按钮命令选择列表框中的下一个/上一个项目

Question

是否有一个简单的命令我可以发送到一个标准的WPF列表框使用一个按钮，它会让它选择列表中的下一个/上一个项目？

目前我与这个解决方案滚动：

  <Button Width="30" Height="30" x:Name="PreviousButton"> 
       <i:Interaction.Triggers> 
        <i:EventTrigger EventName="Click"> 
         <ei:ChangePropertyAction Increment="True" 
               PropertyName="SelectedIndex" 
               TargetName="MyListBox" 
               Value="-1" /> 
        </i:EventTrigger> 
       </i:Interaction.Triggers> 
      </Button> 
      <!-- ListBox would be here. --> 
      <Button Width="30" Height="30" x:Name="NextButton"> 
       <i:Interaction.Triggers> 
        <i:EventTrigger EventName="Click"> 
         <ei:ChangePropertyAction Increment="True" 
               PropertyName="SelectedIndex" 
               TargetName="MyListBox" 
               Value="1" /> 
        </i:EventTrigger> 
       </i:Interaction.Triggers> 
      </Button> 

这很好。如果您在列表中的第一个项目上（与上一个项目相同）点击上一个按钮，则确实会导致异常，但是当前计划是告诉它在禁用按钮时，如果selectedindex是第一个/最后一个项目列表。

我在问这个问题只是为了看看我是否错过了一个技巧。 “不，这是不可能的，你必须以另一种方式去做”是一个完全可以接受的答案，如果是这样的话。

Answer 1

使用mvvm会更好，更简单。这是我将如何解决它。请注意我的示例代码使用mvvmLight工具包。

查看

<Window x:Class="*1.MainWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
     xmlns:local="clr-namespace:*1" 
     xmlns:viewModel="clr-namespace:*1.ViewModel" 
     mc:Ignorable="d" 
     Title="MainWindow" Height="350" Width="525"> 

    <Window.Resources> 
     <viewModel:MainViewModel x:Key="MainViewModel"/> 
    </Window.Resources> 
    <Grid DataContext="{StaticResource MainViewModel}"> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="*"/> 
      <RowDefinition Height="Auto"/> 
     </Grid.RowDefinitions> 

     <ListBox Grid.Row="0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" ItemsSource="{Binding Students}" x:Name="ListBox" 
       SelectedIndex="{Binding SelectedIndex}"/> 
     <StackPanel Orientation="Horizontal" Grid.Row="1"> 
      <Button Content="Next" Width="50" Height="24" Command="{Binding NextCommand}" CommandParameter="{Binding ElementName=ListBox,Path=SelectedIndex}"/> 
      <Button Content="Previous" Width="50" Height="24" Command="{Binding PreviousCommand}" CommandParameter="{Binding ElementName=ListBox,Path=SelectedIndex}"/> 
     </StackPanel> 
    </Grid> 
</Window> 

视图模型

using System.Collections.Generic; 
using System.Collections.ObjectModel; 
using System.Windows.Input; 
using GalaSoft.MvvmLight; 
using GalaSoft.MvvmLight.CommandWpf; 

namespace *1.ViewModel 
{ 

    public class MainViewModel : ViewModelBase 
    { 

     public MainViewModel() 
     { 
     NextCommand=new RelayCommand<int>(OnNext,CanNext); 
     PreviousCommand=new RelayCommand<int>(OnPrevious,CanPrevious); 
      SelectedIndex = 0; 

      foreach (var student in GetStudent()) 
      { 
       _students.Add(student); 
      } 
     } 

     public ICommand NextCommand { get; set; } 
     public ICommand PreviousCommand { get; set; } 
     private int _selectedIndex; 


     private List<Student> GetStudent() 
     { 
      return new List<Student>() 
      { 
       new Student {Id = 0,Name = "Kwame0"}, 
       new Student {Id = 0,Name = "Kwame1"}, 
       new Student {Id = 0,Name = "Kwame2"}, 
       new Student {Id = 0,Name = "Kwame3"}, 
        new Student {Id = 0,Name = "Kwame4"}, 
       new Student {Id = 0,Name = "Kwame5"}, 
       new Student {Id = 0,Name = "Kwame6"}, 
       new Student {Id = 0,Name = "Kwame7"}, 
        new Student {Id = 0,Name = "Kwame8"}, 
       new Student {Id = 0,Name = "Kwame9"}, 
       new Student {Id = 0,Name = "Kwame10"}, 
       new Student {Id = 0,Name = "Kwame11"}, 
        new Student {Id = 0,Name = "Kwame12"}, 
       new Student {Id = 0,Name = "Kwame13"}, 
       new Student {Id = 0,Name = "Kwame14"}, 
       new Student {Id = 0,Name = "Kwame15"}, 
      }; 
     } 
     public int SelectedIndex 
     { 
      get { return _selectedIndex; } 
      set { _selectedIndex = value;RaisePropertyChanged(()=>SelectedIndex); } 
     } 


     private ObservableCollection<Student> _students=new ObservableCollection<Student>(); 

     public ObservableCollection<Student> Students 
     { 
      get { return _students; } 
      set { _students = value; } 
     } 


     private void OnNext(int index) 
     { 
      if (SelectedIndex != Students.Count) 
       SelectedIndex += 1; 
      else 
      { 
       SelectedIndex = 0; 
      } 
     } 

     private bool CanNext(int indext) 
     { 
      return SelectedIndex != Students.Count; 
     } 

     private void OnPrevious(int index) 
     { 
      if (SelectedIndex != 0) 
       SelectedIndex -= 1; 
      else 
      { 
       SelectedIndex = Students.Count; 
      } 
     } 

     private bool CanPrevious(int index) 
     { 
      return SelectedIndex != 0; 
     } 

    } 

    public class Student 
    { 
     public int Id { get; set; } 
     public string Name { get; set; } 

     public override string ToString() 
     { 
      return $"{Id}-{Name}"; 
     } 
    } 
} 

Answer 2

对于它没有“标准”命令，只需创建NextItemCommand和PrevItemCommand即可更改int value;，您可以绑定到ListBox.SelectedIndex，这将是您想要的。关于enable \ disable按钮只是为每个命令传递Enabled方法，因此它会检查，value可以更改。