[webview_flutter] Support loading data directly in WebView via loadData and loadDataBase64

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

@@ -174,6 +174,12 @@ public void onMethodCall(MethodCall methodCall, Result result) {
       case "loadUrl":
         loadUrl(methodCall, result);
         break;
+      case "loadData":
+        loadData(methodCall, result);
+        break;
+      case "loadDataBase64":
+        loadDataBase64(methodCall, result);
+        break;
       case "updateSettings":
         updateSettings(methodCall, result);
         break;
@@ -239,6 +245,33 @@ private void loadUrl(MethodCall methodCall, Result result) {
     result.success(null);
   }
 
+  @SuppressWarnings("unchecked")
+  private void loadData(MethodCall methodCall, Result result) {
+    Map<String, Object> request = (Map<String, Object>) methodCall.arguments;
+    String baseUrl = (String) request.get("baseUrl");
+    String data = (String) request.get("data");
+    String mimeType = (String) request.get("mimeType");
+
+    final String encoding = "UTF-8";
+    webView.loadDataWithBaseURL(baseUrl, data, mimeType, encoding, null);
+    result.success(null);
+  }
+
+  @SuppressWarnings("unchecked")
+  private void loadDataBase64(MethodCall methodCall, Result result) {
+    Map<String, Object> request = (Map<String, Object>) methodCall.arguments;
+    String data = (String) request.get("data");
+    String mimeType = (String) request.get("mimeType");
+
+    // We do not use baseUrl, because Android has no way to set it in this context.
+
+    // Theoretically, we should be able to use WebView#loadDataWithBaseURL here, but
+    // support for base64 seems to be broken.
+    final String url = String.format("data:%s;base64,%s", mimeType, data);
+    webView.loadUrl(url);
+    result.success(null);
+  }
+
   private void canGoBack(Result result) {
     result.success(webView.canGoBack());
   }

packages/webview_flutter/ios/Classes/FlutterWebView.m

@@ -128,6 +128,10 @@ - (void)onMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
     [self onUpdateSettings:call result:result];
   } else if ([[call method] isEqualToString:@"loadUrl"]) {
     [self onLoadUrl:call result:result];
+  } else if ([[call method] isEqualToString:@"loadData"]) {
+    [self onLoadData:call result:result];
+  } else if ([[call method] isEqualToString:@"loadDataBase64"]) {
+    [self onLoadDataBase64:call result:result];
   } else if ([[call method] isEqualToString:@"canGoBack"]) {
     [self onCanGoBack:call result:result];
   } else if ([[call method] isEqualToString:@"canGoForward"]) {
@@ -183,6 +187,112 @@ - (void)onLoadUrl:(FlutterMethodCall*)call result:(FlutterResult)result {
   }
 }
 
+- (void)onLoadData:(FlutterMethodCall*)call result:(FlutterResult)result {
+  NSDictionary<NSString*, id>* arguments = [call arguments];
+  if (!arguments) {
+    result([FlutterError errorWithCode:@"loadData_failed"
+                               message:@"No arguments passed to method"
+                               details:nil]);
+    return;
+  }
+
+  NSString* const encoding = @"UTF-8";
+  NSString* mimeType = arguments[@"mimeType"];
+  NSString* baseUrl = arguments[@"baseUrl"];
+  NSString* dataStr = arguments[@"data"];
+
+  if (![mimeType isKindOfClass:[NSString class]]) {
+    result([FlutterError errorWithCode:@"loadData_failed"
+                               message:@"Argument type of mimeType is not string"
+                               details:nil]);
+    return;
+  }
+
+  if (![baseUrl isKindOfClass:[NSString class]]) {
+    result([FlutterError errorWithCode:@"loadData_failed"
+                               message:@"Argument type of baseUrl is not string"
+                               details:nil]);
+    return;
+  }
+
+  NSURL* nsUrl = [NSURL URLWithString:baseUrl];
+  if (!nsUrl) {
+    result([FlutterError errorWithCode:@"loadData_failed"
+                               message:@"Argument type of baseUrl is not a valid URL"
+                               details:[NSString stringWithFormat:@"URL was: '%@'", baseUrl]]);
+    return;
+  }
+
+  if (![dataStr isKindOfClass:[NSString class]]) {
+    result([FlutterError errorWithCode:@"loadData_failed"
+                               message:@"Argument type of data is not string"
+                               details:nil]);
+    return;
+  }
+
+  NSData* data = [dataStr dataUsingEncoding:NSUTF8StringEncoding];
+  if (@available(iOS 9.0, *)) {
+    [_webView loadData:data MIMEType:mimeType characterEncodingName:encoding baseURL:nsUrl];
+  } else {
+    NSLog(@"Setting data is not supported for Flutter WebViews prior to iOS 9.");
+  }
+
+  result(nil);
+}
+
+- (void)onLoadDataBase64:(FlutterMethodCall*)call result:(FlutterResult)result {
+  NSDictionary<NSString*, id>* arguments = [call arguments];
+  if (!arguments) {
+    result([FlutterError errorWithCode:@"loadDataBase64_failed"
+                               message:@"No arguments passed to method"
+                               details:nil]);
+    return;
+  }
+
+  NSString* const encoding = @"UTF-8";
+  NSString* mimeType = arguments[@"mimeType"];
+  NSString* dataStr = arguments[@"data"];
+  NSString* baseUrl = arguments[@"baseUrl"];
+
+  if (![mimeType isKindOfClass:[NSString class]]) {
+    result([FlutterError errorWithCode:@"loadDataBase64_failed"
+                               message:@"Argument type of mimeType is not string"
+                               details:nil]);
+    return;
+  }
+
+  if (![dataStr isKindOfClass:[NSString class]]) {
+    result([FlutterError errorWithCode:@"loadDataBase64_failed"
+                               message:@"Argument type of data is not string"
+                               details:nil]);
+    return;
+  }
+
+  if (![baseUrl isKindOfClass:[NSString class]]) {
+    result([FlutterError errorWithCode:@"loadDataBase64_failed"
+                               message:@"Argument type of baseUrl is not string"
+                               details:nil]);
+    return;
+  }
+
+  NSURL* nsUrl = [NSURL URLWithString:baseUrl];
+  if (!nsUrl) {
+    result([FlutterError errorWithCode:@"loadData_failed"
+                               message:@"Argument type of baseUrl is not a valid URL"
+                               details:[NSString stringWithFormat:@"URL was: '%@'", baseUrl]]);
+    return;
+  }
+
+  NSData* data = [[NSData alloc] initWithBase64EncodedString:dataStr options:0];
+  if (@available(iOS 9.0, *)) {
+    [_webView loadData:data MIMEType:mimeType characterEncodingName:encoding baseURL:nsUrl];
+  } else {
+    NSLog(@"Setting data is not supported for Flutter WebViews prior to iOS 9.");
+  }
+
+  result(nil);
+}
+
 - (void)onCanGoBack:(FlutterMethodCall*)call result:(FlutterResult)result {
   BOOL canGoBack = [_webView canGoBack];
   result([NSNumber numberWithBool:canGoBack]);

