深入浅出WPF--笔记(2015.03.27)

   命令具有一处声明，处处使用的特点。微软在WPF类库中准备了一些便捷的命令库，包括：

（1）、ApplicationCommands;

（2）、ComponentCommands;

（3）、NavigationCommands;

（4）、MediaCommands;

（5）、EditingCommands

都是静态类，而命令就是用这些类的静态只读属性以单件模式暴露出来。

    命令源一定是实现了ICommandSource接口的对象，而ICommandSource有一个属性是CommandParameter.示例如下：

XAML代码：

<Window x:Class="MyTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WPF" Height="240" Width="360">
    <Grid Margin="6">
        <Grid.RowDefinitions>
            <RowDefinition Height="24"/>
            <RowDefinition Height="4"/>
            <RowDefinition Height="24"/>
            <RowDefinition Height="4"/>
            <RowDefinition Height="24"/>
            <RowDefinition Height="4"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <TextBlock Text="Name:" VerticalAlignment="Center" HorizontalAlignment="Left" Grid.Row="0"/>
        <TextBox x:Name="nameTextBox" Margin="60, 0, 0, 0" Grid.Row="0"/>
        <Button Content="New Teacher" Command="New" CommandParameter="Teacher" Grid.Row="2"/>
        <Button Content="New Student" Command="New" CommandParameter="Student" Grid.Row="4"/>
        <ListBox x:Name="listBoxNewItems" Grid.Row="6"/>
    </Grid>
    <Window.CommandBindings>
        <CommandBinding Command="New" CanExecute="New_CanExecute" Executed="New_Executed"/>
    </Window.CommandBindings>
</Window>

 

C#代码：

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void New_CanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            if (string.IsNullOrEmpty(this.nameTextBox.Text))
                e.CanExecute = false;
            else
                e.CanExecute = true;
        }

        private void New_Executed(object sender, ExecutedRoutedEventArgs e)
        {
            string name = this.nameTextBox.Text;
            if (e.Parameter.ToString() == "Teacher")
                this.listBoxNewItems.Items.Add(string.Format("New Teacher: {0},学而不厌，诲人不倦。", name));
            if (e.Parameter.ToString() == "Student")
                this.listBoxNewItems.Items.Add(string.Format("New Student: {0},好好学习，天天向上。", name));
        }
    }

============================================================================

自定义命令示例如下：

XAML代码：

<UserControl x:Class="MyTest.MiniView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             mc:Ignorable="d"
             d:DesignHeight="114" d:DesignWidth="200">
    <Border CornerRadius="5" BorderBrush="LawnGreen" BorderThickness="2">
        <StackPanel>
            <TextBox x:Name="textBox1" Margin="5"/>
            <TextBox x:Name="textBox2" Margin="5, 0"/>
            <TextBox x:Name="textBox3" Margin="5"/>
            <TextBox x:Name="textBox4" Margin="5, 0"/>
        </StackPanel>
    </Border>
</UserControl>

C#代码：

    public partial class MiniView : UserControl, IView
    {
        public MiniView()
        {
            InitializeComponent();
        }

        public bool IsChanged { get; set; }
        public void SetBinding() { }
        public void Refresh() { }
        public void Save() { }
        public void Clear()
        {
            this.textBox1.Clear();
            this.textBox2.Clear();
            this.textBox3.Clear();
            this.textBox4.Clear();
        }
    }

--------------------------------------------------------------------------------------------------------------------------------------

    public interface IView
    {
        bool IsChanged { get; set; }

        void SetBinding();
        void Refresh();
        void Clear();
        void Save();
    }

 

    public class MyCommandSource : UserControl, ICommandSource
    {
        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 (null != this.CommandTarget)
                this.Command.Execute(this.CommandTarget);
        }
    }

 

    public class ClearCommand : ICommand
    {
        public event EventHandler CanExecuteChanged;

        public bool CanExecute(object parameter)
        {
            throw new NotImplementedException();
        }

        public void Execute(object parameter)
        {
            IView view = parameter as IView;
            if (null != view)
                view.Clear();
        }
    }

-------------------------------------------------------------------------------------------------------------------------------

主窗体XAML代码：

<Window x:Class="MyTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:MyTest"
    Title="WPF" Height="205" Width="250">
    <StackPanel>
        <local:MyCommandSource x:Name="ctrlClear" Margin="10">
            <TextBlock Text="清除" FontSize="16" TextAlignment="Center" Background="LightGreen" Width="80"/>
        </local:MyCommandSource>
        <local:MiniView x:Name="miniView"/>
    </StackPanel>
</Window>

 

C#代码：

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            ClearCommand clearCmd = new ClearCommand();
            this.ctrlClear.Command = clearCmd;
            this.ctrlClear.CommandTarget = this.miniView;
        }
    }

==============================================================================

正规的方法是把命令声明在静态全局的地方供所有对象使用。