使用GCD在后台创建UIKit对象是一种不好的做法吗？ [英] Is the creation of an UIKit object in background using GCD a bad practice?

问题描述

bbum 指出的 此处，文档中
表示： 在大多数情况下，UIKit类只能在应用程序的主线程中使用。对于派生类UIResponder或涉及操纵，尤其如此 。

我以为我知道不能在后台线程中调用绘图方法，所以可以在后台完成创建，因为只有在添加视图时才调用drawRect方法。但是也许我错了。

I thought I understood that the methods of drawings could not be called in a background thread, so that the creation could be done in the background, as the drawRect method is only called when the view is added. But maybe i am wrong.

总而言之，这种代码有风险吗？

In summary, does that this kind of code is risky?

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);

            dispatch_async(queue, ^{

                NSString *fileName = [pathToModel  stringByAppendingPathComponent:[[compDico valueForKey:@"fileName"] lastPathComponent]];

                UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageWithContentsOfFile:
                                                                             fileName]];
                UILabel *label=[[UILabel alloc]initWithFrame:CGRectMake(10, 62, 190, 20)];
                [label setText:[[someArray objectAtIndex:i-1] someText]];
                [label setNumberOfLines:0];
                label.font=[UIFont fontWithName:@"arial" size:10.0f];
                [label setBackgroundColor:[UIColor clearColor]];

                // Create some other view here
                // ...

                dispatch_async(dispatch_get_main_queue(), ^{
                    [self.view addSubview:imageView];
                    [self.view addSubview:label];
                    //Add other view here
                    // ...
                });
            });

感谢您的提前答复！

推荐答案

是的，这是有风险的。

Yes, this is risky. How risky it is only Apple developers can say.

如果文档中说不要使用，那就不要使用。

If the documentation says "don't use it", just don't use it.

请注意，许多UI对象可以（并且确实）使用共享资源。如果您在后台线程中使用它们，则会在共享资源上出现争用条件，一切都会发生。

Note that many UI objects can (and do) use shared resources. If you use them in a background thread, you'll get a race condition on the shared resource and anything can happen.

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