javascript - 不允许加载本地资源 : file:///var/mobile/Containers/Data/Application/03F63826-7849-47C3-A6DF-E1EB1113FF0A/Documents/xxx. png

Question

XCode 10.1
iOS 12.0.1

我使用wkwebview的函数“evaluateJavaScript”来回调图片url，让wkwebview可以显示这张图片。
它在模拟器中成功运行。
但它在设备上失败了。
这有什么问题吗？

模拟器 url 很不错:

file:///Users/xxxxxx/Library/Developer/CoreSimulator/Devices/8FB6E110-F30F-425D-9011-A196E78BE7CB/data/Containers/Data/Application/E122A32D-7E21-4EBA-A9E7-BC15E8468A11/Documents/20190409150915.png

设备 url 失败:

Not allowed to load local resource: file:///var/mobile/Containers/Data/Application/03F63826-7849-47C3-A6DF-E1EB1113FF0A/Documents/20190408203417.png

NSArray *imagesArray = [[NSArray alloc] initWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:@"pickerImages"]];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];    
NSString *filePath = [NSString stringWithFormat:@"file://%@/",documentsDirectory];
NSString *imagesString = pickerImagesArray.firstObject;
NSString *jscript = @"";

if ([imagesString isEqualToString:@""])
    {
        jscript = [NSString stringWithFormat:@"getimage_cb('%@')" ,  @""];
    } else {
        NSString  *output = [NSString stringWithFormat:@"%@%@",filePath,imagesString];
        jscript = [NSString stringWithFormat:@"%@", [NSString stringWithFormat:@"getimage_cb('%@')" ,  output]];
    }

    [self.myWkwebView evaluateJavaScript:jscript completionHandler:^(id object, NSError * _Nullable error) {
    }];

Answer 1

关于这个特定主题，SO 上有相互矛盾的答案。

我读到的是，您可以直接从应用程序的包中加载图像，但不能从其文档目录中加载图像。

一种可能的解决方法是将图像加载到 UIImage 实例中，将其转换为 base64 并将其传递给 evaluateJavascript 方法:

    NSArray *imagesArray = [[NSArray alloc] initWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:@"pickerImages"]];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];    
    NSString *imagesString = [pickerImagesArray firstObject];
    NSString *filePath = [NSString stringWithFormat:@"%@/%@", documentsDirectory, imagesString];

    //Init UIImage Instance
    UIImage *uiImageInstance = [[UIImage alloc] initWithContentsOfFile:filePath];

    //Get PNG Representation as NSData
    NSData *data = UIImagePNGRepresentation(uiImageInstance);

    //Convert to Base64
    NSString *base64Str = [data base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];

    //Construct the attribute value we'll pass in the javascript
    NSString *attribute = [NSString stringWithFormat: @"data:image/png;base64,%@", base64Str];

    //Set the image within the webview
    [self.myWkwebView evaluateJavascript: [NSString stringWithFormat: @"document.getElementById('img').setAttribute( 'src', %@);", attribute] completionHandler:^(id object, NSError * _Nullable error) {}];