应用场景
我现在做一个系统登录功能，要求在PasswordBox上输完密码后回车，能够响应Enter事件，并执行ViewModel中对应的方法。如果登录成功则隐藏当前窗口显示主窗体，登录失败则焦点返回到用户名TextBox中，并全选文字，方便用户再重新输入。
这个在我们制造业自动化流程控制中，做防呆功能是很明显的，因为没有人为去参与。
如果像Winform一样的开发模式，就相对很简单了，现在是要在ViewModel，对一个初学者来说就相对地困难多了,那怎么办呢？
设计思想
自定义一个Command,支持多参数对象数组，把控件，事件传到ViewModel中。
实现步骤
- 自定义命令InteractiveCommand类，继承TriggerAction<DependencyObject>
// -----------------------------------------------------------------------
// <copyright file="InteractiveCommand.cs" company="">
// TODO: Update copyright text.
// </copyright>
// ----------------------------------------------------------------------- namespace TLAgent.SecurityManager.WPF
{
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Input;
using System.Windows.Interactivity;
using System.Reflection; /// <summary>
/// TODO: Update summary.
/// </summary>
public class InteractiveCommand : TriggerAction<DependencyObject>
{
protected override void Invoke(object parameter)
{
if (base.AssociatedObject != null)
{
ICommand command = this.ResolveCommand();
object[] tempObj = { parameter, CommandParameter };
if ((command != null) && command.CanExecute(tempObj))
{
command.Execute(tempObj);
}
}
} public object CommandParameter
{
get { return GetValue(CommandParameterProperty); }
set { SetValue(CommandParameterProperty, value); }
} public static readonly DependencyProperty CommandParameterProperty = DependencyProperty.Register
("CommandParameter", typeof(object), typeof(InteractiveCommand), new PropertyMetadata(null, OnCommandParameterChanged)); private static void OnCommandParameterChanged
(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
InteractiveCommand ic = sender as InteractiveCommand;
if (ic != null)
{
ic.SynchronizeElementState();
}
} private void SynchronizeElementState()
{
ICommand command = Command;
if (command != null)
{
FrameworkElement associatedObject = AssociatedObject as FrameworkElement;
if (associatedObject != null)
{
associatedObject.IsEnabled = command.CanExecute(CommandParameter);
}
}
} private ICommand ResolveCommand()
{
ICommand command = null;
if (this.Command != null)
{
return this.Command;
}
if (base.AssociatedObject != null)
{
foreach (PropertyInfo info in base.AssociatedObject.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
if (typeof(ICommand).IsAssignableFrom(info.PropertyType) && string.Equals(info.Name, this.CommandName, StringComparison.Ordinal))
{
command = (ICommand)info.GetValue(base.AssociatedObject, null);
}
}
}
return command;
} private string commandName;
public string CommandName
{
get
{
base.ReadPreamble();
return this.commandName;
}
set
{
if (this.CommandName != value)
{
base.WritePreamble();
this.commandName = value;
base.WritePostscript();
}
}
} #region Command
public ICommand Command
{
get { return (ICommand)GetValue(CommandProperty); }
set { SetValue(CommandProperty, value); }
}
public static readonly DependencyProperty CommandProperty =
DependencyProperty.Register("Command", typeof(ICommand), typeof(InteractiveCommand), new UIPropertyMetadata(null));
#endregion
}
}
2. 在XAML中做绑定，把EventName定为”KeyDown“，请参考如下代码：
<PasswordBox x:Name="txtPassword" Height="23" Helper:PasswordBoxHelper.Attach="True" Helper:PasswordBoxHelper.Password="{Binding Path=AuthUser.Password,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Left" Margin="101,92,0,0" VerticalAlignment="Top" Width="178" TabIndex="2">
<i:Interaction.Triggers>
<i:EventTrigger EventName="KeyDown">
<Helper:InteractiveCommand Command="{Binding EnterLoginCommand}" CommandName="EnterLoginCommand" CommandParameter="{Binding ElementName=txtUserName}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</PasswordBox>3. 后台的Command声明为DelegateCommand<object[]><object[]><object[]><object[]> _CommandWithEventArgs,并实例化，同时绑定一个带参数object[]的用户验证方法:
public ICommand EnterLoginCommand
{
get { return _CommandWithEventArgs ?? (_CommandWithEventArgs = new DelegateCommand<object[]>(CheckUser)); }
}
绑定的方法为CheckUser,如下
private void CheckUser(object[] objs)
{
KeyEventArgs e = objs[0] as KeyEventArgs;
if (e.Key == Key.Enter)
{
object obj = objs[1];
VerifyUser(obj);
}
}
private void VerifyUser(object objParam)
{
if (AuthUser.UserName != null && AuthUser.Password != null)
{
if (AuthUser.UserName.ToUpper().Equals("AGAN") && AuthUser.Password.Equals("123"))
{
IsVisibility = Visibility.Hidden;
SplashScreen splashScreen = new SplashScreen("Images/SplashScreen.JPG");
splashScreen.Show(true);
MainWindow window = new MainWindow();
window.ShowDialog();
}
else
{
MessageBox.Show(@"用户名或密码错误!");
TextBox txtUserName = (TextBox)objParam;
txtUserName.Focus();
txtUserName.SelectAll();
}
}
else
{
MessageBox.Show(@"用户名或密码不能为空!");
TextBox txtUserName = (TextBox)objParam;//转换为TextBox,即为View层的txtUserName控件
txtUserName.Focus();//获取焦点
txtUserName.SelectAll();//全选文本
}
}
测试
运行程序后，输入用户密码，显示如图：