Question

我有一个应用需要下载声音文件才能正常工作。

我正在异步使用NSURLConnection来下载超过20Mb的文件。我放置了一个progressBarView来跟踪下载的百分比，我正在使用Apple建议的NSUrlConnection委托方法。

NSURLRequest *theRequest=[NSURLRequest requestWithURL:soundFileURL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:20.0];
// create the connection with the request
// and start loading the data
NSURLConnection *theConnection;

theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

//[theConnection cancel];
//[theConnection start];
if (theConnection) {
    // Create the NSMutableData that will hold
    // the received data
    // receivedData is declared as a method instance elsewhere
    receivedData=[[NSMutableData data] retain];
} else {
    // inform the user that the download could not be made
}

和委托方法

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    [receivedData appendData:data];
}

所以......

当我开始下载时，界面会不时挂起，progressView也会挂起。

一个值得注意的事情，也许是另一个问题：我禁用了用户界面，因此用户必须等到下载完成，当然，我给他一个消息告诉他。 Apple会拒绝我的应用吗？我非常担心

感谢您阅读我的问题：）

Answer 1

NSUrlConnection默认情况下将NSURLConnectionDelegate的事件发送到主线程。您应该为此连接创建新池和runloop，并确保在后台处理它。以下是在后台下载图像的示例。它使用修改后的NSOperationQueue和NSOperation，但您可以轻松修改它以下载文件。 LinkedImageFetcher on developer.apple.com

Answer 2

 //1 First allocate NSOperationQueue object and set number of concurrent operations to execute at a time 

 NSOperationQueue *thumbnailQueue = [[NSOperationQueue alloc] init];
    thumbnailQueue.maxConcurrentOperationCount = 3;
// load photo images in the background
    __weak BHCollectionViewController *weakSelf = self;
    NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
        UIImage *image = [photo image];

        dispatch_async(dispatch_get_main_queue(), ^{
            // then set them via the main queue if the cell is still visible.

                cell.imageView.image = image;
            }
        });
    }];

    operation.queuePriority = (indexPath.item == 0) ?
        NSOperationQueuePriorityHigh : NSOperationQueuePriorityNormal;

    [thumbnailQueue addOperation:operation];

创建NSObject的Photo类并添加以下方法

- (UIImage *)image
{
    if (!_image && self.imageURL) {
        NSData *imageData = [NSData dataWithContentsOfURL:self.imageURL];
        UIImage *image = [UIImage imageWithData:imageData scale:[UIScreen mainScreen].scale];

        _image = image;
    }

    return _image;
}

当我开始使用NsurlConnection下载时，我的应用程序挂起

2 个答案: