WPF中的鼠標事件詳解

Uielement和ContentElement都定義了十個以Mouse開頭的事件，8個以PreviewMouse開頭的事件，MouseMove,PreviewMouseMove,MouseEnter,Mouseleave的事件處理器類型都是MouseEventHandler類型。這些事件都具備對應得MouseEventargs對象。(沒有pre的enter和leave)。

　　當鼠標穿過一個Element時，mousemove會發生很多次，但是mouseenter和mouseleave只會發生一次，分別在鼠標進入element區域以及離開element區域是發生。

　　UIElement和ContentElement定義了兩個只讀屬性，ISmouseOver：如果鼠標在Element上，這個屬性為true,如果鼠標不僅在這個Element上，且不在其任何子控件上，那么IsMouseDirectOver也為true。

　　當處理MouseMove ,MouseEnter,Mouseleave事件時我們還可以獲取正在按下的鼠標按鍵式哪一個：Leftbutton,middlebutton,RightButton,以及兩個擴充按鍵XButton1和XButton2。(這五個都是MouseEventargs的屬性)，他門的值是MouseButtonState枚舉的一個，只有兩種狀態，Pressed和Released.

　　對于MouseMove事件，你還有可能想要獲取當前鼠標的位置，可以使用MouseEventargs的GetPostion方法。通過事件的MouseEventargs的ChangeButton屬性可以得知是哪個鼠標按鈕被按下。

　　MouseWheel和PreviewWheel事件，主要是處理鼠標滾輪事件，MousewheelEventargs有一個屬性Delta屬性，它記錄鼠標滾輪的刻度，現在的鼠標每滾一下刻度是120，轉向用戶的時候就是-120.可以利用systemprarameters。IsMouseWheelPresent得知鼠標是否有滾輪。

　　Mouse類的靜態方法也可以獲取鼠標的位置和狀態，也具有靜態方法可以添加或刪除鼠標事件處理器。MouseDevice類有一些實例方法可以用來獲取鼠標位置和按鈕狀態。

　　鼠標在屏幕上使用一個小小的位圖來顯示的，此圖標稱作鼠標光標，在Wpf中，光標就是Cursor類型的對象，可以將Cursor對象設置到FrameworkElement的Cursor屬性，就可以將指定的鼠標圖標關聯到某個element,當然你也可以重載onQueryCursor方法或者給QueryCursor事件添加處理器，鼠標移動就會觸發這個事件，QueryCursorEventargs伴隨這個事件，他有一個Cursor屬性，可以供我們使用。

　　捕獲鼠標：在我們鼠標按下后一旦鼠標移出element的區域，就收不到鼠標事件了，但是有時候這個并不是我們想要的結果，所有需要在鼠標進入這個了element的時候獲取鼠標，這樣鼠標就算離開了這個區域也會獲取到鼠標消息。UIelement和contentelement都定義了CaputerMouse方法，Mouse類也提供了Caputer靜態方法，讓我們可以捕獲鼠標，一旦捕獲成功就會返回true，在我們的事件處理完成后應該釋放這個捕獲，使用ReleaseMouseCaputer.

　　如果使用了鼠標捕獲，就必須安裝LostmouseCaputer事件的處理器，做一些必要的收尾工作。下面我們寫一個小程序來使用這些事件：

 using System;
 using System.Windows;
 using System.Windows.Input;
 using System.Windows.Controls;
 using System.Windows.Shapes;
 using System.Windows.Media;
 
 
 namespace WPFDemo
 {
 class DrawCircles : Window
 {
 Canvas canvas;
 Boolean IsDrawing;
 Ellipse elips;
 Point ptcenter;
 Boolean IsDragging;
 Boolean IsChanging;
 FrameworkElement elDragging;
 Ellipse ChangeElips;
 Point ptmousestart, ptElementStart;
 
 [STAThread]
 static void Main()
 {
 Application app = new Application();
 app.Run(new DrawCircles());
 }
 
 public DrawCircles()
 {
 Title = "Draw Circles";
 Content = canvas = new Canvas();
 Line line = new Line();
 line.Width = 1;
 line.X1 = 0;
 line.X2 = canvas.ActualWidth/2;
 line.Y1 = canvas.ActualHeight / 2;
 line.Y2 = 0;
 canvas.Children.Add(line);
 line.Stroke = SystemColors.WindowTextBrush;
 }
 protected overridevoid OnMouseLeftButtonDown(MouseButtonEventArgs e)
 {
 base.OnMouseLeftButtonDown(e);
 if (IsDragging)
 {
 return;
 }
 //創建一個Ellipse對象，并且把它加入到Canvas中
 ptcenter = e.GetPosition(canvas);
 elips = new Ellipse();
 elips.Stroke = SystemColors.WindowTextBrush;
 //elips.StrokeThickness = 0.1;
 elips.Width = 0;
 elips.Height = 0;
 elips.MouseEnter += new MouseEventHandler(elips_MouseEnter);
 elips.MouseLeave += new MouseEventHandler(elips_MouseLeave);
 canvas.Children.Add(elips);
 Canvas.SetLeft(elips, ptcenter.X);
 Canvas.SetTop(elips, ptcenter.Y);
 //獲取鼠標
 CaptureMouse();
 IsDrawing = true;
 