packages/webview_flutter/lib/platform_interface.dart

@@ -182,6 +182,41 @@ abstract class WebViewPlatformController {
         "WebView loadUrl is not implemented on the current platform");
   }
 
+  /// Loads the specified content data into the WebView.
+  ///
+  /// The string `data` will be interpreted as a UTF-8 string.
+  ///
+  /// `baseUrl` is the apparent URL which the page was loaded at, used to resolve
+  /// relative paths.
+  ///
+  /// Throws an ArgumentError if `baseUrl` is not a valid URL string.
+  Future<void> loadData(
+    String data,
+    String baseUrl,
+    String mimeType,
+  ) {
+    throw UnimplementedError(
+        "WebView loadData is not implemented on the current platform");
+  }
+
+  /// Loads the specified content data into the WebView.
+  ///
+  /// The string `data` will be interpreted as a Base64 encoded string. Note
+  /// that any trailing padding = or == characters MUST be present for full device
+  /// compatibility.
+  ///
+  /// The `baseUrl` argument is required but has no effect on Android.
+  ///
+  /// Throws an ArgumentError if `baseUrl` is not a valid URL string.
+  Future<void> loadDataBase64(
+    String data,
+    String mimeType,
+    String baseUrl,
+  ) {
+    throw UnimplementedError(
+        "WebView loadDataBase64 is not implemented on the current platform");
+  }
+
   /// Updates the webview settings.
   ///
   /// Any non null field in `settings` will be set as the new setting value.

packages/webview_flutter/lib/src/webview_method_channel.dart

@@ -80,6 +80,38 @@ class MethodChannelWebViewPlatform implements WebViewPlatformController {
     });
   }
 
+  @override
+  Future<void> loadData(
+    String data,
+    String baseUrl,
+    String mimeType,
+  ) async {
+    assert(data != null);
+    assert(baseUrl != null);
+    assert(mimeType != null);
+    return _channel.invokeMethod<void>('loadData', <String, dynamic>{
+      'data': data,
+      'baseUrl': baseUrl,
+      'mimeType': mimeType,
+    });
+  }
+
+  @override
+  Future<void> loadDataBase64(
+    String data,
+    String mimeType,
+    String baseUrl,
+  ) async {
+    assert(data != null);
+    assert(mimeType != null);
+    assert(baseUrl != null);
+    return _channel.invokeMethod<void>('loadDataBase64', <String, dynamic>{
+      'data': data,
+      'mimeType': mimeType,
+      'baseUrl': baseUrl,
+    });
+  }
+
   @override
   Future<String> currentUrl() => _channel.invokeMethod<String>('currentUrl');
 

packages/webview_flutter/lib/webview_flutter.dart

@@ -609,6 +609,45 @@ class WebViewController {
     return _webViewPlatformController.loadUrl(url, headers);
   }
 
+  /// Loads the specified content data into the WebView.
+  ///
+  /// The string `data` will be interpreted as a UTF-8 string.
+  ///
+  /// `baseUrl` is the apparent URL which the page was loaded at, used to resolve
+  /// relative paths.
+  ///
+  /// Throws an ArgumentError if `baseUrl` is not a valid URL string.
+  Future<void> loadData(
+    String data, {
+    @required String baseUrl,
+    @required String mimeType,
+  }) async {
+    assert(data != null);
+    assert(baseUrl != null);
+    assert(mimeType != null);
+    _validateUrlString(baseUrl);
+    return _webViewPlatformController.loadData(data, baseUrl, mimeType);
+  }
+
+  /// Loads the specified content data into the WebView.
+  ///
+  /// The string `data` will be interpreted as a Base64 encoded string. Note
+  /// that any trailing padding = or == characters MUST be present for full device
+  /// compatibility.
+  ///
+  /// The `baseUrl` argument is required but has no effect on Android.
+  ///
+  /// Throws an ArgumentError if `baseUrl` is not a valid URL string.
+  Future<void> loadDataBase64(
+    String data, {
+    @required String mimeType,
+    @required String baseUrl,
+  }) async {
+    assert(data != null);
+    assert(mimeType != null);
+    return _webViewPlatformController.loadDataBase64(data, mimeType, baseUrl);
+  }
+
   /// Accessor to the current URL that the WebView is displaying.
   ///
   /// If [WebView.initialUrl] was never specified, returns `null`.