Windows Presentation Foundation (WPF)中的命令(Commands)简述

原文:Windows Presentation Foundation (WPF)中的命令(Commands)简述

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萝卜鼠在线图形图像处理
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在我们日常的应用程序操作中,经常要处理各种各样的命令和进行相关的事件处理,比如需要复制、粘贴文本框中的内容;上网查看网页时,可能需要返回上一网页查看相应内容;而当我们播放视频和多媒体时,我们可能要调节音量,快速拖动到我们想看的片段等等。在Winform编程中,我们经常使用各种各样的控件来解决此类问题,当然我们也必须编写一堆代码来处理各种各样的命令和事件处理。那么,Windows Presentation Foundation (WPF)作为微软新一代图形图像支援系统,它是如何处理这些命令及事件的呢?

在WPF中,许多控件都自动集成了固有的命令集。比如文本框TextBox就提供了复制(Copy),粘贴(Paste),裁切(Cut),撤消(Undo)和重做(Redo)命令等。

WPF提供常用应用程序所用的命令集,常用的命令集包括:ApplicationCommands, ComponentCommands, NavigationCommands, MediaCommands和EditingCommands

ApplicationCommands(应用程序命令):
 CancelPrint:取消打印
 Close:关闭
 ContextMenu:上下文菜单
 Copy:复制
 CorrectionList: Gets the value that represents the Correction List command. 
 Cut:剪切
 Delete:删除
 Find:查找
 Help:帮助
 New:新建
 NotACommand:不是命令,被忽略
 Open:打开
 Paste:粘贴
 Print:打印
 PrintPreview:打印预览
 Properties:属性
 Redo:重做
 Replace:取代
 Save:保存
 SaveAs:另存为
 SelectAll:选择所有的
 Stop:停止
 Undo:撤消

ComponentCommands(组件命令):
 ExtendSelection:后接Down/Left/Right/Up, 比如:ExtendSelectionDown(Shift+Down,Extend Selection Down),ExtendSelectionLeft等
 Move:后接Down/Left/Right/Up, 如:MoveDown
 MoveFocus:后接Down/Forward/Back/Up, 如:MoveFocusDown
 MoveFocusPage:后接Down/Up,如:MoveFocusPageUp
 MoveTo:后接End/Home/PageDown/PageUp,比如:MoveToPageDown
 ScrollByLine
 ScrollPage:后接Down/Left/Right/Up,比如:ScrollPageLeft
 SelectTo:End/Home/PageDown/PageUp,比如:SelectToEnd

NavigationCommands(导航命令):
 Browse浏览: 后接Back/Forward/Home/Stop, 比如:BrowseBack
 缩放显示:DecreaseZoom, IncreaseZoom, Zoom
 Favorites(收藏)
 页面:FirstPage, LastPage, PreviousPage, NextPage,GoToPage
 NavigateJournal
 Refresh(刷新)
 Search(搜索)

MediaCommands(多媒体控制命令):
 Treble高音:DecreaseTreble,IncreaseTreble
 Bass低音:BoostBass,DecreaseBass,IncreaseBass
 Channel频道:ChannelDown,ChannelUp
 MicrophoneVolume麦克风音量调节:DecreaseMicrophoneVolume,IncreaseMicrophoneVolume,MuteMicrophoneVolume
 ToggleMicrophoneOnOff:麦克风开关
 Volume音量: DecreaseVolume,IncreaseVolume,MuteVolume
 Rewind, FastForward(回放,快进)
 Track轨道:PreviousTrack,NextTrack [上一段(节)]
 Play,Pause,Stop,Record(播放,暂停,停止,录制)
 TogglePlayPause
 Select选择

EditingCommands(编辑/排版类命令):
 Align对齐:AlignCenter,AlignJustify,AlignLeft,AlignRight(居中,撑满,左对齐,右对齐)
 Backspace退格
 TabForward,TabBackward(Tab前缩,Tab向后)
 FontSize字体大小:DecreaseFontSize,IncreaseFontSize
 Indentation缩排:DecreaseIndentation, IncreaseIndentation
 Delete删除: Delete选中部分,DeleteNextWord:删除后一字,DeletePreviousWord:删除前一字
 EnterLineBreak:换行
 EnterParagraphBreak:换段
 CorrectSpellingError/IgnoreSpellingError:纠正/忽略拼写错误
 MoveUpByLine,MoveDownByLine: 上/下移一行,
 MoveUpByPage,MoveDownByPage: 上/下移一页
 MoveUpByParagraph,MoveDownByParagraph: 上/下移一段
 MoveLeftByCharacter/MoveRightByCharacter:左/右移一字符
 MoveLeftByWord/MoveRightByWord 左/右移一词
 MoveToDocumentStart/MoveToDocumentEnd:到文章开头/结尾
 MoveToLineStart/MoveToLineEnd:到一行的开头/结尾
 SelectUpByLine,SelectDownByLine:向上/下选一行
 SelectUpByPage,SelectDownByPage:向上/下选一页
 SelectUpByParagraph,SelectDownByParagraph:向上/下选一段
 SelectLeftByCharacter,SelectRightByCharacter:向左/右选中一字
 SelectLeftByWord,SelectRightByWord:向左/右选中一词
 SelectToDocumentStart,SelectToDocumentEnd: 选中到篇头/篇尾
 SelectToLineStart/SelectToLineEnd:选中到行首/行尾
 ToggleBold, ToggleItalic, ToggleUnderline(加粗,斜体,下划线)
 ToggleBullets, ToggleNumbering(列表:加点,加数字)
 ToggleInsert:插入
 ToggleSuperscript,ToggleSubscript(上标字,下标字)

