NSURLConnection類實現下載網路圖片

這是蘋果SDK自帶的一個下載類，使用簡單；

首先要接受<NSURLConnectionDataDelegate>協議

- (void)viewDidLoad
{
    [super viewDidLoad];
    _data = [[NSMutableData alloc]init];
    _imageView = [[UIImageView alloc]initWithFrame:self.view.frame];
    [[self view]addSubview:_imageView];
        NSString * path = @"http://d.hiphotos.baidu.com/image/w%3D2048/sign=17bd9a6396eef01f4d141fc5d4c69825/94cad1c8a786c917dc0c713ecb3d70cf3bc757ad.jpg";
    [self startDownloadWithPath:path];
    
   
}
//實現現在的協議方法
-(void)startDownloadWithPath:(NSString*)path{
    NSURL * url = [[NSURL alloc]initWithString:path];
    NSURLRequest * request = [[NSURLRequest alloc]initWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:30];
    _connection = [[NSURLConnection alloc]initWithRequest:request delegate:self startImmediately:YES];
   
}

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
    [_data setLength:0];
     [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
}


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

-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
    _imageView.image = [UIImage imageWithData:_data];
    [[UIApplication sharedApplication]setNetworkActivityIndicatorVisible:NO];
}

執行程式後模擬器顯示如下：