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D G
Asked: 2024-12-23 02:35:03 +0800 CST

选择一个条目应该会改变标签的文本，但事实并非如此

  • 772

我有一个标签和两个条目。我想让标签显示所选条目。现在选择第二个条目不会更改标签。罪魁祸首是什么？

这是我的代码。

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:vm="clr-namespace:MyProject"
             x:Class="MyProject.TestPage"
             x:DataType="vm:TestViewModel"
             Title="TestPage">
    <VerticalStackLayout>
        <Entry x:Name="Entry1"  Text="Entry 1">
            <Entry.GestureRecognizers>
                <TapGestureRecognizer Command="{Binding SetSelectedEntryCommand}"
                                      CommandParameter="{Reference Entry1}" />
            </Entry.GestureRecognizers>
        </Entry>
        <Entry x:Name="Entry2"
               Text="Entry 2">
            <Entry.GestureRecognizers>
                <TapGestureRecognizer Command="{Binding SetSelectedEntryCommand}"
                                      CommandParameter="{Reference Entry2}" />
            </Entry.GestureRecognizers>
        </Entry>
  
        <Label Text="{Binding SelectedEntry.Text}" />
    </VerticalStackLayout>
</ContentPage>

public partial class TestPage : ContentPage
{
    public TestPage(TestViewModel model)
    {
        InitializeComponent();
        BindingContext = model;
        model.InitializeCommand.Execute(Entry1);
    }
}

这很烦人：看起来你的帖子大部分都是代码；请添加更多详细信息。

public partial class TestViewModel : ObservableObject
{
    [ObservableProperty]
    Entry _selectedEntry;

    [RelayCommand]
    void Initialize(Entry selectedEntry)
    {
        SelectedEntry = selectedEntry;
        SelectedEntry.BackgroundColor = Colors.Pink;
    }

    [RelayCommand]
    void SetSelectedEntry(Entry selectedEntry)
    {
        SelectedEntry.BackgroundColor = Colors.White;
        SelectedEntry = selectedEntry;
        SelectedEntry.BackgroundColor = Colors.Pink;
    }
}

编辑

显然它在 Android 上可以运行，但在 Windows 上却不行。因为我需要在 Windows 上使用触摸屏？

maui

3 个回答

  1. 您应该使用带有 EventToCommandBehavior 的 Focused 事件

    <Label Text="Whatever is your label text" x:Name="TxtLabel"/>
<Entry x:Name="MyButton">
        <Entry.Behaviors>
            <toolkit:EventToCommandBehavior
                EventName="Focused"
                Command="{Binding YourCommand}" 
                CommandParameter="{Binding Text, Source={x:Reference TxtLabel}}"/>
        </Entry.Behaviors>
    </Entry>

    更多信息请查看：

    https://learn.microsoft.com/en-us/dotnet/maui/user-interface/controls/entry?view=net-maui-9.0

    https://learn.microsoft.com/en-us/dotnet/communitytoolkit/maui/behaviors/event-to-command-behavior

    • 1

  2. 这是我的解决方案。我更改了代码。-----更新-----

    在这里我使用了EventToCommandBehavior，并且它成功了！

    测试视图模型

    
  public class TestViewModel : INotifyPropertyChanged
  {
      public event PropertyChangedEventHandler PropertyChanged;
      public void OnPropertyChanged([CallerMemberName] string name = "") =>
     PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
      public string Text1 { get => text; set {
              if (text != value) {
                  text = value;
                  OnPropertyChanged();  
              }
          } }

      public string text;
      public TestViewModel() {
          SetSelectedEntryCommand = new Command<Entry>((obj) =>
          {
              SelectedEntry.BackgroundColor = Colors.White;
              SelectedEntry = obj;
              SelectedEntry.BackgroundColor = Colors.Pink;
          }
          )
         ;
      }
    public ICommand SetSelectedEntryCommand { set; get; }
    Entry SelectedEntry { get =>entry; set {
              if (entry != value) {
                  entry = value;
                  Text1 = entry.Text;      
              }
          } }