先来举一个简单的例子:

XAML代码:
<StackPanel>
  <Menu>
    <MenuItem Command="ApplicationCommands.Paste" />
  </Menu>
  <TextBox />
</StackPanel>

C#代码:
StackPanel mainStackPanel = new StackPanel();
TextBox pasteTextBox = new TextBox();
Menu stackPanelMenu = new Menu();
MenuItem pasteMenuItem = new MenuItem();

stackPanelMenu.Items.Add(pasteMenuItem);
mainStackPanel.Children.Add(stackPanelMenu);
mainStackPanel.Children.Add(pasteTextBox);

pasteMenuItem.Command = ApplicationCommands.Paste;

上面代码演示了将对文本框设置为焦点时,菜单项可用,点击菜单项时,将执行粘贴命令。


下面列出关于Command的四个概念和四个小问题:
1、WPF中Command(命令)的四个概念:
(1)命令command:要执行的动作。
(2)命令源command source:发出命令的对象(继承自ICommandSource)。
(3)命令目标command target:执行命令的主体
(4)命令绑定command binding:映射命令逻辑的对象
比如在上面示例中,粘贴(Paste)就是命令(command), 菜单项(MenuItem)是命令源(command source), 文本框(TextBox)是命令目标对象(command target), 命令绑定到command binding文本框(TextBox)控件上。

提示:WPF中的命令都继承自ICommand接口。ICommand暴露两个方法:Execute方法、 CanExecute方法和一个事件:CanExecuteChanged。
继承自ICommandSource的有:ButtonBase, MenuItem, Hyperlink和InputBinding。
而Button,GridViewColumnHeader,ToggleButton,RepeatButton继承自ButtonBase。System.Windows.Input.KeyBinding和MouseBinding继承自InputBinding。

2、四个小问题:
(1)如何指定Command Sources?

XAML:(请将“ApplicationCommands.Properties”换成对应的ApplicationCommands属性值,比如:ApplicationCommands.Copy)
<StackPanel>
  <StackPanel.ContextMenu>
    <ContextMenu>
      <MenuItem Command="ApplicationCommands.Properties" />
    </ContextMenu>
  </StackPanel.ContextMenu>
</StackPanel>

同等的C#代码:
StackPanel cmdSourcePanel = new StackPanel();
ContextMenu cmdSourceContextMenu = new ContextMenu();
MenuItem cmdSourceMenuItem = new MenuItem();

cmdSourcePanel.ContextMenu = cmdSourceContextMenu;
cmdSourcePanel.ContextMenu.Items.Add(cmdSourceMenuItem);

cmdSourceMenuItem.Command = ApplicationCommands.Properties;

(2)如何指定快捷键?

XAML代码:
<Window.InputBindings>
  <KeyBinding Key="B"
              Modifiers="Control"

              Command="ApplicationCommands.Open" />
</Window.InputBindings>

C#代码:
KeyGesture OpenKeyGesture = new KeyGesture(
    Key.B,
    ModifierKeys.Control
);

KeyBinding OpenCmdKeybinding = new KeyBinding(ApplicationCommands.Open,OpenKeyGesture);
this.InputBindings.Add(OpenCmdKeybinding);
//也可以这样(下面一句与上面两句的效果等同):
//ApplicationCommands.Open.InputGestures.Add(OpenKeyGesture);
 
(3)如何Command Binding?
XAML代码:
<Window.CommandBindings>
  <CommandBinding Command="ApplicationCommands.Open"
                  Executed="OpenCmdExecuted"
                  CanExecute="OpenCmdCanExecute"/
>
</Window.CommandBindings>

C#代码:
CommandBinding OpenCmdBinding = new CommandBinding(
    ApplicationCommands.Open,
    OpenCmdExecuted,
    OpenCmdCanExecute);

this.CommandBindings.Add(OpenCmdBinding);

