在NSThread上调用时，MKMapView无法加载? [英] MKMapView Not Loading When Called on an NSThread?

问题描述

我正在用一种名为"generateMap"的方法创建一个MKMapView.在viewDidLoad内部，这有效:

I am creating a MKMapView in a method named "generateMap". From inside viewDidLoad, this works:

[self generateMap];

但这会导致地图快速加载然后消失，仅留下空白的灰色网格:

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];

有什么想法为什么当我通过线程调用该方法时会发生这种情况?

Any ideas why this might be happening when I call the method through a thread?

我最终这样做:

-(void)viewDidLoad {
[NSThread detachNewThreadSelector:@selector(spinTheSpinner) toTarget:self withObject:nil];
[self performSelectorOnMainThread:@selector(generateMap) withObject:nil waitUntilDone:NO];
[super viewDidLoad];
}

这使我可以使用微调器(UIActivityIndi​​cator)并根据需要加载MKMapView.我设置为"waitUntilDone:No]"，以便在使用generateMap完成操作之前，屏幕切换MapView.否则，直到generateMap完成，我们才会看到微调器，并且只会看到空白屏幕.

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.

推荐答案

我不建议尝试通过主线程以外的任何方式更新UI.

I don't think it is advisable to try to update the UI through anything but the main thread.

当您尝试使用-performSelectorOnMainThread:withObject:waitUntilDone:在主线程上运行-generateMap时会发生什么?

What happens when you try to run -generateMap on the main thread with -performSelectorOnMainThread:withObject:waitUntilDone:?

例如:

[self performSelectorOnMainThread:@selector(generateMap) withObject:nil waitUntilDone:YES];

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