c# - 任何时候都只能打开一个ContentDialog

如果我多次按下登录按钮，则会触发消息：“异步操作未正确启动。任何时候都只能打开一个ContentDialog。” （延迟表示该应用与服务器联系以查看用户是否有效所花费的时间。）

如果我使用MessageDialog，一切正常，但是我想使用ContentDialog提供的额外自定义设置。

This链接没有帮助。下面的代码示例向我展示了如何尝试使用它。

XAML：

<Page
    x:Class="DuckTracker.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:DuckTracker"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition></RowDefinition>
            <RowDefinition></RowDefinition>
            <RowDefinition></RowDefinition>
        </Grid.RowDefinitions>

        <Grid.ColumnDefinitions>
            <ColumnDefinition></ColumnDefinition>
            <ColumnDefinition></ColumnDefinition>
        </Grid.ColumnDefinitions>

        <TextBlock Grid.Row="0" Grid.Column="0" Height="20">Name:</TextBlock>
    <TextBox Grid.Row="0" Grid.Column="1" Height="20"></TextBox>
    <Button Click="Button_Click" Grid.Row="2" VerticalAlignment="Bottom">Login</Button>
    </Grid>
</Page>

后面的代码：

using System;
using System.Threading.Tasks;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace DuckTracker
{

    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        private async void Button_Click(object sender, RoutedEventArgs e)
        {
            bool canLogin = await CanLogin();

            if (canLogin == false)
            {
                try
                {
                     await AlertWithMessages("Fail", "Could not log in!", "ok");

                }
                catch (Exception ex)
                {

                    var dialog = new Windows.UI.Popups.MessageDialog(ex.Message, "Error");
                    await dialog.ShowAsync();
                }

            }
        }

        public async Task AlertWithMessages(string title, string msg, string confirm)
        {
            ContentDialog dialog = new ContentDialog()
            {
                Title = title,
                Content = msg,
                PrimaryButtonText = confirm
            };

            await ContentDialogMaker.CreateContentDialogAsync(dialog, true);

        }

        public async Task<bool> CanLogin()
        {
            await Task.Delay(1000);

            return false;
        }
    }
}

从上述链接借来的代码：

using System;
using System.Threading.Tasks;
using Windows.UI.Xaml.Controls;

namespace DuckTracker
{
    public static class ContentDialogMaker
    {
        public static async void CreateContentDialog(ContentDialog Dialog, bool awaitPreviousDialog) { await CreateDialog(Dialog, awaitPreviousDialog); }
        public static async Task CreateContentDialogAsync(ContentDialog Dialog, bool awaitPreviousDialog) { await CreateDialog(Dialog, awaitPreviousDialog); }

        static async Task CreateDialog(ContentDialog Dialog, bool awaitPreviousDialog)
        {
            if (ActiveDialog != null)
            {
                if (awaitPreviousDialog)
                {
                    await DialogAwaiter.Task;
                    DialogAwaiter = new TaskCompletionSource<bool>();
                }
                else ActiveDialog.Hide();
            }
            ActiveDialog = Dialog;
            ActiveDialog.Closed += ActiveDialog_Closed;
            await ActiveDialog.ShowAsync();
            ActiveDialog.Closed -= ActiveDialog_Closed;
        }

        public static ContentDialog ActiveDialog;
        static TaskCompletionSource<bool> DialogAwaiter = new TaskCompletionSource<bool>();
        private static void ActiveDialog_Closed(ContentDialog sender, ContentDialogClosedEventArgs args) { DialogAwaiter.SetResult(true); }
    }
}

我将DoingStuff添加到Button_Click（）中，可以防止出现错误消息，但是我认为必须有更好的方法：

private async void Button_Click(object sender, RoutedEventArgs e)
{
    if (DoingStuff == false)
    {
        DoingStuff = true;

        bool canLogin = await CanLogin();

        if (canLogin == false)
        {
            try
            {

                await AlertWithMessages("Fail", "Could not log in!", "ok");

            }
            catch (Exception ex)
            {

                var dialog = new Windows.UI.Popups.MessageDialog(ex.Message, "Error");
                await dialog.ShowAsync();
            }

        }

        DoingStuff = false;
    }
}

最佳答案

通常，启动登录方法时，需要同时启用登录按钮，以避免多次单击。您的解决方案也可用，直到显示上一个对话框后该按钮才起作用。

并且我创建了new ContentDialogMaker。有关更多信息，请参考以下内容。

public static class ContentDialogMaker
{
    public static async void CreateContentDialog(ContentDialog Dialog, bool awaitPreviousDialog) { await CreateDialog(Dialog, awaitPreviousDialog); }
    public static async Task CreateContentDialogAsync(ContentDialog Dialog, bool awaitPreviousDialog) { await CreateDialog(Dialog, awaitPreviousDialog); }

    static async Task CreateDialog(ContentDialog Dialog, bool awaitPreviousDialog)
    {
        if (ActiveDialog != null)
        {
            if (awaitPreviousDialog)
            {
                ActiveDialog.Hide();
            }
            else
            {
                switch (Info.Status)
                {
                    case AsyncStatus.Started:
                        Info.Cancel();
                        break;
                    case AsyncStatus.Completed:
                        Info.Close();
                        break;
                    case AsyncStatus.Error:

                        break;
                    case AsyncStatus.Canceled:

                        break;
                }
            }
        }
        ActiveDialog = Dialog;
        ActiveDialog.Closing += ActiveDialog_Closing;
        Info = ActiveDialog.ShowAsync();
    }
    public static IAsyncInfo Info;
    private static void ActiveDialog_Closing(ContentDialog sender, ContentDialogClosingEventArgs args)
    {
        ActiveDialog = null;
    }

    public static ContentDialog ActiveDialog;
}

唯一的区别是ActiveDialog是在ActiveDialog_Closing事件处理程序方法中清空的。并且可以确保显示后将清除先前的对话框。因此，只有一个ContentDialog将同时打开。