在 NSThread 上调用时 MKMapView 未加载？
我正在名为“generateMap”的方法中创建 MKMapView。从 viewDidLoad 内部，这是可行的：
[self generateMap];
但这会导致地图快速加载然后消失，只留下空白的灰色网格：
[NSThread detachNewThreadSelector:@selector(generateMap) toTarget:self withObject:nil];
有什么想法为什么当我通过线程调用该方法时可能会发生这种情况？
我最终这样做了：
-(void)viewDidLoad {
[NSThread detachNewThreadSelector:@selector(spinTheSpinner) toTarget:self withObject:nil];
[self performSelectorOnMainThread:@selector(generateMap) withObject:nil waitUntilDone:NO];
[super viewDidLoad];
}
这允许我有一个微调器（UIActivityIndicator）并根据需要加载 MKMapView。我设置了“waitUntilDone:No]”，以便屏幕在使用generateMap完成之前切换MapView。否则，我们将看不到微调器，并且只会看到空白屏幕，直到生成映射完成为止。
I am creating a MKMapView in a method named "generateMap". From inside viewDidLoad, this works:
[self generateMap];
but this causes the map to quickly load and then disappear, leaving only the blank grey grid:
[NSThread detachNewThreadSelector:@selector(generateMap) toTarget:self withObject:nil];
Any ideas why this might be happening when I call the method through a thread?
I ended up doing this:
-(void)viewDidLoad {
[NSThread detachNewThreadSelector:@selector(spinTheSpinner) toTarget:self withObject:nil];
[self performSelectorOnMainThread:@selector(generateMap) withObject:nil waitUntilDone:NO];
[super viewDidLoad];
}
This allows me to have a spinner (UIActivityIndicator) and load the MKMapView as I want. I set "waitUntilDone:No]" so that the screen switches the MapView before it is done with generateMap. Otherwise, we would not see the spinner and would only see a blank screen until generateMap was done.
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评论（2）
我认为不建议尝试通过主线程以外的任何方式更新 UI。
当您尝试使用
-performSelectorOnMainThread:withObject:waitUntilDone:在主线程上运行-generateMap时会发生什么？例如：
I don't think it is advisable to try to update the UI through anything but the main thread.
What happens when you try to run
-generateMapon the main thread with-performSelectorOnMainThread:withObject:waitUntilDone:?For example:
首先，我可以看到
generateMap方法吗？其次，执行选择器的更充分的方法是说First off, can I see the
generateMapmethod? Second, a more sufficient way to perform a selector is by saying