win10 UWP 标题栏后退

设置里，标题栏有后退按钮

在win平板，可以有后退键，手机也有
pc可以在标题栏

在OnLaunched

//最后
     Windows.UI.Core.SystemNavigationManager.GetForCurrentView().BackRequested += BackRequested;       Windows.UI.Core.SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility = Windows.UI.Core.AppViewBackButtonVisibility.Visible;

BackRequested后退方法