我正在开发一款专用于 Windows 的 MAUI C# 应用程序。这款应用程序的独特之处在于它与本地数据库配合使用，并调用填充服务器上数据库的 API。在此应用程序中，我有一个 p...

我正在开发一款专用于 Windows 的 MAUI C# 应用程序。这款应用程序的独特之处在于它与本地数据库配合使用，并调用一个 API 来填充服务器上的数据库。在此应用程序中，我有一个显示项目列表的页面。在此页面上，我还有一些按钮，允许我添加/更新/删除此列表中的项目。这些按钮会调出一个用于更新或添加项目的模式。

当我单击其中一个按钮时，模态框出现，然后我进行更改。由于模态框的背景是透明的，我可以看到修改已应用于列表。但是，模态框不会像代码中预期的那样自动关闭。我必须单击“退出”才能使模态框消失。

返回列表后，如果我想再次与列表交互，我会单击其中一个按钮。模式打开，我执行操作（添加/更新），我看到修改正在进行，但模式没有关闭并冻结。如果我单击“退出”，我会收到此错误：Application.Current.MainPage.Navigation.ModalStack.Count = 0，并且应用程序崩溃。

如果我将按钮中的所有逻辑都注释掉，我也会遇到同样的问题。

我尝试了很多方法，但我觉得我在主线程管理中明显缺少了一些东西。我不太了解 MAUI 中的线程。有人能帮我吗？

提前致谢。

这是我的代码，其中我的列表的视图

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="FntrAudit.Views.RequiredDisplayPage"
             Title="Affichage Obligatoire">
    <Grid RowDefinitions="Auto,*,Auto"
       ColumnDefinitions="*,*,*">
        <Label Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="3" Text="Affichages obligatoires" FontSize="Large"></Label>

        <ListView Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="3" ItemsSource="{Binding RequiredDisplays}">
            <ListView.ItemTemplate>
                <DataTemplate >
                    <ViewCell>
                        <StackLayout Orientation="Horizontal" VerticalOptions="Center" Spacing="10">
                            <CheckBox IsChecked="{Binding IsOk}"  VerticalOptions="Center"/>
                            <Label Text="{Binding Intitule}" VerticalOptions="Center" HorizontalOptions="FillAndExpand" LineBreakMode="WordWrap"/>
                            <ImageButton Clicked="UpdateDoc" HeightRequest="20" WidthRequest="20" Source="update.png" CommandParameter="{Binding .}"></ImageButton>
                            <ImageButton Clicked="Delete_Clicked" HeightRequest="20" WidthRequest="20" Source="delete.png" CommandParameter="{Binding .}"></ImageButton>
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
        <Button   BackgroundColor="#AE1439" Grid.Row="2" Grid.Column="1"  Text="Enregistrer et revenir à l'audit" Margin="5" Clicked="Record_Clicked" HorizontalOptions="Fill"></Button>
        <Button   BackgroundColor="#AE1439" Grid.Row="2" Grid.Column="0"  Text="Ajouter document obligatoire" Margin="5" Clicked="AddDoc" HorizontalOptions="Fill"></Button>
    </Grid>
</ContentPage>

背后的代码

using FntrAudit.DALApi;
using FntrAudit.Data;
using FntrAudit.Models;
using FntrAudit.Utils;
using FntrAudit.Views.Modal;
using Microsoft.EntityFrameworkCore;
using System.Collections.ObjectModel;

namespace FntrAudit.Views;

public partial class RequiredDisplayPage : ContentPage
{
    private Audit _audit;
    SqliteDbContext _db = new SqliteDbContext();
    private ObservableCollection<RequiredDisplay> requiredDisplays;
    private RestService<RequiredDisplay> _requiredDisplayService = new RestService<RequiredDisplay>();
    private RestService<LogFromApp> _LogService = new RestService<LogFromApp>();
    public ObservableCollection<RequiredDisplay> RequiredDisplays
    {
        get { return requiredDisplays; }
        set
        {
            if (requiredDisplays != value)
            {
                requiredDisplays = value;
                OnPropertyChanged(nameof(RequiredDisplays));
            }
        }
    }
    public RequiredDisplayPage(Audit audit)
    {
        InitializeComponent();
        _audit = audit;
        InitializeAsync();
    }
    private async void InitializeAsync()
    {
        await LoadRequiredDoc();
    }

    public async Task LoadRequiredDoc()
    {
        try
        {
            Console.WriteLine("Loading required documents...");
            bool hasWeb = Connectivity.Current.NetworkAccess == NetworkAccess.Internet;
            List<RequiredDisplay> requiredDisplays = new List<RequiredDisplay>();


            if (_audit.RequiredDisplay.Any(rd => rd.IsOk))
            {
                RequiredDisplays = new ObservableCollection<RequiredDisplay>(_audit.RequiredDisplay);
            }
            else
            {
                RequiredDisplays = new ObservableCollection<RequiredDisplay>(_audit.RequiredDisplay);

