使用GCD在后台创建UIKit对象是一种不好的做法吗?
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!
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.