ios - 异步下载 - 右模式

Question

我需要从我的网站下载一些图片。我使用来自应用程序的图像的 url 创建了一个 XML 文件，我读取了这个文件并将所有 url 存储在一个数组中。

现在，我需要下载所有图像，我想异步地下载它，我想知道最好的方法，现在我的代码是:

    for (int i=0; i<self.arrayAggiornamenti.count; i++) {

        Aggiornamento *aggiornamento = [self.arrayAggiornamenti objectAtIndex:i];
        NSMutableArray *arrayPath = aggiornamento.arrayPaths;

        for (int j=0; j<arrayPath.count; j++) {

            NSString *urlString = [NSString stringWithFormat:@"http://www.xxx.com/%@",[arrayPath objectAtIndex:j]];

            NSString *urlStringEncoded = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

            NSURL *urlImage = [NSURL URLWithString:urlStringEncoded];

            NSURLRequest *requestImgage = [NSURLRequest requestWithURL:urlImage
                                                        cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
                                                    timeoutInterval:60];

            self.imgData = [[NSMutableData alloc] init];

            self.imgConnection = [[NSURLConnection alloc] initWithRequest:requestImgage delegate:self startImmediately:YES];
        }
}

- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{

    // Start parsing XML
    if (connection == self.xmlConnection) {
    }
    // Start download Totale
    else if (connection == self.toatalConnection) {
    }
    // Start connessione immagini
    else {        
        [self.imgData writeToFile:pathFile atomically:YES];
    }
}

- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

    if (connection == self.xmlConnection) {
    }
    else if (connection == self.toatalConnection) {
    }
    else {
        [self.imgData appendData:data];
    }

}
- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {}

- (void) connectionDidFinishLoading:(NSURLConnection *)connection {

    if (connection == self.xmlConnection) {
    }
    else if (connection == self.toatalConnection) {
    }
    else if (connection == self.imgConnection){
    }
}

使用此代码可以下载图像，但问题是如果我在 didReciveResponse 上添加 if else (connection==self.imgConnection)，应用程序只下载第一张图像，为什么？这样下载多张图片正确吗？

Answer 1

可能是因为您正在循环内分配 self.imgData。请引用此链接以下载数组内的图像:What is asynchronous image downloading and how can I download too many images?