《深入浅出WPF》读书笔记.9Command系统

背景

命令系统是wpf的核心机制之一。

Command系统

命令和路由事件的区别

命令具有约束性，路由事件不具有约束性。

命令的参数

命令关联:用于监测命令，判断命令是否可执行。通过binding可以绑定多个命令。

基础案例

<Window x:Class="CommandDemo.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:CommandDemo"mc:Ignorable="d"Title="MainWindow" Height="450" Width="800"><Grid><StackPanel x:Name="sp1" VerticalAlignment="Center"><TextBox x:Name="tb1" Width="120" Height="40" BorderBrush="Orange" Margin="5"></TextBox><Button x:Name="btn1" Width="120" Height="40" Content="命令执行" Margin="5" ></Button></StackPanel></Grid>
</Window>

using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;namespace CommandDemo
{/// <summary>/// Interaction logic for MainWindow.xaml/// </summary>public partial class MainWindow : Window{public MainWindow(){InitializeComponent();InitializeCommand();}//1.声明并定义命令private RoutedCommand clearCommand = new RoutedCommand("Clear", typeof(MainWindow));private void InitializeCommand(){//将命令赋给命令源(发送者)this.btn1.Command = clearCommand;this.clearCommand.InputGestures.Add(new KeyGesture(Key.C, ModifierKeys.Alt));//指定命令目标this.btn1.CommandTarget = this.tb1;//进行命令关联CommandBinding binding = new CommandBinding();binding.Command = this.clearCommand;binding.CanExecute += Binding_CanExecute;binding.Executed += Binding_Executed;//把命令关联放到外围控件上this.sp1.CommandBindings.Add(binding); }//命令发送到目标后 被调用private void Binding_Executed(object sender, ExecutedRoutedEventArgs e){this.tb1.Text = "";e.Handled = true;}//探测命令是否可以被执行时调用private void Binding_CanExecute(object sender, CanExecuteRoutedEventArgs e){if (this.tb1.Text.Trim() == ""){e.CanExecute = false;}else{e.CanExecute = true;}e.Handled = true;}}
}

自定义命令

从ICommand开始写

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Input;namespace CommandDemo
{public class ClearCommand : ICommand{//当命令执行状态改变时应当被激发public event EventHandler? CanExecuteChanged;//判断是否执行public bool CanExecute(object? parameter){throw new NotImplementedException();}//用于执行public void Execute(object? parameter){IView view=parameter as IView;if (view != null){view.Clear();}}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace CommandDemo
{public  interface IView{bool isChanged { get; set;}void SetBinding();void Clear();void Save();void Refresh();}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;namespace CommandDemo
{/// <summary>/// MyCommandSource.xaml 的交互逻辑/// </summary>public partial class MyCommandSource : UserControl, ICommandSource{public MyCommandSource(){InitializeComponent();}public ICommand Command { get; set; }public object CommandParameter { get; set; }public IInputElement CommandTarget { get; set; }protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e){base.OnMouseLeftButtonDown(e);if (this.CommandTarget != null) { this.Command.Execute(this.CommandTarget);}}}
}

<Window x:Class="CommandDemo.UserDefinedCommandDemo"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:CommandDemo"mc:Ignorable="d"Title="UserDefinedCommandDemo" Height="300" Width="400"><StackPanel><local:MyCommandSource x:Name="myCtrl"><TextBlock Text="自定义命令" Background="AliceBlue" Width="120" TextAlignment="Center"></TextBlock></local:MyCommandSource><local:Miniview x:Name="mv1"></local:Miniview></StackPanel></Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;namespace CommandDemo
{/// <summary>/// UserDefinedCommandDemo.xaml 的交互逻辑/// </summary>public partial class UserDefinedCommandDemo : Window{public UserDefinedCommandDemo(){InitializeComponent();ClearCommand clearCommand = new ClearCommand();this.myCtrl.Command = clearCommand;this.myCtrl.CommandTarget = this.mv1;}}
}