Question

我使用Xamarin Forms并且我遇到问题时使用InsertPageBefore（）方法和Pages的现有对象。

这是我的观看代码：

private FirstPage firstPage; 
private SecondPage secondPage = new SecondPage();
private ThirdPage thirdPage = new ThirdPage(); 
private async void ItemSelectedMethod()
{
        var root = App.NavigationPage.Navigation.NavigationStack[0];
        if (SelectedItem == Items[0])
        {
            if (!IsFirstChoose)
            {
                App.NavigationPage.Navigation.InsertPageBefore(firstPage, root);
                await App.NavigationPage.PopToRootAsync(false);
            }
        }
        if (SelectedItem == Items[1])
        {
            App.NavigationPage.Navigation.InsertPageBefore(secondPage, root);
            await App.NavigationPage.PopToRootAsync(false);
        }
        if (SelectedItem == Items[2])
        {
            App.NavigationPage.Navigation.InsertPageBefore(thirdPage, root);
            await App.NavigationPage.PopToRootAsync(false);
        }

        IsFirstChoose = false;
        rootPageViewModel.IsPresented = false;
}

它抛出异常＆＃34; System.ArgumentException：＆＃39;无法插入已存在于导航堆栈中的页面＆＃39;＆＃34;。如何在页面的现有对象之间切换？我不想在InsertPageBefore（）中创建新对象。在调用InsertPageBefore（）：

之前，我尝试使用它代码

foreach (var item in App.NavigationPage.Navigation.NavigationStack.ToList())
                App.NavigationPage.Navigation.RemovePage(item);

但是它不起作用......任何人都可以帮助我吗？

Answer 1

它没有与UWP合作。这里有适合你的解决方法，但你真的需要阅读如何使用Master-Detail页面。

public partial class App : Application
    {
        public static RootPage RootPage { get; private set; } //DON'T DO THIS, 
                                                              //FIND A BETTER WAY 
        public App()
        {
            InitializeComponent();

            RootPage = new RootPage();
            MenuPage menuPage = new MenuPage(RootPage.vm);

            RootPage.Master = menuPage;
            RootPage.Detail = new NavigationPage(new MainPage());// NavigationPage;
            MainPage = RootPage;
        }

        protected override void OnStart()
        {
            // Handle when your app starts
        }

        protected override void OnSleep()
        {
            // Handle when your app sleeps
        }

        protected override void OnResume()
        {
            // Handle when your app resumes
        }
    }

然后

private async void ItemSelectedMethod()
        {

            if (SelectedItem == Items[0])
            {
                App.RootPage.Detail = new NavigationPage(mainPage);
            }
            if (SelectedItem == Items[1])
            {
                App.RootPage.Detail = new NavigationPage(secondPage);
            }
            if (SelectedItem == Items[2])
            {
                App.RootPage.Detail = new NavigationPage(thirdPage);
            }
            rootPageViewModel.IsPresented = false;
        }

如何使用Xamarin.Forms.INavigation.InsertPageBefore在页面之间切换

1 个答案: