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 文档参考

[request setAllowResumeForFileDownloads:YES];

但这在单个请求级别而不是队列级别上运行。由于 ASINetworkQueue 是 NSOperationQueue 的子类，我也尝试过

[queue setSuspended:YES];

虽然这会暂停一个队列，但它不会影响正在进行的下载，它只是等到它们完成然后暂停队列，这在我的情况下意味着用户按下按钮和队列之间的许多秒实际上是暂停，这不是我想要的 UI 体验。

谁能提出另一种解决这个问题的方法？

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，暂停功能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 resume 函数取消挂起队列。 注意，request不应该设置setAllowResumeForFileDownloads:YES，否则totalBytesToDownload会计算错误。如果allowResumeForFileDownloads=NO，它的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。但是我不希望当我取消请求时，会调用重试机制，所以我将 userInfo(ignore:true) 设置为请求对象以防止它发生。

- (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，希望能帮到你。