[英]How to trigger KeyUp Event in MVVM using ICommand
我创建了这个简单的视图:
现在,当我在光标位于这两个文本框之一内时按下 RETURN 键时,我希望“Suchen”= SEARCH 按钮触发(KeyUp 事件)。
我知道如何在后面的代码中轻松执行此操作,但我想在 MVVM(在我的视图模型类中)使用 ICommand 执行此操作。 在后面的代码中,我使用了(自动生成的)KeyEventArgs 参数。
我使用 ICommand 在 MVVM 中尝试过,但是 Command 方法给了我一个错误,声称我需要为 KeyEventArgs 参数实例化一个对象。 在后面的代码(非 mvvm 类)中,我不需要实例化任何东西,因为 KeyEventArgs 参数就像方法一样是“自动生成的”。 所以我不必担心。
如何使 KeyUp 事件在我的 MVVM 项目中起作用? 为了回答这个问题,我为您提供了以下缩短的代码:
XAML-视图:
<StackPanel Height="423" VerticalAlignment="Bottom">
<Label Name="lblArtikelbezeichnung" Content="Artikelbezeichnung:" Margin="20, 20, 20, 0"></Label>
<TextBox Name="txtArtikelbezeichnung"
Width="Auto"
Margin="20, 0, 20, 0"
IsEnabled="{Binding BezEnabled}"
Text="{Binding BezText}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="TextChanged">
<i:InvokeCommandAction Command="{Binding TextChangedBez}" />
</i:EventTrigger>
<i:EventTrigger EventName="KeyUp">
<i:InvokeCommandAction Command="{Binding KeyUpBez}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>
<!--TextChanged="txtArtikelbezeichnung_TextChanged"
KeyUp="txtArtikelbezeichnung_KeyUp"-->
<Label Name="lblLieferant" Content="Lieferant:" Margin="20, 0, 20, 0"></Label>
<TextBox Name="txtLieferant"
Width="Auto"
Margin="20, 0, 20, 0"
IsEnabled="{Binding LiefEnabled}"
Text="{Binding LiefText}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="TextChanged">
<i:InvokeCommandAction Command="{Binding TextChangedLief}" />
</i:EventTrigger>
<i:EventTrigger EventName="KeyUp">
<i:InvokeCommandAction Command="{Binding KeyUpLief}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>
<!--TextChanged="txtLieferant_TextChanged"
KeyUp="txtLieferant_KeyUp"-->
<Button Name="btnSuchen"
Content="Suchen"
Width="100" Height="25"
Margin="20, 10,240, 10"
Command="{Binding GefilterteSuche}">
</Button>
...
<StackPanel>
背后的代码:
using System.Windows;
namespace Lieferscheine
{
/// <summary>
/// Interaktionslogik für artikelHinzu.xaml
/// </summary>
public partial class artikelHinzu : Window
{
public artikelHinzu()
{
InitializeComponent();
DataContext = new ArtikelHinzuViewModel();
}
}
}
查看型号:
public class ArtikelHinzuViewModel : INotifyPropertyChanged
{
//ICommands (shortened)
public ICommand GefilterteSuche => new DelegateCommand<object>(SucheArtikel);
public ICommand KeyUpLief => new DelegateCommand<KeyEventArgs>(KeyUpLieferant);
public ICommand KeyUpBez => new DelegateCommand<KeyEventArgs>(KeyUpBezeichnung);
//INotifyPropertyChanged
public event PropertyChangedEventHandler PropertyChanged;
public virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
//Konstruktor
public ArtikelHinzuViewModel()
{
}
//ICommand methods (shortened for reasons of simplicity)
//KeyUp Events (THIS PART IS MY PROBLEM)
private void KeyUpBezeichnung(KeyEventArgs e) //the argument is obligatory but it does not have an instantiated object which is why an error fires...
{
//since I need to create an object for KeyEventArgs I tried this but it is useless...
/*e = new KeyEventArgs(Keyboard.PrimaryDevice,
Keyboard.PrimaryDevice.ActiveSource,
0, Key.Back);
//I need to access this e.Key property but don't know how in my case! That is the actual problem...
if (e.Key == Key.Return)
{
object o = new object();
SucheArtikel(o);
}
*/
}
//same problem here as above...
private void KeyUpLieferant(KeyEventArgs e)
{
/*
e = new KeyEventArgs(Keyboard.PrimaryDevice,
Keyboard.PrimaryDevice.ActiveSource,
0, Key.Back);
if (e.Key == Key.Return)
{
object o = new object();
SucheArtikel(o);
}
*/
}
}
使用InputBindings
更容易:
<TextBox>
<TextBox.InputBindings>
<KeyBinding Key="Enter" Command="{Binding SearchCommand}" />
</TextBox.InputBindings>
</TextBox>
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