            }

            await Task.Delay(1000);
            this.BindingContext = this;
            Console.WriteLine("Required documents loaded successfully.");
        }
        catch(Exception ex)
        {
            var t = ex.Message;
            Console.WriteLine($"Error loading required documents: {ex.Message}");
        }
      
    }

    private async void Delete_Clicked(object sender, EventArgs e)
    {
        try
        {
            bool answer = await DisplayAlert("Supprimer un document obligatoire", "Êtes-vous sûr de vouloir supprimer ce document ?", "Oui", "Non");

            if (answer)
            {
                if (sender is ImageButton button && button.CommandParameter is RequiredDisplay toDelete)
                {
                    try
                    {
                        Console.WriteLine($"Attempting to delete document: {toDelete.GuidRDisplay}");
                        _db.RequiredDisplay.Remove(toDelete);
                        await _db.SaveChangesAsync();
                        await _requiredDisplayService.DeleteTodoItemAsync(toDelete.GuidRDisplay, Constantes.URLAPI + "RequiredDisplay/");
                        RequiredDisplays.Remove(toDelete);
                        Console.WriteLine($"Document {toDelete.GuidRDisplay} deleted successfully.");
                    }
                    catch (DbUpdateConcurrencyException)
                    {
                        await _db.Entry(toDelete).ReloadAsync();
                        await DisplayAlert("Échec de la suppression", "Le document a été modifié ou supprimé par une autre transaction. Veuillez réessayer.", "OK");
                        Console.WriteLine($"Concurrency error while deleting document: {toDelete.GuidRDisplay}");
                    }
                    catch (Exception ex)
                    {
                        LogFromApp logFromApp = new LogFromApp()
                        {
                            DateCreation = DateTime.Now,
                            Intitule = "ModalRequired delete doc (UserContext ContextCurrent) " + ex.Message,
                            Trace = ex.ToString(),
                            UserInvolved = " "
                        };

                        await _LogService.Create(logFromApp, Constantes.URLAPILOG, true);
                        await DisplayAlert("Erreur", "Une erreur est survenue lors de la suppression du document.", "OK");
                        Console.WriteLine($"Error deleting document: {ex.Message}");
                    }
                }
            }
        }
        catch (Exception ex)
        {
            await DisplayAlert("Erreur", "Une erreur est survenue lors de la suppression du document.", "OK");
            Console.WriteLine("Erreur lors de la suppression du document : " + ex.Message);
        }
    }

    //public async void Delete_Clicked(object sender, EventArgs e)
    //{
    //    bool answer = false;
    //    try
    //    {
    //         answer = await DisplayAlert("Supprimer un document obligatoire", "Êtes-vous sûr de vouloir supprimer ce document ?", "Oui", "Non");
    //    }
    //    catch(Exception ex)
    //    {
    //        var toto = ex.Message;
    //    }

    //    if (answer)
    //    {
    //        if (sender is ImageButton button && button.CommandParameter is RequiredDisplay toDelete)
    //        {
    //            try
    //            {
    //                _db.RequiredDisplay.Remove(toDelete);
    //                _db.SaveChanges();
    //                await _requiredDisplayService.DeleteTodoItemAsync(toDelete.GuidRDisplay, Constantes.URLAPI + "RequiredDisplay/");
    //                RequiredDisplays.Remove(toDelete);
    //            }
    //            catch (DbUpdateConcurrencyException ex)
    //            {
    //                // Option 1: Raffraîchir l'entité depuis la base de données
    //                await _db.Entry(toDelete).ReloadAsync();

    //                // Afficher un message d'erreur à l'utilisateur
    //                await DisplayAlert("Échec de la suppression", "Le document a été modifié ou supprimé par une autre transaction. Veuillez réessayer.", "OK");

