In 14.1 and earlier versions, clicking the custom window will not automatically become the keywindow. Why does 14.2, touching the custom window, it will become the keywindow? @interface DebugWindow : UIWindow @end @implementation DebugWindow (void)makeKeyWindow {   [super makeKeyWindow];   NSLog(@"%s", FUNCTION); } (void)resignKeyWindow {   [super resignKeyWindow];   NSLog(@"%s", FUNCTION); } (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {   [super touchesBegan:touches withEvent:event];   NSLog(@"%s", FUNCTION); } @end @interface ViewController () @property (nonatomic, strong) DebugWindow *window; @end @implementation ViewController (void)viewDidLoad {   [super viewDidLoad];   DebugWindow *window = [[DebugWindow alloc] initWithFrame:self.view.bounds];   window.windowScene = [UIApplication sharedApplication].keyWindow.windowScene;   window.backgroundColor = UIColor.redColor;   window.center = self.view.center;   window.hidden = NO;   self.window = window; } (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {   [super touchesBegan:touches withEvent:event];   NSLog(@"%s", FUNCTION); } @end Why? In 14.1 and earlier versions, clicking the custom window will not automatically become the keywindow. Why does 14.2, touching the custom window, it will become the keywindow?