C#XAMLUWP-MenuFlyoutItem串列未在MenuFlyoutSubItem中一致更新

這可能是一個簡單的解決方案 - 解釋起來有點長。

我在運行時將自定義串列視圖項添加到 ListView。每個 ListView 項都有一個名稱、一個布林值和一個按鈕。單擊該按鈕時會顯示一個彈出選單，該選單具有如圖所示的子項選單。子專案選單應該只顯示所有其他專案的名稱而不是它本身。正確的行為顯示在第一張圖片中，因為單擊了“專案 4”選單按鈕，我們只看到子選單中列出的專案 0 到 3。

問題是，如果我導航到子選單，然后將新專案添加到串列框中，則新專案永遠不會出現在先前導航到的舊專案的子選單中。如下圖所示，我點擊了第 1 項按鈕，但只列出了第 0 項和第 2 項，出于某種原因，第 3 項和第 4 項沒有列出。

首先，有一個完整的最低 VS2019 解決方案展示了我在GitHub 上描述的行為，盡管我總結了我認為下面代碼的關鍵位。

非樣板 XAML 標頭 (MainPage.Xaml)

xmlns:local="using:DynamicFlyoutMenuTest.ViewModels"

主 ListView 定義及其 DataTemplate 以及在運行時添加 ListView 專案的按鈕：

<StackPanel>
    <Button Name="AddCustomListItemBtn" Click="AddCustomListItemBtn_Click">Add Custom ListItem</Button>
    <ListView
        Name="LayerListBox"
        Height="Auto"
        BorderBrush="{ThemeResource SystemBaseLowColor}"
        BorderThickness="1.0"
        ItemsSource="{x:Bind ViewModel.MyCustomListItems}">
        <ListView.HeaderTemplate>
            <DataTemplate>
                <Grid Padding="2" Background="{ThemeResource SystemBaseLowColor}">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="190" />
                        <ColumnDefinition Width="132" />
                    </Grid.ColumnDefinitions>
                    <TextBlock Style="{ThemeResource CaptionTextBlockStyle}" Text="Name" />
                    <TextBlock
                        Grid.Column="1"
                        Style="{ThemeResource CaptionTextBlockStyle}"
                        Text="Active" />
                </Grid>
            </DataTemplate>
        </ListView.HeaderTemplate>
        <ListView.ItemTemplate>
            <DataTemplate x:Name="TableDataTemplate" x:DataType="local:MyCustomListItem">
                <Grid Height="48" AutomationProperties.Name="{x:Bind ItemName}">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="190" />
                        <ColumnDefinition Width="132" />
                        <ColumnDefinition Width="132" />
                    </Grid.ColumnDefinitions>
                    <TextBlock
                        Grid.Column="0"
                        Padding="10"
                        VerticalAlignment="Center"
                        Text="{x:Bind ItemName, Mode=OneWay}" />
                    <CheckBox
                        Grid.Column="1"
                        VerticalAlignment="Center"
                        IsChecked="{x:Bind isEditing, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
                    <Button
                        Name="exportLayerButton"
                        Grid.Column="2"
                        HorizontalAlignment="Stretch"
                        VerticalAlignment="Center">
                        <Button.Flyout>
                            <MenuFlyout Opening="MenuFlyout_Opening">
                                <MenuFlyoutItem
                                    Name="Action1Btn"
                                    Click="Action1Btn_Click"
                                    Text="Action 1" />
                                <MenuFlyoutItem
                                    Name="Action2Btn"
                                    Click="Action2Btn_Click"
                                    Text="Action 2" />
                                <MenuFlyoutSubItem x:Name="SubActionsBtn" Text="Choose Sub Action">
                                    <MenuFlyoutItem Name="NoSubActionBtn" Text="None" />
                                </MenuFlyoutSubItem>
                            </MenuFlyout>
                        </Button.Flyout>
                        <Polygon
                            Fill="Black"
                            Points="0,0 6,4,0,8"
                            Stroke="Black" />
                    </Button>
                </Grid>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</StackPanel>

MainPage.xaml.cs - 將專案添加到串列并更新彈出子選單項

private void MenuFlyout_Opening(object sender, object e)
{
    //make MenuFlyoutSubItem list all Items in ListView except the one triggering  this function
    var menuFlyout = sender as MenuFlyout;
    // get the menu list we want to add to

    MenuFlyoutSubItem menuSubItems = menuFlyout.Items.Where(x => x.Name == "SubActionsBtn").FirstOrDefault() as MenuFlyoutSubItem;