    //                // Option 2: Tentative de réexécution de la suppression après rechargement
    //                // _db.RequiredDisplay.Remove(toDelete);
    //                // _db.SaveChanges();
    //            }
    //            catch (Exception ex)
    //            {
    //                // Afficher un message d'erreur générique
    //                await DisplayAlert("Erreur", "Une erreur est survenue lors de la suppression du document.", "OK");
    //            }
    //        }
    //    }
    //}
    public async void Record_Clicked(object sender, EventArgs e)
    {
        try
        {
            Console.WriteLine("Recording clicked.");
            _audit.RequiredDisplay = RequiredDisplays.ToList();
            await Application.Current.MainPage.Navigation.PopModalAsync();
            Console.WriteLine("Modal closed successfully.");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error in Record_Clicked: {ex.Message}");
        }
    }
    public async void AddDoc(object sender, EventArgs e)
    {
        try
        {
            RequiredDisplay requiredDisplay = new RequiredDisplay();
            var modal = new ModalRequiredDisplay(requiredDisplay, true);
            modal.RequiredDisplays = this.RequiredDisplays;
            //  await Application.Current.MainPage.Navigation.PushModalAsync(modal);

            var tcs = new TaskCompletionSource<bool>();
            modal.Disappearing += async (s, args) =>
            {
                Console.WriteLine("Modal disappearing...");
                if (!tcs.Task.IsCompleted)
                {
                    tcs.SetResult(true);
                }

            };
            await Application.Current.MainPage.Navigation.PushModalAsync(modal);
            await tcs.Task;  // Wait for the modal to close
            await LoadRequiredDoc();
        }
        catch(Exception ex)
        {
            Console.WriteLine($"Error in AddDoc: {ex.Message}");
        }
       
       
    }

    public async void UpdateDoc(object sender, EventArgs e)
    {
        try
        {
            if (sender is ImageButton button && button.CommandParameter is RequiredDisplay toUpdate)
            {
                var modal = new ModalRequiredDisplay(toUpdate, false);
                modal.RequiredDisplays = this.RequiredDisplays;

                var tcs = new TaskCompletionSource<bool>();
                modal.Disappearing += (s, args) =>
                {
                    Console.WriteLine("Modal disappearing...");
                    if (!tcs.Task.IsCompleted)
                    {
                        tcs.SetResult(true);
                    }
                };

                await Application.Current.MainPage.Navigation.PushModalAsync(modal);
                Console.WriteLine("Modal pushed to stack.");
                await tcs.Task;  // Wait for the modal to close
                Console.WriteLine("Modal closed.");
                await LoadRequiredDoc();
            }
        
        }catch(Exception ex)
        {
            var t = ex.Message;
        }
    }
}

情态动词

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="FntrAudit.Views.Modal.ModalRequiredDisplay"
             BackgroundColor="#00000000"
             Title="Affichage Obligatoire">
    <ContentView HorizontalOptions="Center" VerticalOptions="Center">
        <ScrollView>
            <Frame BackgroundColor="White" CornerRadius="20" Padding="20"
               HorizontalOptions="Center" VerticalOptions="Center"
               WidthRequest="700" HeightRequest="600">
           
            <VerticalStackLayout Spacing="15">
                <Label Text="{Binding TitleModal}" TextColor="Black" FontSize="24" FontAttributes="Bold" HorizontalOptions="Center"></Label>

                <Editor Text="{Binding Intitule}" Placeholder="Intitulé du document" AutoSize="TextChanges"></Editor>

