presentViewController的modalPresentationStyle問題:
首先我們查看一下UIModalPresentationStyle，對比以前的看看有什么變化沒有。發現新增了一個枚舉值UIModalPresentationAutomatic，默認的就是這個，所以才會彈出不是全屏的界面。
typedef NS_ENUM(NSInteger, UIModalPresentationStyle) {
UIModalPresentationFullScreen = 0,
UIModalPresentationPageSheet API_AVAILABLE(ios(3.2)) API_UNAVAILABLE(tvos),
UIModalPresentationFormSheet API_AVAILABLE(ios(3.2)) API_UNAVAILABLE(tvos),
UIModalPresentationCurrentContext API_AVAILABLE(ios(3.2)),
UIModalPresentationCustom API_AVAILABLE(ios(7.0)),
UIModalPresentationOverFullScreen API_AVAILABLE(ios(8.0)),
UIModalPresentationOverCurrentContext API_AVAILABLE(ios(8.0)),
UIModalPresentationPopover API_AVAILABLE(ios(8.0)) API_UNAVAILABLE(tvos),
UIModalPresentationBlurOverFullScreen API_AVAILABLE(tvos(11.0)) API_UNAVAILABLE(ios) API_UNAVAILABLE(watchos),
UIModalPresentationNone API_AVAILABLE(ios(7.0)) = -1,
UIModalPresentationAutomatic API_AVAILABLE(ios(13.0)) = -2,
};
注意：presentViewController默認的UIModalPresentationAutomatic推出新的VC的時候，原VC不會調用viewWillDisappear與viewDidDisappear方法；退出新VC時，原VC不會調用viewWillAppear與viewDidAppear方法。
eg：vcA presentViewController vcB
vcA->vcB：vcA不會調用viewWillDisappear與viewDidDisappear方法；
vcB->vcA：vcA不會調用viewWillAppear與viewDidAppear方法；
如果需要vcA 調用 調用viewWillDisappear與viewDidDisappear 修改modalPresentationStylew為UIModalPresentationFullScreen；