具体的事件处理:
C#代码:
void OpenCmdExecuted(object target, ExecutedRoutedEventArgs e)
{
    MessageBox.Show("The command has been invoked.");
}

void OpenCmdCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
    e.CanExecute = true;
}

(4)如何设置Command Target并进行绑定Command Binding?
XAML代码:

<StackPanel>
  <Menu>
    <MenuItem Command="ApplicationCommands.Paste"
              CommandTarget="{Binding ElementName=mainTextBox}" />
  </Menu>
  <TextBox Name="mainTextBox"/>
</StackPanel>
 
C#代码:
StackPanel mainStackPanel = new StackPanel();
TextBox mainTextBox= new TextBox();
Menu stackPanelMenu = new Menu();
MenuItem pasteMenuItem = new MenuItem();

stackPanelMenu.Items.Add(pasteMenuItem);
mainStackPanel.Children.Add(stackPanelMenu);
mainStackPanel.Children.Add(mainTextBox);

pasteMenuItem.Command = ApplicationCommands.Paste;

以上例子全是单条命令绑定的情形,事实上,你也可以多个按钮多条命令绑定到同一控件上,比如:
<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Orientation="Horizontal" Height="25">
<Button Command="Cut" CommandTarget="{Binding ElementName=textBoxInput}" Content="{Binding RelativeSource={RelativeSource Self}, Path=Command.Text}"/>
<Button Command="Copy" CommandTarget="{Binding ElementName=textBoxInput}" Content="{Binding RelativeSource={RelativeSource Self}, Path=Command.Text}"/>
<Button Command="Paste" CommandTarget="{Binding ElementName=textBoxInput}" Content="{Binding RelativeSource={RelativeSource Self}, Path=Command.Text}"/>
<Button Command="Undo" CommandTarget="{Binding ElementName=textBoxInput}" Content="{Binding RelativeSource={RelativeSource Self}, Path=Command.Text}"/>
<Button Command="Redo" CommandTarget="{Binding ElementName=textBoxInput}" Content="{Binding RelativeSource={RelativeSource Self}, Path=Command.Text}"/>
<TextBox x:Name="textBoxInput" Width="200"/>
</StackPanel>

最后,贴出一个完整点的例子:

XAML代码:
<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="WPFCommand.Window1"
    Title="MenuItemCommandTask"
 x:Name="Window"
 Width="500"
 Height="400"
    >
<Window.CommandBindings>
  <CommandBinding Command="ApplicationCommands.Open"
                  Executed="OpenCmdExecuted"
                  CanExecute="OpenCmdCanExecute"/>
<CommandBinding Command="Help" CanExecute="HelpCanExecute" Executed="HelpExecuted" />
</Window.CommandBindings>
<Window.InputBindings>
  <KeyBinding Command="Help" Key="F2" />
  <KeyBinding Command="NotACommand" Key="F1" />
</Window.InputBindings>
    <Canvas>
      <Menu DockPanel.Dock="Top">
        <MenuItem Command="ApplicationCommands.Paste" Width="75" />
      </Menu>
      <TextBox BorderBrush="Black" BorderThickness="2" TextWrapping="Wrap" Text="这个TextBox未成为焦点之前,粘贴菜单不可用。" Width="476" Height="41" Canvas.Left="8" Canvas.Top="25"/>
   <Button Command="ApplicationCommands.Open" Height="32" Width="223" Content="测试弹出对话框" Canvas.Left="8" Canvas.Top="70"/>
    </Canvas>
</Window>

对应的C#代码:
using System;
using System.IO;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Navigation;

namespace WPFCommand
{
 public partial class Window1
 {
  public Window1()
  {
   this.InitializeComponent();
  }
        void OpenCmdExecuted(object target, ExecutedRoutedEventArgs e)
        {
            MessageBox.Show("测试弹出对话框,命令已执行!");
        }

        void OpenCmdCanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = true;
        }

        void HelpCanExecute(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = true;
        }

        void HelpExecuted(object sender, ExecutedRoutedEventArgs e)
        {
            System.Diagnostics.Process.Start("http://www.BrawDraw.com/");
        }
 }
}

你不妨试试在程序执行之后,按下F1或F2试试效果,是不是按F2时浏览器指向"http://www.BrawDraw.com/",而按F1时没有任何效果?这是因为这两句:
  <KeyBinding Command="Help" Key="F2" />
  <KeyBinding Command="NotACommand" Key="F1" />
当按F2时,Help命令执行;当按F1时,由于Command="NotACommand",即窗口忽略此命令的执行。

执行效果图:
Windows Presentation Foundation (WPF)中的命令(Commands)简述

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