暂停和恢复 ASINetworkQueue

Question

我正在使用 ASINetworkQueue 在 iPad 应用程序中下载大约 50 个文件。我正在寻找一种允许用户暂停和恢复队列的方法。

ASIHTTP 文档提到，

[request setAllowResumeForFileDownloads:YES];

但这在单个请求级别运行，而不是在队列级别运行。由于 ASINetworkQueue 是 NSOperationQueue 的子类，我也尝试过

[queue setSuspended:YES];

，虽然这会暂停队列，但它不会影响正在进行的下载，它只是等待下载完成，然后暂停队列，在我的情况下这意味着很多秒在用户按下按钮和队列实际暂停之间，这不是我想要的 UI 体验。

谁能建议另一种方法来解决这个问题？

Answer 1

我的解决方案..

- (void) pause
{
    if(self.queue && self.queue.requestsCount>0)
    {
        NSLog(@"%@", self.queue.operations);

        for (ASIHTTPRequest * req in self.queue.operations) {
            req.userInfo = [NSDictionary dictionaryWithObject:@"1" forKey:@"ignore"];
        }

        [self.queue.operations makeObjectsPerformSelector:@selector(cancel)];

        [self.queue setSuspended:YES];

        for (ASIHTTPRequest * req in self.queue.operations) {
            ASIHTTPRequest * newReq = [[ASIHTTPRequest alloc] initWithURL:req.url];
            [newReq setDownloadDestinationPath:req.downloadDestinationPath];
            [newReq setTemporaryFileDownloadPath:req.temporaryFileDownloadPath];
//            [newReq setAllowResumeForFileDownloads:YES];
            [newReq setUserInfo:req.userInfo];
            [self.queue addOperation:newReq];

        }

    }
}

- (void) resume
{
    if(self.queue && self.queue.requestsCount>0)
    {
        [self _setupQueue];
        [self.queue go];
    }
}

- (void) _setupQueue
{
    [self.queue setShouldCancelAllRequestsOnFailure:NO];
    [self.queue setRequestDidStartSelector:@selector(downloadDidStart:)];
    [self.queue setRequestDidFinishSelector:@selector(downloadDidComplete:)];
    [self.queue setRequestDidFailSelector:@selector(downloadDidFailed:)];
    [self.queue setQueueDidFinishSelector:@selector(queueDidFinished:)];
    [self.queue setDownloadProgressDelegate:self.downloadProgress];
    [self.queue setDelegate:self];
    self.queue.maxConcurrentOperationCount = 3;
//    self.queue.showAccurateProgress = YES;
}

首先，暂停函数取消所有正在运行的操作，并重新创建新请求将它们推入队列。
然后恢复函数取消暂停队列。
注意，请求不要设置setAllowResumeForFileDownloads:YES，否则totalBytesToDownload会计算错误。如果allowResumeForFileDownloads=NO，其值将与队列中的请求数相同。

这是我的请求失败处理程序，我在文件下载失败时添加重试。但我不希望取消请求时会调用重试机制，因此我将 userInfo(ignore:true) 设置为 request 对象以防止发生这种情况。

- (void) downloadDidFailed:(ASIHTTPRequest *)req
{
    NSLog(@"request failed");
    NSLog(@"%d", self.queue.requestsCount);

    if(![self.queue showAccurateProgress])
    {
        [self.queue setTotalBytesToDownload:[self.queue totalBytesToDownload]-1];
        NSLog(@"totalBytesToDownload=%lld", self.queue.totalBytesToDownload);
    }

    NSDictionary * userInfo = req.userInfo;
    if([[userInfo valueForKey:@"ignore"] boolValue]) return; // ignore retry

    int retryTimes = [[req.userInfo objectForKey:@"retryTimes"] intValue];
    if(retryTimes<kMU_MaxRetry)
    {
        ++ retryTimes;
        NSLog(@"retry %d", retryTimes);
        ASIHTTPRequest * newReq = [ASIHTTPRequest requestWithURL:req.url];
        [newReq setDownloadDestinationPath:req.downloadDestinationPath];
        [newReq setTemporaryFileDownloadPath:req.temporaryFileDownloadPath];
        newReq.userInfo = [NSDictionary dictionaryWithObject:[NSString stringWithFormat:@"%d", retryTimes] forKey:@"retryTimes"];
        [self.queue addOperation:newReq];

        NSLog(@"%d", self.queue.requestsCount);
    }else{  // reach max retry, fail it
        [self.failures addObject:req];
    }
}

不知道有没有更好的解决办法，希望可以帮到你。