iphone - NSURLConnection 数据请求结束时没有数据

Question

我正在使用 NSURLConnection 下载位图。我将委托(delegate)设置为 self，并实现方法 connection:didReceiveData 和 connectionDidFinishLoading。收到数据后，我将其存储在 NSMutableData 对象(称为 input)中，然后在连接结束时，我使用它来创建位图。问题是我在 connection:didReceiveData 中收到数据，但在 connection:DidFinishLoading 中为空。我该如何解决这个问题？

- (void)start
{
    NSURL *url = [NSURL URLWithString:src];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

    connection = [[NSURLConnection alloc] initWithRequest:request
                                                 delegate:self
                                         startImmediately:YES];
}

- (void)connection:(NSURLConnection *)conn
    didReceiveData:(NSData *)d
{
    NSLog(@"Data Received: %@", d);//This prints the correct data
    //Add data chunk to input
    [input appendData:d];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)conn
{
    CPLog(@"Finished Receiving bitmap from server. Data received with length %d: %@", [input length], input);//this prints length 0 and a value of (null)
    CFDataRef imgData = (__bridge CFDataRef) input;
    CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData (imgData);
    CGImageRef image;
    if (!imgDataProvider)
    {
        NSLog(@"Request Failed!");//happens every time
        [callback handleBitmap:nil];
        return;
    }

    image = CGImageCreateWithJPEGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault);


    [callback handleBitmap:image];
    return;

}

Answer 1

您应该为input 属性分配内存。通常在开始新的 url 连接之前完成:

- (void)start
{
    self.input = [NSMutableData data];
    // .... init and start url connection
}