1.iOS13獲取keywindow,不推薦使用 [UIApplication sharedApplication].keyWindow，過(guò)期了，

@property(nullable, nonatomic,readonly) UIWindow *keyWindow API_DEPRECATED("Should not be used for applications that support multiple scenes as it returns a key window across all connected scenes", ios(2.0, 13.0));

需要使用

[UIApplication sharedApplication].windows[0];

2.present一個(gè)控制器后的keywindow，和頁(yè)面前的，不一定是一個(gè)window。需要頁(yè)面展示完成獲取當(dāng)前頁(yè)的主窗口，進(jìn)行操作。

//iOS13下面不推薦的方法
[self presentViewController:navContoller animated:YES completion:NULL];
 UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
//不一定是頁(yè)面展示完成的window，故view不一定展示
[keyWindow addSubview:view];

//推薦的做法
[self presentViewController:navContoller animated:YES completion:^{
UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
[keyWindow addSubview:view];
 }];

。。。待續(xù)