Implementation of loadFile for WKWebView.

Adds native implementation for the `loadFile` method channel call to the
webview_flutter_wkwebview package.

packages/webview_flutter/webview_flutter_wkwebview/example/ios/RunnerTests/FLTWebViewTests.m

@@ -88,6 +88,104 @@ - (void)testContentInsetsSumAlwaysZeroAfterSetFrame {
   }
 }
 
+- (void)testLoadFileSucceeds {
+  NSString *testFilePath = @"/assets/file.html";
+  NSURL *url = [NSURL fileURLWithPath:testFilePath isDirectory:NO];
+  XCTestExpectation *resultExpectation =
+      [self expectationWithDescription:@"Should return successful result over the method channel."];
+  FLTWebViewController *controller =
+      [[FLTWebViewController alloc] initWithFrame:CGRectMake(0, 0, 300, 400)
+                                   viewIdentifier:1
+                                        arguments:nil
+                                  binaryMessenger:self.mockBinaryMessenger];
+  FLTWKWebView *mockWebView = OCMClassMock(FLTWKWebView.class);
+  controller.webView = mockWebView;
+  [controller onMethodCall:[FlutterMethodCall methodCallWithMethodName:@"loadFile"
+                                                             arguments:testFilePath]
+                    result:^(id _Nullable result) {
+                      XCTAssertNil(result);
+                      [resultExpectation fulfill];
+                    }];
+
+  [self waitForExpectations:@[ resultExpectation ] timeout:30.0];
+  OCMVerify([mockWebView loadFileURL:url
+             allowingReadAccessToURL:[url URLByDeletingLastPathComponent]]);
+}
+
+- (void)testLoadFileFailsWithNilPath {
+  XCTestExpectation *resultExpectation =
+      [self expectationWithDescription:@"Should return failed result over the method channel."];
+  FLTWebViewController *controller =
+      [[FLTWebViewController alloc] initWithFrame:CGRectMake(0, 0, 300, 400)
+                                   viewIdentifier:1
+                                        arguments:nil
+                                  binaryMessenger:self.mockBinaryMessenger];
+  FLTWKWebView *mockWebView = OCMClassMock(FLTWKWebView.class);
+  controller.webView = mockWebView;
+  [controller onMethodCall:[FlutterMethodCall methodCallWithMethodName:@"loadFile" arguments:nil]
+                    result:^(id _Nullable result) {
+                      XCTAssertTrue([result class] == [FlutterError class]);
+                      FlutterError *errorResult = result;
+                      XCTAssertEqualObjects(errorResult.code, @"loadFile_failed");
+                      XCTAssertEqualObjects(errorResult.message, @"Failed parsing file path.");
+                      XCTAssertEqualObjects(errorResult.details, @"Argument is nil.");
+                      [resultExpectation fulfill];
+                    }];
+
+  [self waitForExpectations:@[ resultExpectation ] timeout:1.0];
+  OCMReject([mockWebView loadFileURL:[OCMArg any] allowingReadAccessToURL:[OCMArg any]]);
+}
+
+- (void)testLoadFileFailsWithNonStringPath {
+  XCTestExpectation *resultExpectation =
+      [self expectationWithDescription:@"Should return failed result over the method channel."];
+  FLTWebViewController *controller =
+      [[FLTWebViewController alloc] initWithFrame:CGRectMake(0, 0, 300, 400)
+                                   viewIdentifier:1
+                                        arguments:nil
+                                  binaryMessenger:self.mockBinaryMessenger];
+  FLTWKWebView *mockWebView = OCMClassMock(FLTWKWebView.class);
+  controller.webView = mockWebView;
+  [controller
+      onMethodCall:[FlutterMethodCall methodCallWithMethodName:@"loadFile" arguments:@(10)]
+            result:^(id _Nullable result) {
+              XCTAssertTrue([result class] == [FlutterError class]);
+              FlutterError *errorResult = result;
+              XCTAssertEqualObjects(errorResult.code, @"loadFile_failed");
+              XCTAssertEqualObjects(errorResult.message, @"Failed parsing file path.");
+              XCTAssertEqualObjects(errorResult.details, @"Argument is not of type NSString.");
+              [resultExpectation fulfill];
+            }];
+
+  [self waitForExpectations:@[ resultExpectation ] timeout:1.0];
+  OCMReject([mockWebView loadFileURL:[OCMArg any] allowingReadAccessToURL:[OCMArg any]]);
+}
+
+- (void)testLoadFileFailsWithEmptyPath {
+  XCTestExpectation *resultExpectation =
+      [self expectationWithDescription:@"Should return failed result over the method channel."];
+  FLTWebViewController *controller =
+      [[FLTWebViewController alloc] initWithFrame:CGRectMake(0, 0, 300, 400)
+                                   viewIdentifier:1
+                                        arguments:nil
+                                  binaryMessenger:self.mockBinaryMessenger];
+  FLTWKWebView *mockWebView = OCMClassMock(FLTWKWebView.class);
+  controller.webView = mockWebView;
+  [controller
+      onMethodCall:[FlutterMethodCall methodCallWithMethodName:@"loadFile" arguments:@""]
+            result:^(id _Nullable result) {
+              XCTAssertTrue([result class] == [FlutterError class]);
+              FlutterError *errorResult = result;
+              XCTAssertEqualObjects(errorResult.code, @"loadFile_failed");
+              XCTAssertEqualObjects(errorResult.message, @"Failed parsing file path.");
+              XCTAssertEqualObjects(errorResult.details, @"Argument contains an empty string.");
+              [resultExpectation fulfill];
+            }];
+
+  [self waitForExpectations:@[ resultExpectation ] timeout:1.0];
+  OCMReject([mockWebView loadFileURL:[OCMArg any] allowingReadAccessToURL:[OCMArg any]]);
+}
+
 - (void)testRunJavascriptFailsForNullString {
   // Setup
   FLTWebViewController *controller =

