WPF - 绘图与鼠标事件画布 [英] WPF - Drawing on canvas with mouse events

问题描述

我有在画布上处理的鼠标事件的问题。我想用鼠标在上面画，我已经想出这些事件处理程序，但是当我开始画他们没有做任何事情。

I have a problem with handling mouse events on canvas. I want to draw on it using mouse and I've come up with these event handlers, but they don't do anything when I start drawing.

    private void paintSurface_MouseDown(object sender, MouseButtonEventArgs e)
    {
        if (e.ButtonState == MouseButtonState.Pressed)
            currentPoint = e.GetPosition(this);
    }

    private void paintSurface_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.LeftButton == MouseButtonState.Pressed)
        {
            Line line = new Line();

            line.Stroke = SystemColors.WindowFrameBrush;
            line.X1 = currentPoint.X;
            line.Y1 = currentPoint.Y;
            line.X2 = e.GetPosition(this).X;
            line.Y2 = e.GetPosition(this).Y;

            currentPoint = e.GetPosition(this);

            paintSurface.Children.Add(line);
        }
    }

您可以帮我告诉缺少了什么或如何改写它，它就会开始工作？

Can you help me by telling what's missing or how to rewrite it so it'll start working?

推荐答案

我敢打赌，你的画布没有收到鼠标事件，因为它的background属性设置为透明

I'm willing to bet that your canvas isn't receiving mouse events because it's background property is set to transparent

这对我来说工作得很好。

This works fine for me.

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Canvas  Name="paintSurface" MouseDown="Canvas_MouseDown_1" MouseMove="Canvas_MouseMove_1" >
        <Canvas.Background>
            <SolidColorBrush Color="White" Opacity="0"/>
        </Canvas.Background>
    </Canvas>
</Window>


using System;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Input;
using System.Windows.Shapes;

namespace WpfApplication1
{
    public partial class MainWindow : Window
    {

        Point currentPoint = new Point();

        public MainWindow()
        {
            InitializeComponent();
        }

        private void Canvas_MouseDown_1(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            if (e.ButtonState == MouseButtonState.Pressed)
                currentPoint = e.GetPosition(this);
        }

        private void Canvas_MouseMove_1(object sender, System.Windows.Input.MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed)
            {
                Line line = new Line();

                line.Stroke = SystemColors.WindowFrameBrush;
                line.X1 = currentPoint.X;
                line.Y1 = currentPoint.Y;
                line.X2 = e.GetPosition(this).X;
                line.Y2 = e.GetPosition(this).Y;

                currentPoint = e.GetPosition(this);

                paintSurface.Children.Add(line);
            }
        }

    }
}

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