如果使用的是 NSDefaultRunLoopMode ，则 UIAPPlication 会添加运行循环模式 UITrackingRunLoopMode 用于跟踪滚动等滚动视图事件.由于 UIApplication 从 NSDefaultRunLoopMode 切换到 UITrackingRunLoopMode ，因此直到 UIAPPlication 切换回 NSDefaultRunLoopMode .

If you are using NSDefaultRunLoopMode, UIAPPlication adds a run loop mode UITrackingRunLoopMode for tracking scrollview events like scrolling. Since the UIApplication switches from NSDefaultRunLoopMode to UITrackingRunLoopMode any events on NSDefaultRunLoopMode will not be called until UIAPPlication switch back to NSDefaultRunLoopMode.

可能是问题所在，解决方法是将 NSDefaultRunLoopMode 更改为 NSRunLoopCommonModes .

It might be the problem, the fix is change NSDefaultRunLoopMode to NSRunLoopCommonModes .

如果您不确定是否正在使用runloop(如注释中所述).只需在您的项目中搜索 NSDefaultRunLoopMode .

If you are not sure whether you are using runloop or not as you mentioned in comment. Just search NSDefaultRunLoopMode in your project.