    // get the active maplayerlistitem (that triggered this menu opening event) 
    MyCustomListItem myCustomListItem = (menuFlyout.Target as Button).DataContext as MyCustomListItem;

    menuSubItems.Items.Clear();
    foreach (var targetItem in ViewModel.MyCustomListItems)
    {
        if (myCustomListItem.ItemName != targetItem.ItemName)
        {
            var tItem = new MenuFlyoutItem();
            tItem.Text = targetItem.ItemName.ToString();
            //tItem.Click  = new Windows.UI.Xaml.RoutedEventHandler(DoSomethingBtn_Click);
            menuSubItems.Items.Add(tItem);
        }
    }
}

private void AddCustomListItemBtn_Click(object sender, Windows.UI.Xaml.RoutedEventArgs e)
{
    // Update ListView
    var newItem = new MyCustomListItem();
    newItem.ItemName = "Item "   ViewModel.MyCustomListItems.Count.ToString();
    newItem.isEditing = false;
    ViewModel.MyCustomListItems.Add(newItem);
}

主視圖模型.cs

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using Microsoft.Toolkit.Mvvm.ComponentModel;

namespace DynamicFlyoutMenuTest.ViewModels
{
    public class MainViewModel : ObservableObject
    {
        public ObservableCollection<MyCustomListItem> MyCustomListItems = new ObservableCollection<MyCustomListItem>();
        public MainViewModel()
        {

        }
    }
    public class MyCustomListItem : INotifyPropertyChanged
    {
        public MyCustomListItem()
        {

        }

        private bool _isEditing;
        public bool isEditing
        {
            get { return _isEditing; }
            set
            {
                _isEditing = value;
                NotifyPropertyChanged(this, "isEditing");
            }
        }

        private string _itemName;
        public string ItemName
        {
            get { return _itemName; }
            set
            {
                _itemName = value;
                NotifyPropertyChanged(this, "ItemName");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void NotifyPropertyChanged(object sender, string propertyName)
        {
            PropertyChangedEventHandler handler = this.PropertyChanged;
            if (handler != null)
            {
                var e = new PropertyChangedEventArgs(propertyName);
                handler(sender, e);
            }
        }
    }
}

編輯您可以在https://www.youtube.com/watch?v=yPNNtsS-n5Q 的視頻中查看該問題 您可以通過以下方式從 GitHub 源中重現該問題

1. 使用“添加...”按鈕將 3 個專案添加到 ListView。
2. 導航到每個 ListViewItem 的 submenuFlyout
3. 使用“添加...”按鈕再添加 2 個串列視圖項
4. 導航到兩個新專案的子選單Flyout，最后
5. 導航到原始 3 個專案的 submenuFlyout 并查看它們尚未更新以反映添加的其他 ListView 專案。

uj5u.com熱心網友回復：

我找到了一種解決方法，方法是洗掉現有的 MenuFlyoutSubItem 并在每次打開 Flyout 時添加一個新的。所以它并不理想，但它確實有效。

如果有人有一個實際的解決方案，我很樂意將其標記為這樣。

否則，這是解決方法：

private void MenuFlyout_Opening(object sender, object e)
        {
            //make MenuFlyoutSubItem list all Items in ListView except the one triggering this function
            var menuFlyout = sender as MenuFlyout;
            // get the menu list we want to add to

            MenuFlyoutSubItem menuSubItems = menuFlyout.Items.Where(x => x.Name == "SubActionsBtn").FirstOrDefault() as MenuFlyoutSubItem;

            // get the active maplayerlistitem (that triggered this menu opening event) 
            MyCustomListItem myCustomListItem = (menuFlyout.Target as Button).DataContext as MyCustomListItem;

            menuFlyout.Items.Remove(menuSubItems);
            menuSubItems = new MenuFlyoutSubItem();
            menuSubItems.Name = "SubActionsBtn";
            menuSubItems.Text = "Choose Sub Action";
            foreach (var targetItem in ViewModel.MyCustomListItems)
             {
                if (myCustomListItem.ItemName != targetItem.ItemName)
                {
                    var tItem = new MenuFlyoutItem();
                    tItem.Text = targetItem.ItemName.ToString();
                    //tItem.Click  = new Windows.UI.Xaml.RoutedEventHandler(DoSomethingBtn_Click);
                    menuSubItems.Items.Add(tItem);              
                }
            }
            menuFlyout.Items.Add(menuSubItems);
        }

標籤：C＃ xml uwp uwp-xml

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