking: $hasProgressTracking, debuggingEnabled: $debuggingEnabled, gestureNavigationEnabled: $gestureNavigationEnabled, userAgent: $userAgent, allowsInlineMediaPlayback: $allowsInlineMediaPlayback)';
   }
 }
 

packages/webview_flutter/lib/src/webview_method_channel.dart

@@ -40,6 +40,9 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
       case 'onPageFinished':
         _platformCallbacksHandler.onPageFinished(call.arguments['url']!);
         return null;
+      case 'onProgress':
+        _platformCallbacksHandler.onProgress(call.arguments['progress']);
+        return null;
       case 'onPageStarted':
         _platformCallbacksHandler.onPageStarted(call.arguments['url']!);
         return null;
@@ -183,6 +186,7 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
 
     _addIfNonNull('jsMode', settings!.javascriptMode?.index);
     _addIfNonNull('hasNavigationDelegate', settings.hasNavigationDelegate);
+    _addIfNonNull('hasProgressTracking', settings.hasProgressTracking);
     _addIfNonNull('debuggingEnabled', settings.debuggingEnabled);
     _addIfNonNull(
         'gestureNavigationEnabled', settings.gestureNavigationEnabled);

packages/webview_flutter/lib/webview_flutter.dart

@@ -142,6 +142,9 @@ 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] is loading a page.
+typedef void PageLoadingCallback(int progress);
+
 /// Signature for when a [WebView] has failed to load a resource.
 typedef void WebResourceErrorCallback(WebResourceError error);
 
@@ -217,6 +220,7 @@ class WebView extends StatefulWidget {
     this.gestureRecognizers,
     this.onPageStarted,
     this.onPageFinished,
+    this.onProgress,
     this.onWebResourceError,
     this.debuggingEnabled = false,
     this.gestureNavigationEnabled = false,
@@ -357,6 +361,9 @@ class WebView extends StatefulWidget {
   /// [WebViewController.evaluateJavascript] can assume this.
   final PageFinishedCallback? onPageFinished;
 
+  /// Invoked when a page is loading.
+  final PageLoadingCallback? onProgress;
+
   /// Invoked when a web resource has failed to load.
   ///
   /// This can be called for any resource (iframe, image, etc.), not just for
@@ -476,6 +483,7 @@ WebSettings _webSettingsFromWidget(WebView widget) {
   return WebSettings(
     javascriptMode: widget.javascriptMode,
     hasNavigationDelegate: widget.navigationDelegate != null,
+    hasProgressTracking: widget.onProgress != null,
     debuggingEnabled: widget.debuggingEnabled,
     gestureNavigationEnabled: widget.gestureNavigationEnabled,
     allowsInlineMediaPlayback: widget.allowsInlineMediaPlayback,
@@ -488,6 +496,7 @@ WebSettings _clearUnchangedWebSettings(
     WebSettings currentValue, WebSettings newValue) {
   assert(currentValue.javascriptMode != null);
   assert(currentValue.hasNavigationDelegate != null);
+  assert(currentValue.hasProgressTracking != null);
   assert(currentValue.debuggingEnabled != null);
   assert(currentValue.userAgent != null);
   assert(newValue.javascriptMode != null);
@@ -497,6 +506,7 @@ WebSettings _clearUnchangedWebSettings(
 
   JavascriptMode? javascriptMode;
   bool? hasNavigationDelegate;
+  bool? hasProgressTracking;
   bool? debuggingEnabled;
   WebSetting<String?> userAgent = WebSetting.absent();
   if (currentValue.javascriptMode != newValue.javascriptMode) {
@@ -505,6 +515,9 @@ WebSettings _clearUnchangedWebSettings(
   if (currentValue.hasNavigationDelegate != newValue.hasNavigationDelegate) {
     hasNavigationDelegate = newValue.hasNavigationDelegate;
   }
+  if (currentValue.hasProgressTracking != newValue.hasProgressTracking) {
+    hasProgressTracking = newValue.hasProgressTracking;
+  }
   if (currentValue.debuggingEnabled != newValue.debuggingEnabled) {
     debuggingEnabled = newValue.debuggingEnabled;
   }
@@ -515,6 +528,7 @@ WebSettings _clearUnchangedWebSettings(
   return WebSettings(
     javascriptMode: javascriptMode,
     hasNavigationDelegate: hasNavigationDelegate,
+    hasProgressTracking: hasProgressTracking,
     debuggingEnabled: debuggingEnabled,
     userAgent: userAgent,
   );
@@ -571,6 +585,12 @@ class _PlatformCallbacksHandler implements WebViewPlatformCallbacksHandler {
   }
 
   @override
+  void onProgress(int progress) {
+    if (_widget.onProgress != null) {
+      _widget.onProgress!(progress);
+    }
+  }
+
   void onWebResourceError(WebResourceError error) {
     if (_widget.onWebResourceError != null) {
       _widget.onWebResourceError!(error);

packages/webview_flutter/test/webview_flutter_test.dart

@@ -692,6 +692,62 @@ void main() {
     });
   });
 
+  group('$PageLoadingCallback', () {
+    testWidgets('onLoadingProgress is not null', (WidgetTester tester) async {
+      int? loadingProgress;
+
+      await tester.pumpWidget(WebView(
+        initialUrl: 'https://youtube.com',
+        onProgress: (int progress) {
+          loadingProgress = progress;
+        },
+      ));
+
+      final FakePlatformWebView? platformWebView =
+          fakePlatformViewsController.lastCreatedView;
+
+      platformWebView?.fakeOnProgressCallback(50);
+
+      expect(loadingProgress, 50);
+    });
+
+    testWidgets('onLoadingProgress is null', (WidgetTester tester) async {
+      await tester.pumpWidget(const WebView(
+        initialUrl: 'https://youtube.com',
+        onProgress: null,
+      ));
+
+      final FakePlatformWebView platformWebView =
+          fakePlatformViewsController.lastCreatedView!;
+
+      // This is to test that it does not crash on a null callback.
+      platformWebView.fakeOnProgressCallback(50);
+    });
+
+    testWidgets('onLoadingProgress changed', (WidgetTester tester) async {
+      int? loadingProgress;
+
+      await tester.pumpWidget(WebView(
+        initialUrl: 'https://youtube.com',
+        onProgress: (int progress) {},
+      ));
+
+      await tester.pumpWidget(WebView(
+        initialUrl: 'https://youtube.com',
+        onProgress: (int progress) {
+          loadingProgress = progress;
+        },
+      ));
+
+      final FakePlatformWebView platformWebView =
+          fakePlatformViewsController.lastCreatedView!;
+
+      platformWebView.fakeOnProgressCallback(50);
+
+      expect(loadingProgress, 50);
+    });
+  });
+
   group('navigationDelegate', () {
     testWidgets('hasNavigationDelegate', (WidgetTester tester) async {
       await tester.pumpWidget(const WebView(
@@ -1021,6 +1077,18 @@ class FakePlatformWebView {
     );
   }
 
+  void fakeOnProgressCallback(int progress) {
+    final StandardMethodCodec codec = const StandardMethodCodec();
+
+    final ByteData data = codec.encodeMethodCall(MethodCall(
+      'onProgress',
+      <dynamic, dynamic>{'progress': progress},
+    ));
+
+    ServicesBinding.instance!.defaultBinaryMessenger
+        .handlePlatformMessage(channel.name, data, (ByteData? data) {});
+  }
+
   void _loadUrl(String? url) {
     history = history.sublist(0, currentPosition + 1);
     history.add(url);