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 override void 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 override void 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 override void 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 override void 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 override void 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 override void 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 override void OnLostMouseCapture(MouseEventArgs e)
        {
            base.OnLostMouseCapture(e);
            if (IsDrawing)
            {
                canvas.Children.Remove(elips);
                IsDrawing = false;
            }
        }

        protected override void 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;
                    }
                }
            }
        }
    }

}