Xamarin - 無法使用PopModalAsync

我試圖使用PopModalAsync刪除模態頁面。然而，Navigation.ModalStack.Count爲0。如果我使用PopModalAsync，它會拋出異常：Xamarin - 無法使用PopModalAsync

System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

我使用Xamarin.Forms。下面是一些示例代碼：

App.cs（飲用水）

public class App : Application 
{ 
    public App() 
    { 
     // The root page of your application 
     MainPage = new View.LoginPage(); 
    } 
}

LoginPage.xaml.cs（飲用水）

public partial class LoginPage : ContentPage 
{ 
    public INavigation _Navigate; 
    public LoginPage() 
    { 
     InitializeComponent(); 
     _Navigate = Navigation; 
    } 

    async void LoginBtnClicked(object sender, EventArgs args) 
    { 
     await _Navigate.PushModalAsync(new AuthenicationBrowser()); 
     //await _Navigate.PopModalAsync(); it is work at here 
     Debug.WriteLine("Navigation.NavigationStack LoginBtnClicked ===> {0}", Navigation.NavigationStack.Count); //getting 0 
     Debug.WriteLine("Navigation.ModalStack LoginBtnClicked ===> {0}", Navigation.ModalStack.Count); // getting 1  
    } 

    public async void PopModal() 
    { 
     Debug.WriteLine(Navigation.NavigationStack.Count); 
     await Navigation.PopModalAsync(); 
    } 



}

AuthenicationBrowser.cs（飲用水）*編輯：把PopModalAsync *

public partial class AuthenicationBrowser : ContentPage 
{ 
    public AuthenicationBrowser() 
    { 
     InitializeComponent(); 
    } 
    public async void PopModal() 
    { 
     Debug.WriteLine("Navigation.ModalStack AuthenicationBrowser .PopModal===> {0}", Navigation.ModalStack.Count); // getting 0  
     await Navigation.PopModalAsync(); 
    } 
}

BrowserView.cs（Potable）

個

public class BrowserView : WebView 
{ 
    public BrowserView() 
    { 

    } 
}

AuthenicationBrowserRenderer.cs（Droid的）*編輯：調用PopModal *

[assembly: ExportRenderer(typeof(BrowserView), typeof(AuthenicationBrowserRenderer))] 
namespace App.Droid 
{ 
    class AuthenicationBrowserRenderer : WebViewRenderer 
    { 
     ... // Doing some Auth in OnElementChanged and using JavaScriptCallBack class after received json in Webview 
    } 
    public class JavaScriptCallBack: Java.Lang.Object, IValueCallback 
    { 
     public JavaScriptCallBack() 
     { 

     } 
     public async void OnReceiveValue(Java.Lang.Object result) 
     { 
      Java.Lang.String json = (Java.Lang.String)result; 
      string raw_json = json.ToString(); 
      Debug.WriteLine("raw_json ====>>> {0}", raw_json); 
      var login_page = new LoginPage(); 
      var auth_page = new AuthenicationBrowser(); 

      Debug.WriteLine(login_page.Navigation.ModalStack.Count); // getting 0 
      Debug.WriteLine(auth_page.Navigation.ModalStack.Count); // getting 0 
      auth_page.PopModal(); // Trying to do PopModalAsync 


     } 
    } 
}

來源

2017-02-16 Jacky Shek

裹在一個NavigationPage – Mittchel

的LoginPage我試圖用'=的MainPage新NavigationPage（新View.LoginPage（））;'，但是仍然會導致同樣的結果。我不想在「NavigationPage」中添加它 –

你想彈出Authenticated瀏覽器嗎？您需要替換那裏的流行音樂。 – Mittchel

最後，我可能得到的答案是App.Current.MainPage.Navigation.PopModalAsync();可以做的伎倆。原因是new LoginPage()被稱爲新的Content Page不存在頁面。

如果我從App.Current.MainPage（現有的LoginPage）調用它，它可以從Modal Stack獲取現有模態。

所以溶液可以是：

public partial class LoginPage : ContentPage 
    { 

     public LoginPage() 
     { 
      InitializeComponent(); 

     } 


     async void LoginBtnClicked(object sender, EventArgs args) 
     { 
      await Navigation.PushModalAsync(new AuthenicationBrowser()); 
     } 

     public async void PopModal() 
     { 

      Debug.WriteLine("Navigation.ModalStack PopModal ===> {0}", App.Current.MainPage.Navigation.ModalStack.Count); 
      await App.Current.MainPage.Navigation.PopModalAsync(); 

     } 



    }

來源

2017-02-17 01:58:07

Xamarin - 無法使用PopModalAsync

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