如何计算iOS中网络连接测试的负载大小和超时长度?

我的应用程序提供了从我们的服务器下载3430个高分辨率图像的选项,每个图像大小为50k-600k字节。

最初的方法是下载所有这些文件,但我们意识到这会导致很多nsurlertimedout错误并使我们的程序崩溃。我们现在已经实现了它,这样我们就可以下载所有的图像,但一次只能下载100个图像。

- (void)batchDownloadImagesFromServer:(BOOL)downloadHiResImages
{

    [UIApplication sharedApplication].idleTimerDisabled = YES;
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];

    [self generateImageURLList:YES];

    [leafletImageLoaderQueue removeAllObjects];
    numberOfThumbnailLeft = [uncachedThumbnailArray count];
    numberOfHiResImageLeft = [uncachedHiResImageArray count];

    NSLog(@"DEBUG: In batchDownloadImagesFromServer numberOfThumbnailLeft %ul , numberOfHiResImageLeft %ul ", numberOfThumbnailLeft, numberOfHiResImageLeft);

    numberOfImagesToDownload = numberOfThumbnailLeft;
    if (downloadHiResImages)
    {
        numberOfImagesToDownload += numberOfHiResImageLeft;
    }

    if (numberTotalToDownload < 0) {
        numberTotalToDownload = numberOfHiResImageLeft;
    }

    int midBatchCt = 0;
    // start where we stopped
    NSArray *subArray;
    NSRange batchRange;
    batchRange.location = 0;//uncachedHiResIndex;
    NSInteger uncachedNumber = [uncachedHiResImageArray count];
    NSLog(@"uncachedHiResIndex and numberTotalToDownload: %d %d", uncachedHiResIndex, numberTotalToDownload);
    if (uncachedHiResIndex >= numberTotalToDownload || batchRange.location >= uncachedNumber) {
        // we have reached the end of the uncached hires images

        NSLog(@" END of download total to download=%ld , uncachedNumber=%ld, # not downloaded is %ld", (long)numberTotalToDownload, uncachedNumber, (long)numberFailedToDownload);
        return;
    }
    if (batchRange.location+100 > uncachedNumber) {
        NSInteger imagesUntilEnd = uncachedNumber -1;
        batchRange.length = imagesUntilEnd;
        NSLog(@"this is uncached number: %d this is uncachedhiresindex:%d and this images until end:%d ", uncachedNumber, uncachedHiResIndex, imagesUntilEnd);

    } else {
        batchRange.length = 100;
    }
    NSLog(@" NEW RANGE is from %lul to %lul ", (unsigned long)batchRange.location, batchRange.length);
    subArray = [uncachedHiResImageArray subarrayWithRange:batchRange];
    if (downloadHiResImages)
    {
        for ( LeafletURL* aLeafletURL in subArray )
        {
            LeafletImageLoader* hiResImageLoader = [[LeafletImageLoader alloc] initWithDelegate:self];
            [leafletImageLoaderQueue addObject:hiResImageLoader]; // do this before making connection!! //

            [hiResImageLoader loadImage:aLeafletURL isThumbnail:NO   isBatchDownload:YES];

            //// Adding object to array already retains it, so it's safe to release it here. ////
            [hiResImageLoader release];

            midBatchCt++;
            uncachedHiResIndex++;
            if (midBatchCt == 10) {
                NSLog(@" Waiting for queued images to download...");
                NSLog(@" REMOVED from QUEUE %lul , UncachedIndex %lul", numberRemovedFromQueue, uncachedHiResIndex);
                break;
            }
        }
    }



    if ( [leafletImageLoaderQueue count] == 0 && numberRemovedFromQueue == numberTotalToDownload) {
        if([delegate respondsToSelector:@selector(requestDidBatchDownloadImages:)])
        {
            [delegate requestDidBatchDownloadImages:self];
        }
    }


}

这解决了我们的大部分问题。但是,我们希望在开始批量下载之前测试网络连接。我找到一个 low level ping library 这样可以得到准确的往返计时结果。使用GBPing的演示代码作为参考,我在调用之前编写了自己的代码来ping服务器 batchDownloadImagesFromServer .

- (IBAction)preloadAll:(id)sender
{
self.ping = [GBPing new];
    self.ping.host = kDefaultDataServer;
    self.ping.delegate = self;
    self.ping.timeout = 1;
    self.ping.pingPeriod = 0.9;

    // setup the ping object (this resolves addresses etc)
    [self.ping setupWithBlock:^(BOOL success, NSError *error) {
        if (success) {
            // start pinging
            [self.ping startPinging];

            // stop it after 5 seconds
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                NSLog(@"stop it");
                [self.ping stop];
                self.ping = nil;
            });
        } else {
            UIAlertController * alert = [UIAlertController alertControllerWithTitle:@"Internet Connection"
                                                                            message:@"Not strong enough internet connection"
                                                                     preferredStyle:UIAlertControllerStyleAlert];

            UIAlertAction* OKButton = [UIAlertAction
                                        actionWithTitle:@"Ok"
                                        style:UIAlertActionStyleCancel
                                        handler:^(UIAlertAction * action) {
                                            [downloadManager batchDownloadImagesFromServer:YES];
                                        }];

            [alert addAction:OKButton];
            [self presentViewController:alert animated:NO completion:nil];
        }

    }];
}

我完全不熟悉网络 . 考虑到批处理大小和图像大小,如何确定测试的有效负载大小和超时长度?