从iOS应用程序中的dropbox下载图像

Question

我正在尝试从iOS应用中的dropbox下载图片。我收到的错误如下：

  

[警告] DropboxSDK：向/1/files/dropboxeditimagemarvel.png发出错误请求 - （400）预期＆＃39; root＆＃39;要成为＆＃39; dropbox＆＃39;，＆＃39; sandbox＆＃39;或者＆＃39;自动＆＃39;，得到你的＆＃39; dropboxeditimagemarvel.png＆＃39;

在AppDelegate.m中：

DBSession* dbSession =
    [[DBSession alloc]
      initWithAppKey:@"23a9qum6roclx38" // add here app key
      appSecret:@"nh04ru3g53kgzat"  // add here app secret key
      root:kDBRootDropbox];// either kDBRootAppFolder or kDBRootDropbox
[DBSession setSharedSession:dbSession];

在UIViewController.m中

[restClient loadMetadata:@"/"];

- (void)restClient:(DBRestClient *)client loadedMetadata:(DBMetadata *)metadata
 {
    if (metadata.isDirectory)
    {
        NSArray *validExtensions = [NSArray arrayWithObjects:@"jpg", @"jpeg", @"png", nil];
        NSLog(@"Folder '%@' contains:", metadata.path);
        for (DBMetadata *file in metadata.contents) {
            NSLog(@"%@", file.filename);
            NSString* extension = [[file.path pathExtension] lowercaseString];
            if(![file isDirectory] && [validExtensions indexOfObject:extension]!=NSNotFound) {
                NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
                NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents directory
                NSString *filePath = [documentsDirectory stringByAppendingPathComponent:[@"/dropbox/" stringByAppendingString:@"example.png"]];
                NSError *error;
                 [restClient loadFile:file.filename intoPath:filePath];
                }
        }
    }
}

- (void)restClient:(DBRestClient *)client
loadMetadataFailedWithError:(NSError *)error {
    NSLog(@"Error loading metadata: %@", error);
}

- (void)restClient:(DBRestClient *)client loadedFile:(NSString *)localPath
       contentType:(NSString *)contentType metadata:(DBMetadata *)metadata {
    NSLog(@"File loaded into path: %@", localPath);
}

请帮助我......谢谢。