                <VerticalStackLayout Spacing="10">
                    <Label Text="Effectif de l'entreprise concernée (si besoin)" VerticalOptions="CenterAndExpand" FontAttributes="Bold"/>
                    <VerticalStackLayout Spacing="5">
                        <Grid ColumnDefinitions="Auto,*,Auto" RowDefinitions="Auto" Padding="5">
                            <Label Text="Toutes" Grid.Column="0" VerticalOptions="CenterAndExpand" Margin="0,0,10,0"/>
                            <RadioButton x:Name="All" GroupName="Effectif" IsChecked="True" Grid.Column="2" VerticalOptions="CenterAndExpand"/>
                        </Grid>
                        <Grid ColumnDefinitions="Auto,*,Auto" RowDefinitions="Auto" Padding="5">
                            <Label Text="de 1 à 10" Grid.Column="0" VerticalOptions="CenterAndExpand" Margin="0,0,10,0"/>
                            <RadioButton x:Name="Has1SalOrMore" GroupName="Effectif" IsChecked="{Binding Has1SalOrMore}" Grid.Column="2" VerticalOptions="CenterAndExpand"/>
                        </Grid>
                        <Grid ColumnDefinitions="Auto,*,Auto" RowDefinitions="Auto" Padding="5">
                            <Label Text="de 11 à 50" Grid.Column="0" VerticalOptions="CenterAndExpand" Margin="0,0,10,0"/>
                            <RadioButton x:Name="Has11SalOrMore" GroupName="Effectif" IsChecked="{Binding Has11SalOrMore}" Grid.Column="2" VerticalOptions="CenterAndExpand"/>
                        </Grid>
                        <Grid ColumnDefinitions="Auto,*,Auto" RowDefinitions="Auto" Padding="5">
                            <Label Text="de 51 à 300" Grid.Column="0" VerticalOptions="CenterAndExpand" Margin="0,0,10,0"/>
                            <RadioButton x:Name="Has50SalOrMore" GroupName="Effectif" IsChecked="{Binding Has50SalOrMore}" Grid.Column="2" VerticalOptions="CenterAndExpand"/>
                        </Grid>
                        <Grid ColumnDefinitions="Auto,*,Auto" RowDefinitions="Auto" Padding="5">
                            <Label Text="de 301 à 1000" Grid.Column="0" VerticalOptions="CenterAndExpand" Margin="0,0,10,0"/>
                            <RadioButton x:Name="Has300SalOrMore" GroupName="Effectif" IsChecked="{Binding Has300SalOrMore}" Grid.Column="2" VerticalOptions="CenterAndExpand"/>
                        </Grid>
                        <Grid ColumnDefinitions="Auto,*,Auto" RowDefinitions="Auto" Padding="5">
                            <Label Text="1000 et plus" Grid.Column="0" VerticalOptions="CenterAndExpand" Margin="0,0,10,0"/>
                            <RadioButton x:Name="Has1000SalOrMore" GroupName="Effectif" IsChecked="{Binding Has1000SalOrMore}" Grid.Column="2" VerticalOptions="CenterAndExpand"/>
                        </Grid>
                    </VerticalStackLayout>
                </VerticalStackLayout>

                <HorizontalStackLayout Spacing="10">
                    <Button BackgroundColor="#007AFF" TextColor="White" Text="Enregistrer" Margin="5" Clicked="AddDoc_Clicked" HorizontalOptions="FillAndExpand"></Button>
                    <Button BackgroundColor="#FF3B30" TextColor="White" Text="Quitter" Margin="5" Clicked="Quit_Clicked" HorizontalOptions="FillAndExpand"></Button>
                </HorizontalStackLayout>
            </VerticalStackLayout>
        </Frame>
        </ScrollView>
    </ContentView>
</ContentPage>

背后的代码

using CommunityToolkit.Maui.Alerts;
using FntrAudit.DALApi;
using FntrAudit.Data;
using FntrAudit.Models;
using FntrAudit.Services;
using FntrAudit.Utils;
using Microsoft.EntityFrameworkCore;
using System.Collections.ObjectModel;

namespace FntrAudit.Views.Modal;

public partial class ModalRequiredDisplay : ContentPage
{
    private RequiredDisplay _document;
    private bool _isCreation;
    SqliteDbContext _db = new SqliteDbContext();
    private ObservableCollection<RequiredDisplay> requiredDisplays;
    private RestService<RequiredDisplay> _requiredDisplayService = new RestService<RequiredDisplay>();
    private RestService<LogFromApp> _LogService = new RestService<LogFromApp>();
    
    public ObservableCollection<RequiredDisplay> RequiredDisplays
    {
        get { return requiredDisplays; }
        set
        {
            if (requiredDisplays != value)
            {
                requiredDisplays = value;
                OnPropertyChanged(nameof(RequiredDisplays));

            }
        }
    }
    public ModalRequiredDisplay(RequiredDisplay document, bool isCreation)
    {
        InitializeComponent();
        _document = document;
        _isCreation = isCreation;
        
        _document.TitleModal = _isCreation ? "Ajout d'un document obligatoire" : "Mise à jour d'un document obligatoire";
       
        this.BindingContext = _document;     
    }

    private async void Delete_Clicked(object sender, EventArgs e)
    {
        await CloseModalAsync();
    }

    private async void Quit_Clicked(object sender, EventArgs e)
    {
        await CloseModalAsync();
    }

   

    private async Task AddDoc(object sender, EventArgs e)
    {
        bool hasWeb = Connectivity.Current.NetworkAccess == NetworkAccess.Internet;
       
        try
        {
            if (_isCreation)
            {

                RequiredDisplay required = new RequiredDisplay();
                _document.IsOk = false;
                _document.AuditId = 1;
                _document.GuidRDisplay = Guid.NewGuid().ToString();

                await _db.RequiredDisplay.AddAsync(_document);
                await _db.SaveChangesAsync();

