Question

我有一个包含json格式的网址。

{
      "name":"RAI Radiodue",
      "cat":"Adult Contemporary",
      "img":"http://www.rai.it/dl/portaleRadio/images/ico_radio2.jpg",
      "url":"http://www.listenlive.eu/rai2.m3u"
   },
   {
      "name":"RAI Radiotre",
      "cat":"Classical/Culture",
      "img":"http://www.rai.it/dl/portaleRadio/images/ico_radio3.jpg",
      "url":"http://www.listenlive.eu/rai3.m3u"
   }........etc

我正在尝试使用以下代码显示许多单选按钮：

    for (int i = 0;  i<[namesArray count]; i++) {

        NSURL *url = [NSURL URLWithString: [pictureUrl objectAtIndex:i]];

        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImageView *subview = [[UIImageView alloc] init];
        [subview setImage:[UIImage imageWithData:data]];



        UIButton *bt = [UIButton buttonWithType:UIButtonTypeCustom];

        int xxx = i%3;
        int yyy = i/3.0f;
        [bt setFrame:CGRectMake(35+95*xxx, 15+100*yyy, 60, 60)];
        [bt setBackgroundImage:subview forState:UIControlStateNormal];

        bt.tag = 200+i;
        bt.selected = NO;
        [bt.layer setMasksToBounds:NO];
        [bt.layer setShadowColor:[UIColor blackColor].CGColor];
        [bt.layer setShadowOpacity:0.8f];
        [bt.layer setShadowOffset:CGSizeMake(1.0f, 1.0f)];
        [bt addTarget:self action:@selector(Play:) forControlEvents:UIControlEventTouchUpInside];
        [mainscroll addSubview:bt];
}

并为每个按钮添加一个已填充的pictureUrl中的图像，但是当我想要转到此视图控制器时，我在控制台中获得此输出：

2014-12-18 17:32:40.763 TV[3128:935103] NSURLConnection/CFURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9813)
2014-12-18 17:32:46.041 TV[3128:935134] void SendDelegateMessage(NSInvocation *): delegate (webView:decidePolicyForNavigationAction:request:frame:decisionListener:) failed to return after waiting 10 seconds. main run loop mode: kCFRunLoopDefaultMode.

我该怎么办？

Answer 1

NSData *data = [NSData dataWithContentsOfURL:url];

此行阻塞主线程，主线程在运行此行之前等待数据下载：

UIImageView *subview = [[UIImageView alloc] init];
[subview setImage:[UIImage imageWithData:data]];

您必须在其他线程中运行下载数据，并在下载数据时设置图像。

Answer 2

必须有pictureUrl数组出错，或者在运行代码时没有互联网连接。当我运行你的代码，传入你在帖子中显示的2个字符串时，代码工作正常，

- (void)viewDidLoad {
    [super viewDidLoad];
    NSArray *stringsArray = @[@"http://www.rai.it/dl/portaleRadio/images/ico_radio2.jpg", @"http://www.rai.it/dl/portaleRadio/images/ico_radio3.jpg"];
    [self downloadImagesFromNamesArray:stringsArray];

}

-(void)downloadImagesFromNamesArray:(NSArray *) namesArray {
    for (int i = 0;  i<[namesArray count]; i++) {

        NSURL *url = [NSURL URLWithString: [namesArray objectAtIndex:i]];

        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImage *img = [UIImage imageWithData:data];

        UIButton *bt = [UIButton buttonWithType:UIButtonTypeCustom];

        int xxx = i%3;
        int yyy = i/3.0f;
        [bt setFrame:CGRectMake(35+95*xxx, 15+100*yyy, 60, 60)];
        [bt setBackgroundImage:img forState:UIControlStateNormal];

        bt.tag = 200+i;
        bt.selected = NO;
        [bt.layer setMasksToBounds:NO];
        [bt.layer setShadowColor:[UIColor blackColor].CGColor];
        [bt.layer setShadowOpacity:0.8f];
        [bt.layer setShadowOffset:CGSizeMake(1.0f, 1.0f)];
        [bt addTarget:self action:@selector(Play:) forControlEvents:UIControlEventTouchUpInside];
        [self.mainscroll addSubview:bt];
    }
}

另请注意，我修复了您尝试使用图像视图而不是图像设置按钮背景图像的问题。

更好的下载方法是使用异步下载方法，如sendAsynchronousRequest：queue：completionHandler :(或NSURLSession方法）。如果您这样做，您将得到一些错误处理，并且在下载发生时不会阻止该应用程序。这样做时，你不能使用循环，而是应该从异步方法的完成块下载下一个图像。

-(void) downloadImagesFromNamesArray:(NSArray *) imageURLStrings {
    static int count = 0;
    NSString *urlString = imageURLStrings[count];
    NSURL *url = [NSURL URLWithString:urlString];
    NSURLRequest *req = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:10];
    [NSURLConnection sendAsynchronousRequest:req queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        if (connectionError) {
            NSLog(@"%@", connectionError);
            count ++;
            if (count < imageURLStrings.count) {
                [self downloadImagesFromNamesArray:imageURLStrings];
            }
        }else{
            UIImage *img = [UIImage imageWithData:data];
            if (img) {
                UIButton *bt = [UIButton buttonWithType:UIButtonTypeCustom];

                int xxx = count%3;
                int yyy = count/3.0f;
                [bt setFrame:CGRectMake(35+95*xxx, 15+100*yyy, 60, 60)];
                [bt setBackgroundImage:img forState:UIControlStateNormal];

                bt.tag = 200+ count;
                bt.selected = NO;
                [bt.layer setMasksToBounds:NO];
                [bt.layer setShadowColor:[UIColor blackColor].CGColor];
                [bt.layer setShadowOpacity:0.8f];
                [bt.layer setShadowOffset:CGSizeMake(1.0f, 1.0f)];
                [bt addTarget:self action:@selector(Play:) forControlEvents:UIControlEventTouchUpInside];
                [self.mainscroll addSubview:bt];
            }else{
                NSLog(@"Data was received but no image was created from the data");
            }

            count ++;
            if (count < imageURLStrings.count) {
                [self downloadImagesFromNamesArray:imageURLStrings];
            }
        }
    }];
}

来自url的按钮图像 - 等待10秒后仍无法返回。主运行循环模式：kCFRunLoopDefaultMode

2 个答案: