如何从 UIWebView 下载文件并再次打开

Question

我如何创建一个“下载管理器”，它可以检测您点击的链接（在 UIWebView 中）何时具有以 ".pdf"、".png"、".jpeg"、".tiff 结尾的文件"、".gif"、".doc"、".docx"、".ppt"、".pptx"、".xls" 和 ".xlsx" 然后会打开一个 UIActionSheet 询问您是否想下载或打开。如果您选择下载，它将将该文件下载到设备。

应用程序的另一部分将在 UITableView 中显示已下载文件的列表，当您点击它们时，它们将显示在 UIWebView 中，但当然是离线的，因为它们会像下载时一样在本地加载。

请参阅http://itunes.apple.com/gb/app/downloads-lite-downloader/id349275540?mt=8 以更好地了解我想要做什么。

最好的方法是什么？

Answer 1

在你的 UiWebView 的委托中使用方法- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType 来确定它何时想要加载资源。

当方法 get 被调用时，您只需要从参数(NSURLRequest *)request 解析 URL，如果它是您想要的类型之一，则返回 NO 并继续您的逻辑 (UIActionSheet)，如果用户只是单击了一个，则返回 YES指向 HTML 文件的简单链接。

有道理吗？

Edit_：为了更好地理解快速代码示例

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
     if(navigationType == UIWebViewNavigationTypeLinkClicked) {
          NSURL *requestedURL = [request URL];
          // ...Check if the URL points to a file you're looking for...
          // Then load the file
          NSData *fileData = [[NSData alloc] initWithContentsOfURL:requestedURL;
          // Get the path to the App's Documents directory
          NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
          NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
          [fileData writeToFile:[NSString stringWithFormat:@"%@/%@", documentsDirectory, [requestedURL lastPathComponent]] atomically:YES];
     } 
}

Edit2_：我们在聊天中讨论了您的问题后，我更新了代码示例：

- (IBAction)saveFile:(id)sender {
    // Get the URL of the loaded ressource
    NSURL *theRessourcesURL = [[webView request] URL];
    NSString *fileExtension = [theRessourcesURL pathExtension];

    if ([fileExtension isEqualToString:@"png"] || [fileExtension isEqualToString:@"jpg"]) {
        // Get the filename of the loaded ressource form the UIWebView's request URL
        NSString *filename = [theRessourcesURL lastPathComponent];
        NSLog(@"Filename: %@", filename);
        // Get the path to the App's Documents directory
        NSString *docPath = [self documentsDirectoryPath];
        // Combine the filename and the path to the documents dir into the full path
        NSString *pathToDownloadTo = [NSString stringWithFormat:@"%@/%@", docPath, filename];


        // Load the file from the remote server
        NSData *tmp = [NSData dataWithContentsOfURL:theRessourcesURL];
        // Save the loaded data if loaded successfully
        if (tmp != nil) {
            NSError *error = nil;
            // Write the contents of our tmp object into a file
            [tmp writeToFile:pathToDownloadTo options:NSDataWritingAtomic error:&error];
            if (error != nil) {
                NSLog(@"Failed to save the file: %@", [error description]);
            } else {
                // Display an UIAlertView that shows the users we saved the file :)
                UIAlertView *filenameAlert = [[UIAlertView alloc] initWithTitle:@"File saved" message:[NSString stringWithFormat:@"The file %@ has been saved.", filename] delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
                [filenameAlert show];
                [filenameAlert release];
            }
        } else {
            // File could notbe loaded -> handle errors
        }
    } else {
        // File type not supported
    }
}

/**
    Just a small helper function
    that returns the path to our 
    Documents directory
**/
- (NSString *)documentsDirectoryPath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectoryPath = [paths objectAtIndex:0];
    return documentsDirectoryPath;
}