[源码下载]

背水一战 Windows 10 (60) - 控件（媒体类）: Pointer 涂鸦板, InkCanvas 涂鸦板

作者：webabcd


介绍
背水一战 Windows 10 之 控件（媒体类）

• 通过处理 Pointer 相关事件实现一个简单的涂鸦板
• InkCanvas 基础知识

示例
1、演示如何通过 Pointer 相关事件的处理，来实现一个简单的涂鸦板
Controls/MediaControl/InkSimple.xaml

<Page
    x:Class="Windows10.Controls.MediaControl.InkSimple"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Windows10.Controls.MediaControl"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">
    
    <Grid Background="Transparent">
        <StackPanel Margin="10 0 10 10">

            <Button Name="btnClear" Content="清除" Click="btnClear_Click" Margin="5" />

            <Canvas Name="canvas" Background="Blue" Width="800" Height="480" HorizontalAlignment="Left" Margin="5" />

        </StackPanel>
    </Grid>
</Page>

Controls/MediaControl/InkSimple.xaml.cs

/*
 * 本例用于演示如何通过 Pointer 相关事件的处理，来实现一个简单的涂鸦板
 */

using System;
using System.Collections.Generic;
using Windows.Foundation;
using Windows.UI;
using Windows.UI.Input;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Shapes;

namespace Windows10.Controls.MediaControl
{
    public sealed partial class InkSimple : Page
    {
        // 用于保存触摸点（PointerId - Point）
        private Dictionary<uint, Point?> _dicPoint;

        public InkSimple()
        {
            this.InitializeComponent();

            canvas.PointerPressed += canvas_PointerPressed;
            canvas.PointerMoved += canvas_PointerMoved;
            canvas.PointerReleased += canvas_PointerReleased;
            canvas.PointerExited += canvas_PointerExited;

            _dicPoint = new Dictionary<uint, Point?>();
        }

        void canvas_PointerPressed(object sender, PointerRoutedEventArgs e)
        {
            // 指针按下后，保存此触摸点
            PointerPoint pointerPoint = e.GetCurrentPoint(canvas);
            _dicPoint[pointerPoint.PointerId] = pointerPoint.Position;
        }

        void canvas_PointerMoved(object sender, PointerRoutedEventArgs e)
        {
            PointerPoint pointerPoint = e.GetCurrentPoint(canvas);

            if (_dicPoint.ContainsKey(pointerPoint.PointerId) && _dicPoint[pointerPoint.PointerId].HasValue)
            {
                Point currentPoint = pointerPoint.Position;
                Point previousPoint = _dicPoint[pointerPoint.PointerId].Value;

                // 如果指针移动过程中，两个点间的距离超过 4 则在两点间绘制一条直线，以完成涂鸦
                if (ComputeDistance(currentPoint, previousPoint) > 4)
                {
                    Line line = new Line()
                    {
                        X1 = previousPoint.X,
                        Y1 = previousPoint.Y,
                        X2 = currentPoint.X,
                        Y2 = currentPoint.Y,
                        StrokeThickness = 5,
                        Stroke = new SolidColorBrush(Colors.Orange),
                        StrokeEndLineCap = PenLineCap.Round
                    };

                    _dicPoint[pointerPoint.PointerId] = currentPoint;
                    canvas.Children.Add(line);
                }
            }
        }

        void canvas_PointerReleased(object sender, PointerRoutedEventArgs e)
        {
            // 指针释放后，从字典中删除此 PointerId 的数据
            PointerPoint pointerPoint = e.GetCurrentPoint(canvas);
            if (_