WPF中的鼠标事件详解

Uielement和ContentElement都定义了十个以Mouse开头的事件，8个以PreviewMouse开头的事件，MouseMove,PreviewMouseMove,MouseEnter,Mouseleave的事件处理器类型都是MouseEventHandler类型。这些事件都具备对应得MouseEventargs对象。(没有pre的enter和leave)。

　　当鼠标穿过一个Element时，mousemove会发生很多次，但是mouseenter和mouseleave只会发生一次，分别在鼠标进入element区域以及离开element区域是发生。

　　UIElement和ContentElement定义了两个只读属性，ISmouseOver：如果鼠标在Element上，这个属性为true,如果鼠标不仅在这个Element上，且不在其任何子控件上，那么IsMouseDirectOver也为true。

　　当处理MouseMove ,MouseEnter,Mouseleave事件时我们还可以获取正在按下的鼠标按键式哪一个：Leftbutton,middlebutton,RightButton,以及两个扩充按键XButton1和XButton2。(这五个都是MouseEventargs的属性)，他门的值是MouseButtonState枚举的一个，只有两种状态，Pressed和Released.

　　对于MouseMove事件，你还有可能想要获取当前鼠标的位置，可以使用MouseEventargs的GetPostion方法。通过事件的MouseEventargs的ChangeButton属性可以得知是哪个鼠标按钮被按下。

　　MouseWheel和PreviewWheel事件，主要是处理鼠标滚轮事件，MousewheelEventargs有一个属性Delta属性，它记录鼠标滚轮的刻度，现在的鼠标每滚一下刻度是120，转向用户的时候就是-120.可以利用systemprarameters。IsMouseWheelPresent得知鼠标是否有滚轮。

　　Mouse类的静态方法也可以获取鼠标的位置和状态，也具有静态方法可以添加或删除鼠标事件处理器。MouseDevice类有一些实例方法可以用来获取鼠标位置和按钮状态。

　　鼠标在屏幕上使用一个小小的位图来显示的，此图标称作鼠标光标，在Wpf中，光标就是Cursor类型的对象，可以将Cursor对象设置到FrameworkElement的Cursor属性，就可以将指定的鼠标图标关联到某个element,当然你也可以重载onQueryCursor方法或者给QueryCursor事件添加处理器，鼠标移动就会触发这个事件，QueryCursorEventargs伴随这个事件，他有一个Cursor属性，可以供我们使用。

　　捕获鼠标：在我们鼠标按下后一旦鼠标移出element的区域，就收不到鼠标事件了，但是有时候这个并不是我们想要的结果，所有需要在鼠标进入这个了element的时候获取鼠标，这样鼠标就算离开了这个区域也会获取到鼠标消息。UIelement和contentelement都定义了CaputerMouse方法，Mouse类也提供了Caputer静态方法，让我们可以捕获鼠标，一旦捕获成功就会返回true，在我们的事件处理完成后应该释放这个捕获，使用ReleaseMouseCaputer.

　　如果使用了鼠标捕获，就必须安装LostmouseCaputer事件的处理器，做一些必要的收尾工作。下面我们写一个小程序来使用这些事件：

 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;
 }
 //创建一个Ellipse对象，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);
 //获取鼠标
 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;
 }
 //得到点击的事件 为未来做准备
 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;
 
 }
 //移动椭圆
 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)
 {//如果当前有选定的元素就只将当前元素的大小变化
 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)
 {//如果没有选定的元素就所有的元素一起变化大小
 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;
 }
 }
 }
 }
 }
 
 }