 }
 
 void elips_MouseLeave(object sender, MouseEventArgs e)
 {
 ChangeElips = sender as Ellipse;
 ChangeElips.Stroke = SystemColors.WindowTextBrush;
 ChangeElips = null;
 if ( IsChanging)
 {
 IsChanging = false;
 }
 //throw new NotImplementedException();
 }
 
 void elips_MouseEnter(object sender, MouseEventArgs e)
 {
 ChangeElips = sender as Ellipse;
 ChangeElips.Stroke = SystemColors.WindowFrameBrush;
 IsChanging = true;
 //throw new NotImplementedException();
 }
 protected overridevoid OnMouseRightButtonDown(MouseButtonEventArgs e)
 {
 base.OnMouseRightButtonDown(e);
 if (IsDrawing)
 {
 return;
 }
 //得到點擊的事件 為未來做準備
 ptmousestart = e.GetPosition(canvas);
 elDragging = canvas.InputHitTest(ptmousestart) as FrameworkElement;
 if (elDragging != null)
 {
 ptElementStart = new Point(Canvas.GetLeft(elDragging),
 Canvas.GetTop(elDragging));
 IsDragging = true;
 }
 
 }
 
 protected overridevoid OnMouseDown(MouseButtonEventArgs e)
 {
 base.OnMouseDown(e);
 if (e.ChangedButton == MouseButton.Middle)
 {
 Shape shape = canvas.InputHitTest(e.GetPosition(canvas))  as Shape;
 if (shape != null)
 {
 shape.Fill = (shape.Fill == Brushes.Red ?
 Brushes.Transparent : Brushes.Red);
 
 }
 }
 }
 
 protected overridevoid OnMouseMove(MouseEventArgs e)
 {
 base.OnMouseMove(e);
 Point ptmouse = e.GetPosition(canvas);
 
 if (IsDrawing)
 {
 double draddius = Math.Sqrt(Math.Pow(ptcenter.X - ptmouse.X, 2) +
 Math.Pow(ptcenter.Y - ptmouse.Y, 2));
 Canvas.SetLeft(elips, ptcenter.X - draddius);
 Canvas.SetTop(elips, ptcenter.Y - draddius);
 elips.Width = 2 * draddius;
 elips.Height = 2 * draddius;
 
 }
 //移動橢圓
 else if (IsDragging)
 {
 Canvas.SetLeft(elDragging, ptElementStart.X + ptmouse.X - ptmousestart.X);
 Canvas.SetTop(elDragging, ptElementStart.Y + ptmouse.Y - ptmousestart.Y);
 }
 }
 
 protected overridevoid OnMouseUp(MouseButtonEventArgs e)
 {
 base.OnMouseUp(e);
 if (IsDrawing&&e.ChangedButton == MouseButton.Left)
 {
 elips.Stroke = Brushes.Blue;
 elips.StrokeThickness =elips.Width/8;
 elips.Fill = Brushes.Red;
 IsDrawing = false;
 ReleaseMouseCapture();
 }
 else if (IsDragging&&e.ChangedButton == MouseButton.Right)
 {
 IsDragging = false;
 }
 }
 protected overridevoid OnTextInput(TextCompositionEventArgs e)
 {
 base.OnTextInput(e);
 if (e.Text.IndexOf('\x18')!=-1)
 {
 if (IsDrawing)
 {
 ReleaseMouseCapture();
 }
 else if (IsDragging)
 {
 Canvas.SetLeft(elDragging, ptElementStart.X);
 Canvas.SetTop(elDragging, ptElementStart.Y);
 IsDragging = false;
 }
 }
 }
 protected overridevoid OnLostMouseCapture(MouseEventArgs e)
 {
 base.OnLostMouseCapture(e);
 if (IsDrawing)
 {
 canvas.Children.Remove(elips);
 IsDrawing = false;
 }
 }
 
 protected overridevoid OnMouseWheel(MouseWheelEventArgs e)
 {
 base.OnMouseWheel(e);
 if (IsChanging &&ChangeElips!=null)
 {//如果當前有選定的元素就只將當前元素的大小變化
 Point pt = new Point(Canvas.GetLeft(ChangeElips) + ChangeElips.Width / 2, Canvas.GetTop(ChangeElips) + ChangeElips.Height / 2);
 double draddius = (e.Delta*1.0 / 1200 + 1) * ChangeElips.Height;
 
 Canvas.SetLeft(ChangeElips, pt.X - draddius/2);
 Canvas.SetTop(ChangeElips, pt.Y - draddius/2);
 ChangeElips.Height = draddius;
 ChangeElips.Width = draddius;
 }
 else if (ChangeElips==null)
 {//如果沒有選定的元素就所有的元素一起變化大小
 double canvax = canvas.ActualWidth;
 double canvay = canvas.ActualHeight;
 foreach (UIElement elisp  in canvas.Children)
 {
 Ellipse els = elisp as Ellipse;
 if (els!=null)
 {
 double draddius = (e.Delta * 1.0 / 1200 + 1) * els.Height;
 double x1 = Canvas.GetLeft(els);
 double y1 = Canvas.GetTop(els);
 double draddiusx = (e.Delta * 1.0 / 1200) * (x1 - canvax / 2) + x1;
 double draddiusY = (e.Delta * 1.0 / 1200) * (y1 - canvay / 2) + y1;
 Canvas.SetLeft(els,draddiusx);
 Canvas.SetTop(els,draddiusY);
 els.Height = draddius;
 els.Width = draddius;
 els.StrokeThickness = els.Width /8;
 }
 }
 }
 }
 }
 
 }