packages/webview_flutter/webview_flutter_wkwebview/example/lib/main.dart

@@ -6,8 +6,11 @@
 
 import 'dart:async';
 import 'dart:convert';
+import 'dart:io';
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:path_provider/path_provider.dart';
 import 'package:webview_flutter_platform_interface/webview_flutter_platform_interface.dart';
 
 import 'navigation_decision.dart';
@@ -33,6 +36,21 @@ The navigation delegate is set to block navigation to the youtube website.
 </html>
 ''';
 
+const String kLocalFileExamplePage = '''
+<!DOCTYPE html>
+<html lang="en">
+<head>
+<title>Local demo page</title>
+</head>
+<body>
+
+<h1>Local demo page</h1>
+<p>This is a local page used to demonstrate how to load a local file using the <a href="https://pub.dev/packages/webview_flutter">Flutter webview</a> plugin.</p>
+
+</body>
+</html>
+''';
+
 class _WebViewExample extends StatefulWidget {
   const _WebViewExample({Key? key}) : super(key: key);
 
@@ -120,6 +138,7 @@ enum _MenuOptions {
   listCache,
   clearCache,
   navigationDelegate,
+  loadLocalFile,
 }
 
 class _SampleMenu extends StatelessWidget {
@@ -157,6 +176,9 @@ class _SampleMenu extends StatelessWidget {
               case _MenuOptions.navigationDelegate:
                 _onNavigationDelegateExample(controller.data!, context);
                 break;
+              case _MenuOptions.loadLocalFile:
+                _onLoadLocalFileExample(controller.data!, context);
+                break;
             }
           },
           itemBuilder: (BuildContext context) => <PopupMenuItem<_MenuOptions>>[
@@ -189,6 +211,10 @@ class _SampleMenu extends StatelessWidget {
               value: _MenuOptions.navigationDelegate,
               child: Text('Navigation Delegate example'),
             ),
+            const PopupMenuItem<_MenuOptions>(
+              value: _MenuOptions.loadLocalFile,
+              child: Text('Load local file'),
+            ),
           ],
         );
       },
@@ -259,6 +285,13 @@ class _SampleMenu extends StatelessWidget {
     await controller.loadUrl('data:text/html;base64,$contentBase64');
   }
 