                Func<Task> saveDocument = async () =>
                {
                    await _requiredDisplayService.Create(_document, Constantes.URLAPI + "RequiredDisplay", true);
                };

                if (hasWeb)
                {
                    await saveDocument.Invoke();
                }
                else
                {
                    var connectivityService = new ConnectivityService();
                    connectivityService.AddTask(saveDocument);
                }
            }
            else
            {
                _db.Update(_document);
                await _db.SaveChangesAsync();

                Func<Task> updateDocument = async () =>
                {
                    await _requiredDisplayService.Create(_document, Constantes.URLAPI + "RequiredDisplay/RequiredDisplay/" + _document.GuidRDisplay, false);
                };

                if (hasWeb)
                {
                    await updateDocument.Invoke();
                }
                else
                {
                    var connectivityService = new ConnectivityService();
                    connectivityService.AddTask(updateDocument);
                }

            }
           
            await ShowToasterAsync("Document obligatoire enregistré avec succès.");
        }
        catch (Exception ex)
        {
            LogFromApp logFromApp = new LogFromApp()
            {
                DateCreation = DateTime.Now,
                Intitule = "ModalRequired (UserContext ContextCurrent) " + ex.Message,
                Trace = ex.ToString(),
                UserInvolved = " "
            };

            await _LogService.Create(logFromApp, Constantes.URLAPILOG, true);
        }
        finally
        {
            try
            {
                if (RequiredDisplays == null)
                {
                    RequiredDisplays = new ObservableCollection<RequiredDisplay>();
                }

                RequiredDisplay requiredDisplay = null;

                if (RequiredDisplays.Count > 0 && _document != null)
                {
                    requiredDisplay = RequiredDisplays.FirstOrDefault(rd => rd.GuidRDisplay == _document.GuidRDisplay);
                }

                if (requiredDisplay != null)
                {
                    int index = RequiredDisplays.IndexOf(requiredDisplay);
                    if (index != -1)
                    {
                        RequiredDisplays[index] = _document;
                    }
                }

                await CloseModalAsync();
            }
            catch (Exception closeEx)
            {
                Console.WriteLine("Erreur lors de la fermeture de la modal : " + closeEx.Message);
            }

        }
    }

    private async Task CloseModalAsync()
    {
        try
        {
            if (Application.Current.MainPage.Navigation.ModalStack.Count > 0)
            {
                await Application.Current.MainPage.Navigation.PopModalAsync();
                Console.WriteLine("Modal closed successfully.");
            }
            else
            {
                Console.WriteLine("Modal stack is empty.");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error in CloseModalAsync: {ex.Message}");
        }
    }


    private async void DeleteDoc(object sender, EventArgs e)
    {
        bool answer = await DisplayAlert("Supprimer un document obligatoire", "Êtes-vous sûr de vouloir supprimer ce document ?", "Oui", "Non");

        if (answer)
        {
            if (sender is ImageButton button && button.CommandParameter is RequiredDisplay toDelete)
            {
                try
                {
                    _db.RequiredDisplay.Remove(toDelete);
                    await _db.SaveChangesAsync();
                    await _requiredDisplayService.DeleteTodoItemAsync(toDelete.GuidRDisplay, Constantes.URLAPI + "RequiredDisplay/");
                    RequiredDisplays.Remove(toDelete);
                }
                catch (DbUpdateConcurrencyException ex)
                {
                    // Option 1: Raffraîchir l'entité depuis la base de données
                    await _db.Entry(toDelete).ReloadAsync();

                    // Afficher un message d'erreur à l'utilisateur
                    await DisplayAlert("Échec de la suppression", "Le document a été modifié ou supprimé par une autre transaction. Veuillez réessayer.", "OK");

                    // Option 2: Tentative de réexécution de la suppression après rechargement
                    // _db.RequiredDisplay.Remove(toDelete);
                    // _db.SaveChanges();
                }
                catch (Exception ex)
                {
                    LogFromApp logFromApp = new LogFromApp()
                    {
                        DateCreation = DateTime.Now,
                        Intitule = "ModalRequired delete doc (UserContext ContextCurrent) " + ex.Message,
                        Trace = ex.ToString(),
                        UserInvolved = " "
                    };

                    await _LogService.Create(logFromApp, Constantes.URLAPILOG, true);
                    // Afficher un message d'erreur générique
                    await DisplayAlert("Erreur", "Une erreur est survenue lors de la suppression du document.", "OK");
                }
            }
        }
    }
    private async Task ShowToasterAsync(string message)
    {
        var toast = Toast.Make(message);
        await toast.Show();
    }

    public async void AddDoc_Clicked(object sender, EventArgs e)
    {
        await AddDoc(sender, e);
    }
   
}