Xamarin：模态不弹出

Question

几个星期以来，我遇到了一个问题，即提供微调器和标签的模态表单不再弹出。它在旧版本中是运行，但并未更新所有 NuGet 包。知道这是什么吗？有趣的是，它正在处理某些表单而不是其他表单。

protected async override void OnAppearing()
    {
       
        try
        {
            await Navigation.PushModalAsync(new BusyPopUpPage("loading products"));
            
            //ActivityTracker.StartSpinner(true);
            base.OnAppearing();
            IsFiltered = false;
            LblAttributesVisible = false;
            AllProducts = await App.AllProductsController.GetAllProducts();

            grouped = new ObservableCollection<AssortmentGroups>();

            GroupProducts();
            AllProductsListView.IsGroupingEnabled = true;
            AllProductsListView.ItemsSource = grouped;
            await Navigation.PopModalAsync();
        }
        catch (Exception ex)
        {
            await CreateNewBug.CreateANewBug(ex.Message,"Error in Module " + ex.Source,"\nMessage---\n{ 0}" + ex.Message + "\nInnerException---\n{ 0}" + ex.InnerException + "\nStackTrace---\n{ 0}" + ex.StackTrace + "\nTargetSite---\n{ 0}" + ex.TargetSite);
            ToastOptions toastOptions = Message.ShowMessage("An error was raised and a new bug created in our system.", "error");
            await this.DisplayToastAsync(toastOptions);
        }
        
    }

Answer 1

你的逻辑是错误的，因为你的 r 进入了一个无限循环，因为 await Navigation.PopModalAsync();回忆一下你弹出的页面的 OnAppearing。

我为您的加载页面推荐另一种解决方案。而不是 push 和 popModel 创建重叠的页面。然后随时显示和隐藏它们。示例：

 <Grid>
            
            <!--here you can add what u want to display on your page-->
            
            
        <Grid x:Name="LoadingGrid" BackgroundColor="White" IsVisible="false" >
            <StackLayout VerticalOptions="Center" HorizontalOptions="Center">
               
                <ActivityIndicator HeightRequest="50"  Color="#2196F3" IsRunning="True" />
               
            </StackLayout>
        </Grid>
  </Grid>

在你的代码背后

protected async override void OnAppearing()
    {
       
        try
        {
           this.LoadingGrid.IsVisible = true;
            
            //ActivityTracker.StartSpinner(true);
            base.OnAppearing();
            IsFiltered = false;
            LblAttributesVisible = false;
            AllProducts = await App.AllProductsController.GetAllProducts();

            grouped = new ObservableCollection<AssortmentGroups>();

            GroupProducts();
            AllProductsListView.IsGroupingEnabled = true;
            AllProductsListView.ItemsSource = grouped;
            
            this.LoadingGrid.IsVisible = false;
        }
        catch (Exception ex)
        {
            await CreateNewBug.CreateANewBug(ex.Message,"Error in Module " + ex.Source,"\nMessage---\n{ 0}" + ex.Message + "\nInnerException---\n{ 0}" + ex.InnerException + "\nStackTrace---\n{ 0}" + ex.StackTrace + "\nTargetSite---\n{ 0}" + ex.TargetSite);
            ToastOptions toastOptions = Message.ShowMessage("An error was raised and a new bug created in our system.", "error");
            await this.DisplayToastAsync(toastOptions);
        }
        
    }

Answer 2

很奇怪。我将代码缩减为以下内容：

 await Navigation.PushModalAsync(new BusyPopUpPage("loading products"));
            LoopCounter++;
            //base.OnAppearing();
            //IsFiltered = false;
            //LblAttributesVisible = false;
            //AllProducts = await App.AllProductsController.GetAllProducts();

            //grouped = new ObservableCollection<AssortmentGroups>();

            //GroupProducts();
            //AllProductsListView.IsGroupingEnabled = true;
            //AllProductsListView.ItemsSource = grouped;
            await Navigation.PopModalAsync();
            await DisplayAlert("Info", "LoopCounter=" + LoopCounter, "OK");

所以，我们只有 PushModalAsync 和 PopModalAsync。当前所有其他代码不运行ning。我加了一个loop-counter因为我看到代码是运行ning 2次。如果我运行带有 PopModalAsync 的代码，它会运行整个代码中的 2 次。如果我删除 PopModalAsync，它仅通过代码运行s 1 次。也许这就是问题所在。我也会继续测试

Answer 3

Amjad Saab 解决了这个问题！我不知道，但在旧版本的 Xamarin Forms 中这似乎有所不同。问题正如 Amjad 所说：如果我在 onAppearing 中使用 PopModalAsync，它会重新启动 OnAppearing 的覆盖并在循环中结束。我将代码更改为以下内容：`

public AllProductsListPage()
    {
        InitializeComponent();
        LoadData();
    }
    protected async void LoadData()
    {
        try
        {

            await Navigation.PushModalAsync(new BusyPopUpPage("loading products"));
            base.OnAppearing();
            IsFiltered = false;
            LblAttributesVisible = false;
            AllProducts = await App.AllProductsController.GetAllProducts();
            grouped = new ObservableCollection<AssortmentGroups>();
            GroupProducts();
            AllProductsListView.IsGroupingEnabled = true;
            AllProductsListView.ItemsSource = grouped;
            await Navigation.PopModalAsync();
        }
        
        catch (Exception ex)
        {
            await CreateNewBug.CreateANewBug(ex.Message,"Error in Module " + ex.Source,"\nMessage---\n{ 0}" + ex.Message + "\nInnerException---\n{ 0}" + ex.InnerException + "\nStackTrace---\n{ 0}" + ex.StackTrace + "\nTargetSite---\n{ 0}" + ex.TargetSite);
            ToastOptions toastOptions = Message.ShowMessage("An error was raised and a new bug created in our system.", "error");
            await this.DisplayToastAsync(toastOptions);
        }
    }

所以我所做的是：

我将“覆盖 OnAppearing”函数的名称更改为 LoadData()。所以没有OnAppearing功能了
运行 InitializeComponent() 之后直接来自页面的 LoadData() 函数

`

Xamarin：模态不弹出

Xamarin: Modal from not popping

xamarin

xamarin.forms