WPF学习笔记-行为

样式和资源字典能在一定范围上设置界面的属性效果，但是这些都是相对的是静态的，即使是动态的，也是先定义好的，无法直接按人的操作行为去设置效果。

这里来实现拖动功能，需要引用System.Windows.Interactivity.dll程序集

一，创建行为

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Interactivity;
using System.Windows.Media;

namespace CustomsXW
{
    public class DragInCanvasBehavior : Behavior<UIElement>
    {
        private Canvas canvas;

        protected override void OnAttached()
        {
            base.OnAttached();

           //鼠标左键按下，移动，左键松开     事件 
            this.AssociatedObject.MouseLeftButtonDown += AssociatedObject_MouseLeftButtonDown;
            this.AssociatedObject.MouseMove += AssociatedObject_MouseMove;
            this.AssociatedObject.MouseLeftButtonUp += AssociatedObject_MouseLeftButtonUp;
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

       
            this.AssociatedObject.MouseLeftButtonDown -= AssociatedObject_MouseLeftButtonDown;
            this.AssociatedObject.MouseMove -= AssociatedObject_MouseMove;
            this.AssociatedObject.MouseLeftButtonUp -= AssociatedObject_MouseLeftButtonUp;
        }

        // 是否拖动中
        private bool isDragging = false;

        // 鼠标点位置元素
        private Point mouseOffset;

        private void AssociatedObject_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            // 获取画板
            if (canvas == null) canvas = VisualTreeHelper.GetParent(this.AssociatedObject) as Canvas;

            // 开始拖动准备
            isDragging = true;

            //获取当前元素的点位置，默认右上坐标0,0
          
            mouseOffset = e.GetPosition(AssociatedObject);

            // 捕获鼠标
            AssociatedObject.CaptureMouse();
        }

        private void AssociatedObject_MouseMove(object sender, MouseEventArgs e)
        {
            if (isDragging)
            {
                // 拖动中，一直实时获取画板的点位置
                Point point = e.GetPosition(canvas);

                // 实时在画板的上设置元素点位置
                AssociatedObject.SetValue(Canvas.TopProperty, point.Y - mouseOffset.Y);
                AssociatedObject.SetValue(Canvas.LeftProperty, point.X - mouseOffset.X);
            }
        }

        private void AssociatedObject_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if (isDragging)
            {
                //移动结束，松开鼠标，释放捕获鼠标
                AssociatedObject.ReleaseMouseCapture();
                isDragging = false;
            }
        }
    }
}

二，使用行为

记得要引用

<Window x:Class="WPFdemo13.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WPFdemo13"
        mc:Ignorable="d"
        xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
        xmlns:custom="clr-namespace:CustomsXW;assembly=CustomsXW"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Canvas>
            <Rectangle Height="30" Width="30" Stroke="Black" Fill="Red">
                <i:Interaction.Behaviors>
                    <custom:DragInCanvasBehavior></custom:DragInCanvasBehavior>
                    <!--有时候初次加载一直会提示错误，需要重启-->
                </i:Interaction.Behaviors>

            </Rectangle>
            
        </Canvas>

    </Grid>
</Window>

效果：