+  void _onLoadLocalFileExample(
+      WebViewController controller, BuildContext context) async {
+    String pathToIndex = await _prepareLocalFile();
+
+    await controller.loadFile(pathToIndex);
+  }
+
   Widget _getCookieList(String cookies) {
     if (cookies == null || cookies == '""') {
       return Container();
@@ -272,6 +305,20 @@ class _SampleMenu extends StatelessWidget {
       children: cookieWidgets.toList(),
     );
   }
+
+  static Future<String> _prepareLocalFile() async {
+    final String tmpDir = (await getTemporaryDirectory()).path;
+    File indexFile = File('$tmpDir/www/index.html');
+
+    if (await indexFile.exists()) {
+      return indexFile.path;
+    }
+
+    await Directory('$tmpDir/www').create(recursive: true);
+    await indexFile.writeAsString(kLocalFileExamplePage);
+
+    return indexFile.path;
+  }
 }
 
 class _NavigationControls extends StatelessWidget {

packages/webview_flutter/webview_flutter_wkwebview/example/lib/web_view.dart

@@ -305,6 +305,20 @@ class WebViewController {
 
   WebView _widget;
 
+  /// Loads the file located on the specified [absoluteFilePath].
+  ///
+  /// The [absoluteFilePath] parameter should contain the absolute path to the
+  /// file as it is stored on the device. For example:
+  /// `/Users/username/Documents/www/index.html`.
+  ///
+  /// Throws an ArgumentError if the [absoluteFilePath] does not exist.
+  Future<void> loadFile(
+    String absoluteFilePath,
+  ) {
+    assert(absoluteFilePath != null || absoluteFilePath.isNotEmpty);
+    return _webViewPlatformController.loadFile(absoluteFilePath);
+  }
+
   /// Loads the specified URL.
   ///
   /// If `headers` is not null and the URL is an HTTP URL, the key value paris in `headers` will

packages/webview_flutter/webview_flutter_wkwebview/example/pubspec.yaml

@@ -8,6 +8,9 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
+
+  path_provider: ^2.0.6
+
   webview_flutter_wkwebview:
     # When depending on this package from a real application you should use:
     #   webview_flutter: ^x.y.z
@@ -31,3 +34,4 @@ flutter:
   assets:
     - assets/sample_audio.ogg
     - assets/sample_video.mp4
+

packages/webview_flutter/webview_flutter_wkwebview/ios/Classes/FlutterWebView.m

@@ -135,6 +135,8 @@ - (UIView*)view {
 - (void)onMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
   if ([[call method] isEqualToString:@"updateSettings"]) {
     [self onUpdateSettings:call result:result];
+  } else if ([[call method] isEqualToString:@"loadFile"]) {
+    [self onLoadFile:call result:result];
   } else if ([[call method] isEqualToString:@"loadUrl"]) {
     [self onLoadUrl:call result:result];
   } else if ([[call method] isEqualToString:@"canGoBack"]) {
@@ -185,6 +187,22 @@ - (void)onUpdateSettings:(FlutterMethodCall*)call result:(FlutterResult)result {
   result([FlutterError errorWithCode:@"updateSettings_failed" message:error details:nil]);
 }
 
+- (void)onLoadFile:(FlutterMethodCall*)call result:(FlutterResult)result {
+  NSString* error = nil;
+  if (![FLTWebViewController isValidStringArgument:[call arguments] withErrorMessage:&error]) {
+    result([FlutterError errorWithCode:@"loadFile_failed"
+                               message:@"Failed parsing file path."
+                               details:error]);
+    return;
+  }
+
+  NSURL* url = [NSURL fileURLWithPath:[call arguments] isDirectory:NO];
+  NSURL* baseUrl = [url URLByDeletingLastPathComponent];
+
+  [_webView loadFileURL:url allowingReadAccessToURL:baseUrl];
+  result(nil);
+}
+
 - (void)onLoadUrl:(FlutterMethodCall*)call result:(FlutterResult)result {
   if (![self loadRequest:[call arguments]]) {
     result([FlutterError
@@ -517,6 +535,29 @@ - (void)updateUserAgent:(NSString*)userAgent {
   }
 }
 
++ (bool)isValidStringArgument:(id)argument withErrorMessage:(NSString**)errorDetails {
+  if (!argument) {
+    if (errorDetails) {
+      *errorDetails = @"Argument is nil.";
+    }
+    return NO;
+  }
+  if (![argument isKindOfClass:NSString.class]) {
+    if (errorDetails) {
+      *errorDetails = @"Argument is not of type NSString.";
+    }
+    return NO;
+  }
+  if (![argument length]) {
+    if (errorDetails) {
+      *errorDetails = @"Argument contains an empty string.";
+    }
+    return NO;
+  }
+
+  return YES;
+}
+
 #pragma mark WKUIDelegate
 
 - (WKWebView*)webView:(WKWebView*)webView