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我正在将应用程序转换为使用非 MVVM 格式的 FreshMVVM。当应用程序启动时，有一个登录页面，然后在登录后，一个带有从每个标签页上的按钮调用的模式页面的标签页。

鉴于我正在遵循的过程，我认为这将是使用 Michael Ridland 的过程来切换 NavigationStacks 的完美选择（https://github.com/rid00z/FreshMvvm#switching-out-navigationstacks-on-the-xamarinforms -mainpage )，但是这些步骤似乎缺少很多重要的说明，并且这些步骤不在 GitHub 上的示例应用程序中。

在我的App.xaml.xs文件中，我有以下代码：

public App()
        {
            InitializeComponent();
            var loginPage = FreshMvvm.FreshPageModelResolver.ResolvePageModel<LoginPageModel>();
            var loginContainer = new STNavigationContainer(loginPage, NavigationContainerNames.AuthenticationContainer);
            var homePageViewContainer = new FreshTabbedNavigationContainer(NavigationContainerNames.MainContainer);

            MainPage = loginContainer;
        }

        public FreshTabbedNavigationContainer(string navigationServiceName)
        {
            NavigationServiceName = navigationServiceName;
            RegisterNavigation();
        }

        protected void RegisterNavigation()
        {
            FreshIOC.Container.Register<IFreshNavigationService>(this, NavigationServiceName)
        }

        public void SwitchOutRootNavigation(string navigationServiceName)
        {
            IFreshNavigationService rootNavigation =
                FreshIOC.Container.Resolve<IFreshNavigationService>(navigationServiceName);
        }
        public void LoadTabbedNav()
        {
            var tabbedNavigation = new FreshTabbedNavigationContainer();
            tabbedNavigation.AddTab<CharactersPageModel>("Characters", "characters.png");
            tabbedNavigation.AddTab<AdventuresPageModel>("Adventures", "adventures.png");
            tabbedNavigation.AddTab<AccountPageModel>("Account", "account.png");
            MainPage = tabbedNavigation;
        }
 public class NavigationContainerNames
    {
        public const string AuthenticationContainer = "AuthenticationContainer";
        public const string MainContainer = "MainContainer";
    }

这似乎与 ReadMe.md 中提供的步骤相匹配，但是NavigationServiceName返回错误的调用，因为没有关于创建这样一个类或它应该包含什么的说明，我也不清楚FreshTabbedNavigationContainerorSwitchOutRootNavigation将被调用的位置。

有没有人能让这个工作？我在这方面缺少哪些步骤？

编辑：我忘记了我已经扩展了FreshNavigationContainter课程和FreshNavigationPage课程。这是我的扩展课程：

STNavigationContainer：

public class STNavigationContainer : FreshNavigationContainer
    {
        public STNavigationContainer(Page page) : base(page)
        {
        }

        public STNavigationContainer(Page page, string navigationPageName) : base(page, navigationPageName)
        {
        }

        protected override Page CreateContainerPage(Page page)
        {
            if (page is NavigationPage || page is MasterDetailPage || page is TabbedPage)
                return page;

            return new STNavigationPage(page);
        }
    }

ST导航页：

public class STNavigationPage : NavigationPage
    {
        public STNavigationPage()
        {
                
        }

        public STNavigationPage(Page page) : base(page)
        {
            BarBackgroundColor = Color.FromHex("#2DAFEB");
            BarTextColor = Color.FromHex("#C9371D");
        }
    }

编辑 2：重新阅读https://michaelridland.com/xamarin/implementing-freshmvvm-mvvm-xamarin-forms/和 Github 帖子，我发现我需要在自定义导航服务中执行此操作，所以这是我更新的代码。

应用程序.xaml.cs：

    public partial class App : Application
    {
        public static Account account = new Account();

        public App()
        {
            InitializeComponent();
            FreshIOC.Container.Register<IDatabaseService, DatabaseService>();

            if (account.Equals(null))
            {
                LoadSingleNav();
            }
            else
            {
                LoadTabbedNav();
            }

            var navPage = new NavigationPage(new LoginPage())
            {
                BarBackgroundColor = Color.FromHex("#2DAFEB"),
                BarTextColor = Color.FromHex("#C9371D")
            };
            NavigationPage.SetHasNavigationBar(navPage.CurrentPage, false);
            MainPage = navPage;

