一、WPF为何需要命令
我们已经知道WPF里已经有了路由事件,可以发布及传播一些消息,那为什么还需要命令呢?这是因为事件指负责发送消息,对消息如何处理则不管,而命令是有约束力,每个接收者对命令执行统一的行为,比如菜单上的保存,工具栏上的保存都必须是执行同样的保存。
二、命令系统的基本元素
命令(Command):实现了ICommand接口的类,经常使用的有RoutedCommand类
命令源: 是命令的发送者,是实现了ICommandSource接口的类,大部分界面的控件都实现了这个接口,Button, MenuItem 等等。
命令目标:命令的接收者,命令目标是视线了IInputElement接口的类。
命令关联:负责一些逻辑与命令关联起来,比如判断命令是否可以执行,以及执行完毕后做一些处理。
三、四个命令元素之间的关系
四、命令示例
我们让一个按钮发送Hello命令给文本框,文本框接收这个命令后显示“Nice to meet you”.
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< Window x:Class = "DeepXAML.MainWindow" |
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xmlns:local = "clr-namespace:DeepXAML" |
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xmlns:sys = "clr-namespace:System;assembly=mscorlib" |
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Title = "MainWindow" Height = "250" Width = "450" > |
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< StackPanel x:Name = "stackPanel" > |
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< TextBox x:Name = "textBox1" Margin = "10" ></ TextBox > |
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< TextBox x:Name = "textBox2" Margin = "10" ></ TextBox > |
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< Button x:Name = "btnHello" Margin = "10" >Hello</ Button > |
后台代码
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using System.Collections.Generic; |
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using System.Windows.Data; |
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using System.Windows.Documents; |
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using System.Windows.Controls; |
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using System.Windows.Input; |
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public partial class MainWindow : Window |
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private RoutedCommand helloCmd = new RoutedCommand( "Hello" , typeof (MainWindow)); |
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InitializeComponent(); |
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this .btnHello.Command = this .helloCmd; |
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this .helloCmd.InputGestures.Add( new KeyGesture(Key.H, ModifierKeys.Alt)); |
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this .btnHello.CommandTarget = this .textBox1; |
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this .btnHello.CommandTarget = this .textBox2; |
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CommandBinding cb = new CommandBinding(); |
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cb.Command = this .helloCmd; |
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cb.CanExecute += new CanExecuteRoutedEventHandler(cb_CanExecute); |
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cb.Executed += new ExecutedRoutedEventHandler(cb_Executed); |
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this .stackPanel.CommandBindings.Add(cb); |
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void cb_Executed( object sender, ExecutedRoutedEventArgs e) |
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this .textBox1.Text = "Nice to meet you" ; |
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this .textBox2.Text = "Nice to meet you" ; |
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void cb_CanExecute( object sender, CanExecuteRoutedEventArgs e) |
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if (! string .IsNullOrEmpty(textBox1.Text) || ! string .IsNullOrEmpty(textBox2.Text)) |
执行时
一开始按钮状态可用,也就是命令可执行
点击按钮后:
清空一个TextBox,按钮仍然不可执行,因为没达到可执行的条件,两个都清空时,按钮重回可执行状态
五、WPF的命令库
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)
六、命令参数
命令大部分都是类的静态属性,也就是示例只有一个,那么如果两个按钮使用同一个命令如何区分呢?比如新建一个Project,如何区分新建的是Library还是WPF呢?我们可以使用CommandParameter
XAML:
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< Window x:Class = "DeepXAML.MainWindow" |
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xmlns:local = "clr-namespace:DeepXAML" |
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xmlns:sys = "clr-namespace:System;assembly=mscorlib" |
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Title = "MainWindow" Height = "250" Width = "450" > |
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< Window.CommandBindings > |
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< CommandBinding Command = "New" CanExecute = "New_CanExecute" Executed = "New_Executed" ></ CommandBinding > |
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</ Window.CommandBindings > |
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< StackPanel x:Name = "stackPanel" > |
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< TextBox x:Name = "textBox" Margin = "10" ></ TextBox > |
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< Button x:Name = "btnWPF" Margin = "10" Command = "New" CommandParameter = "WPF" >新建WPF</ Button > |
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< Button x:Name = "btnLibrary" Margin = "10" Command = "New" CommandParameter = "Library" >新建Library</ Button > |
后台代码:
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using System.Collections.Generic; |
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using System.Windows.Data; |
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using System.Windows.Documents; |
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using System.Windows.Controls; |
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using System.Windows.Input; |
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public partial class MainWindow : Window |
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InitializeComponent(); |
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private void New_CanExecute( object sender, CanExecuteRoutedEventArgs e) |
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e.CanExecute = string .IsNullOrEmpty(textBox.Text); |
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private void New_Executed( object sender, ExecutedRoutedEventArgs e) |
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if (e.Parameter.ToString() == "Library" ) |
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this .textBox.Text+= "建一个Library" ; |
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if (e.Parameter.ToString() == "WPF" ) |
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this .textBox.Text += "建一个WPF" ; |
运行:
点击第一个按钮
清空文本框再点击第二个按钮