【发布时间】：2012-04-03 08:26:51
【问题描述】：
我的应用程序中有基本的 iCloud 支持（同步更改、无处不在等），但到目前为止，一个关键的遗漏是缺乏对云中存在（或有更改）文件的“下载”支持，但与当前磁盘上的内容不同步。
我在我的应用程序中添加了以下方法，基于一些 Apple 提供的代码，并进行了一些调整：
下载方式：
- (BOOL)downloadFileIfNotAvailable:(NSURL*)file {
NSNumber* isIniCloud = nil;
if ([file getResourceValue:&isIniCloud forKey:NSURLIsUbiquitousItemKey error:nil]) {
// If the item is in iCloud, see if it is downloaded.
if ([isIniCloud boolValue]) {
NSNumber* isDownloaded = nil;
if ([file getResourceValue:&isDownloaded forKey:NSURLUbiquitousItemIsDownloadedKey error:nil]) {
if ([isDownloaded boolValue])
return YES;
// Download the file.
NSFileManager* fm = [NSFileManager defaultManager];
NSError *downloadError = nil;
[fm startDownloadingUbiquitousItemAtURL:file error:&downloadError];
if (downloadError) {
NSLog(@"Error occurred starting download: %@", downloadError);
}
return NO;
}
}
}
// Return YES as long as an explicit download was not started.
return YES;
}
- (void)waitForDownloadThenLoad:(NSURL *)file {
NSLog(@"Waiting for file to download...");
id<ApplicationDelegate> appDelegate = [DataLoader applicationDelegate];
while (true) {
NSDictionary *fileAttribs = [[NSFileManager defaultManager] attributesOfItemAtPath:[file path] error:nil];
NSNumber *size = [fileAttribs objectForKey:NSFileSize];
[NSThread sleepForTimeInterval:0.1];
NSNumber* isDownloading = nil;
if ([file getResourceValue:&isDownloading forKey:NSURLUbiquitousItemIsDownloadingKey error:nil]) {
NSLog(@"iCloud download is moving: %d, size is %@", [isDownloading boolValue], size);
}
NSNumber* isDownloaded = nil;
if ([file getResourceValue:&isDownloaded forKey:NSURLUbiquitousItemIsDownloadedKey error:nil]) {
NSLog(@"iCloud download has finished: %d", [isDownloaded boolValue]);
if ([isDownloaded boolValue]) {
[self dispatchLoadToAppDelegate:file];
return;
}
}
NSNumber *downloadPercentage = nil;
if ([file getResourceValue:&downloadPercentage forKey:NSURLUbiquitousItemPercentDownloadedKey error:nil]) {
double percentage = [downloadPercentage doubleValue];
NSLog(@"Download percentage is %f", percentage);
[appDelegate updateLoadingStatusString:[NSString stringWithFormat:@"Downloading from iCloud (%2.2f%%)", percentage]];
}
}
}
以及启动/检查下载的代码：
if ([self downloadFileIfNotAvailable:urlToUse]) {
// The file is already available. Load.
[self dispatchLoadToAppDelegate:[urlToUse autorelease]];
} else {
// The file is downloading. Wait for it.
[self performSelector:@selector(waitForDownloadThenLoad:) withObject:[urlToUse autorelease] afterDelay:0];
}
据我所知上面的代码看起来不错，但是当我在设备 A 上进行大量更改时，保存这些更改，然后打开设备 B（提示在设备上下载B）这是我在控制台中看到的：
2012-03-18 12:45:55.858 MyApp[12363:707] Waiting for file to download...
2012-03-18 12:45:58.041 MyApp[12363:707] iCloud download is moving: 0, size is 101575
2012-03-18 12:45:58.041 MyApp[12363:707] iCloud download has finished: 0
2012-03-18 12:45:58.041 MyApp[12363:707] Download percentage is 0.000000
2012-03-18 12:45:58.143 MyApp[12363:707] iCloud download is moving: 0, size is 101575
2012-03-18 12:45:58.143 MyApp[12363:707] iCloud download has finished: 0
2012-03-18 12:45:58.144 MyApp[12363:707] Download percentage is 0.000000
2012-03-18 12:45:58.246 MyApp[12363:707] iCloud download is moving: 0, size is 101575
2012-03-18 12:45:58.246 MyApp[12363:707] iCloud download has finished: 0
2012-03-18 12:45:58.246 MyApp[12363:707] Download percentage is 0.000000
2012-03-18 12:45:58.347 MyApp[12363:707] iCloud download is moving: 0, size is 177127
2012-03-18 12:45:58.347 MyApp[12363:707] iCloud download has finished: 0
2012-03-18 12:45:58.347 MyApp[12363:707] Download percentage is 0.000000
2012-03-18 12:45:58.449 MyApp[12363:707] iCloud download is moving: 0, size is 177127
2012-03-18 12:45:58.449 MyApp[12363:707] iCloud download has finished: 0
2012-03-18 12:45:58.450 MyApp[12363:707] Download percentage is 0.000000
所以无论出于何种原因：
- 文件下载开始时没有错误
- 文件下载状态的文件属性始终返回未下载、未下载完成、进度为0%。
- 即使在两次检查之间文件大小发生变化，我也会永远陷入循环中。
我做错了什么？
【问题讨论】：
标签： objective-c ios macos icloud