            MainPage = loginContainer;
        }

        public FreshTabbedNavigationContainer(string navigationServiceName)
        {
            NavigationContainerNames = navigationServiceName;
            RegisterNavigation();
        }

        protected override void OnStart()
        {
        }

        protected override void OnSleep()
        {
        }

        protected override void OnResume()
        {
        }
    }

CustomNavService.cs：

    public class CustomNavService : NavigationPage, IFreshNavigationService
    {
        FreshTabbedNavigationContainer _tabbedNavigationPage;
        Page _charactersPage, _adventuresPage, _accountPage;
        public CustomNavService(Page page) : base (page)
        {
            NavigationServiceName = "CustomNavService";
            LoadTabbedNav();
            CreateLoginPage();
            RegisterNavigation();
        }

        public string NavigationServiceName { get; private set; }

        public void NotifyChildrenPageWasPopped()
        {
            throw new NotImplementedException();
        }

        public async Task PopPage(bool modal = false, bool animate = true)
        {
            if (modal)
                await Navigation.PopModalAsync (animate);
            else
                await Navigation.PopAsync (animate);
        }

        public async Task PopToRoot(bool animate = true)
        {
            await Navigation.PopToRootAsync(animate);
        }

        public async Task PushPage(Page page, FreshBasePageModel model, bool modal = false, bool animate = true)
        {
            if (modal)
                await Navigation.PushModalAsync(page, animate);
            else
                await Navigation.PushAsync(page, animate);
        }

        public Task<FreshBasePageModel> SwitchSelectedRootPageModel<T>() where T : FreshBasePageModel
        {
            IFreshNavigationService rootNavigation =
                FreshIOC.Container.Resolve<IFreshNavigationService>(NavigationServiceName);
        }

        public void LoadTabbedNav()
        {
            _tabbedNavigationPage = new FreshTabbedNavigationContainer();
            _charactersPage = _tabbedNavigationPage.AddTab<CharactersPageModel>("Characters", "characters.png");
            _adventuresPage = _tabbedNavigationPage.AddTab<AdventuresPageModel>("Adventures", "adventures.png");
            _accountPage = _tabbedNavigationPage.AddTab<AccountPageModel>("Account", "account.png");
            this = _tabbedNavigationPage;
        }
        private void CreateLoginPage()
        {
            var loginPage = FreshPageModelResolver.ResolvePageModel<LoginPageModel>(null);
            var loginContainer = new STNavigationContainer(loginPage, CustomNavService.NavigationContainerNames.AuthenticationContainer);
            var homePageViewContainer = new FreshTabbedNavigationContainer(CustomNavService.NavigationContainerNames.MainContainer);

        }

        protected void RegisterNavigation()
        {
            FreshIOC.Container.Register<IFreshNavigationService>(this, NavigationServiceName);
        }

        public class NavigationContainerNames
        {
            public const string AuthenticationContainer = "AuthenticationContainer";
            public const string MainContainer = "MainContainer";
        }

    }

我的自定义导航服务中的SwitchSelectedRootPageModel<T>任务显示需要返回，我不太清楚LoadTabbedNav应该包含什么this；该示例显示this.Detail，但这显示为无效参考。

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1 回答 1

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通过我们的 FreshMvvm 实现，我们的 SwitchSelectedRootPageModel 看起来像这样：

public Task<FreshBasePageModel> SwitchSelectedRootPageModel<T>() where T : FreshBasePageModel
{
    return Task.FromResult<FreshBasePageModel>(null);
}

我们的代码正确使用

this.Detail = _tabbedNavigationPage;

所以如果你得到一个无效的参考，肯定还有其他东西丢失。

于 2021-07-30T13:37:55.193 回答