      Entry entry;
      public void Initialize(Entry selectedEntry)
      {
          SelectedEntry = selectedEntry;
          SelectedEntry.BackgroundColor = Colors.Pink;
      }
  }

    测试页面

       public TestPage(TestViewModel model)
    {
        InitializeComponent();
        BindingContext = model;
        model.Initialize(Entry1);
    }

    测试页面

           <VerticalStackLayout>
           <Entry x:Name="Entry1" Text="Entry 1" TextColor="Red">
               <Entry.Behaviors>
                   <toolkit:EventToCommandBehavior  
                       EventName="Focused"
                       Command="{Binding SetSelectedEntryCommand}"
                       CommandParameter="{Reference Entry1}"
                       
                       />
               </Entry.Behaviors>
           </Entry>
           <Entry x:Name="Entry2"  TextColor="Red" 
Text="Entry 2">
               <Entry.Behaviors>
                   <toolkit:EventToCommandBehavior  
           EventName="Focused"
           Command="{Binding SetSelectedEntryCommand}"
           CommandParameter="{Reference Entry2}"                      
           />
               </Entry.Behaviors>
           </Entry>
           <Label Text="{Binding Text1}" />
       </VerticalStackLayout>
    • 1
  3. Best Answer

    @FreakyAli 的答案的一个变体，您可以绑定到 IsFocused 属性并在 DataTrigger 中使用它，如下所示。这将最大限度地减少视图模型需要做的工作量，因为您可以仅在视图中实现所有要求，例如

    <VerticalStackLayout Padding="30,0" Spacing="25">
    <Entry x:Name="Entry1" Text="Entry 1" />
    <Entry x:Name="Entry2" Text="Entry 2" />
    <Label x:DataType="Entry" Text="{Binding Text, Source={Reference Entry1}}">
        <Label.Triggers>
            <DataTrigger
                x:DataType="Entry"
                Binding="{Binding IsFocused, Source={Reference Entry2}}"
                TargetType="Label"
                Value="True">
                <Setter x:DataType="Entry" Property="Text" Value="{Binding Text, Source={Reference Entry2}}" />
            </DataTrigger>
        </Label.Triggers>
    </Label>
</VerticalStackLayout>

    我确实有一个 CommunityToolkit MultiMathExpressionConverter 增强功能，它有一个简单的 XAML 解决方案，可以帮助您解决日益扩大的规模问题，例如针对 3 个输入字段：

    <VerticalStackLayout Padding="30,0" Spacing="25">
    <Entry x:Name="Entry1" Text="Entry 1" />
    <Entry x:Name="Entry2" Text="Entry 2" />
    <Entry x:Name="Entry3" Text="Entry 3" />
    <Label Text="{MultiBinding {Binding Text, Source={Reference Entry1}},
                               {Binding IsFocused, Source={Reference Entry2}},
                               {Binding Text, Source={Reference Entry2}},
                               {Binding IsFocused,Source={Reference Entry3}},
                               {Binding Text, Source={Reference Entry3}},
                               Converter={StaticResource MultiMathExpressionConverter},
                               ConverterParameter='x1 and x2 or x2 and x3 or x0'}" />
</VerticalStackLayout>

    以上内容基于能够将 Label.Text 表达式写为：

    Label.Text = Entry2.IsFocused && Entry2.Text
          || Entry3.IsFocused && Entry3.Text
          || Entry1.Text

    或者你可以做一些更常规的事情，例如ConverterParameter='x1 ? x2 : x3 ? x4 : x0'：

     Label.Text = Entry2.IsFocused
               ? Entry2.Text
               : Entry3.IsFocused
                 ? Entry3.Text
                 : Entry1.Text

    通过投票来帮助我：

    • 1

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