WPF 动态模拟CPU 使用率曲线图

在工作中经常会遇到需要将一组数据绘制成曲线图的情况，最简单的方法是将数据导入Excel，然后使用绘图功能手动生成曲线图。但是如果基础数据频繁更改，则手动创建图形可能会变得枯燥乏味。本篇将利用DynamicDataDisplay 在WPF 中动态模拟CPU 使用率图表，实现动态生成曲线图。

新建项目将DynamicDataDisplay.dll 加载到References 中，打开MainWindow.xaml 添加命名空间xmlns:d3="http://research.microsoft.com/DynamicDataDisplay/1.0"。通过<d3:ChartPlotter> 创建一个图表框架，在其中添加两条整型坐标轴，X轴：<d3:HorizontalIntegerAxis>，Y轴：<d3:VerticalIntegerAxis>。<d3:Header> 用来设置图表名称，<d3:VerticalAxisTitle> 用来设置Y轴名称。

<Window x:Class="WpfPerformance.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d3="http://research.microsoft.com/DynamicDataDisplay/1.0"
        Title="CPU Performance" Loaded="Window_Loaded" Height="350" Width="525">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="CPU Usage" Margin="20,10,0,0"
                       FontSize="15" FontWeight="Bold"/>
            <TextBlock x:Name="cpuUsageText" Margin="10,10,0,0"
                       FontSize="15"/>
        </StackPanel>
        <d3:ChartPlotter x:Name="plotter" Margin="10,10,20,10" Grid.Row="1">
            <d3:ChartPlotter.VerticalAxis>
                <d3:VerticalIntegerAxis />
            </d3:ChartPlotter.VerticalAxis>

            <d3:ChartPlotter.HorizontalAxis>
                <d3:HorizontalIntegerAxis />
            </d3:ChartPlotter.HorizontalAxis>

            <d3:Header Content="CPU Performance History"/>
            <d3:VerticalAxisTitle Content="Percentage"/>
        </d3:ChartPlotter>
    </Grid>
</Window>

XAML

接下来工作需要通过C#每秒获取一次CPU使用率，并将这些数据生成坐标点（Point）绘制在图表中。以下是MainWindow.xaml.cs 部分的代码内容。

using System;
using System.Diagnostics;
using System.Windows;
using System.Windows.Media;
using System.Windows.Threading;
using Microsoft.Research.DynamicDataDisplay;
using Microsoft.Research.DynamicDataDisplay.DataSources;

namespace WpfPerformance
{
    public partial class MainWindow : Window
    {
        private ObservableDataSource<Point> dataSource = new ObservableDataSource<Point>();
        private PerformanceCounter cpuPerformance = new PerformanceCounter();
        private DispatcherTimer timer = new DispatcherTimer();
        private int i = 0;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void AnimatedPlot(object sender, EventArgs e)
        {
            cpuPerformance.CategoryName = "Processor";
            cpuPerformance.CounterName = "% Processor Time";
            cpuPerformance.InstanceName = "_Total";

            double x = i;
            double y = cpuPerformance.NextValue();

            Point point = new Point(x, y);
            dataSource.AppendAsync(base.Dispatcher, point);

            cpuUsageText.Text = String.Format("{0:0}%", y);
            i++;
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            plotter.AddLineGraph(dataSource, Colors.Green, 2, "Percentage");
            timer.Interval = TimeSpan.FromSeconds(1);
            timer.Tick += new EventHandler(AnimatedPlot);
            timer.IsEnabled = true;
            plotter.Viewport.FitToView();
        }
    }
}

通过ObservableDataSource<Point> 动态存储图表坐标点，PerformanceCounter 获取CPU使用率数值，DispatcherTimer 计时器在规定间隔进行取数操作，整型i 作为CPU使用率坐标点的X轴数值。

private ObservableDataSource<Point> dataSource = new ObservableDataSource<Point>();
private PerformanceCounter cpuPerformance = new PerformanceCounter();
private DispatcherTimer timer = new DispatcherTimer();
private int i = 0;

AnimatedPlot 事件用于构造坐标点，通过设置cpuPerformance 相关参数，并使用NextValue() 方法获取当前CPU使用率数据作为Y值，整型i 作为X值。将X、Y值构造为坐标点（Point），并通过异步方式存储在dataSource 中。

private void AnimatedPlot(object sender, EventArgs e)
{
    cpuPerformance.CategoryName = "Processor";
    cpuPerformance.CounterName = "% Processor Time";
    cpuPerformance.InstanceName = "_Total";

    double x = i;
    double y = cpuPerformance.NextValue();

    Point point = new Point(x, y);
    dataSource.AppendAsync(base.Dispatcher, point);

    cpuUsageText.Text = String.Format("{0:0}%", y);
    i++;
}

最后通过Window_Loaded 将事件加载到<Window> 中，AddLineGraph 方法将dataSource 中的坐标点绘制到图表中，曲线颜色定义为绿色，粗细设置为2，曲线名称为"Percentage"。设置计时器间隔为1秒，连续执行AnimatedPlot 事件实时绘制新坐标点。

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    plotter.AddLineGraph(dataSource, Colors.Green, 2, "Percentage");
    timer.Interval = TimeSpan.FromSeconds(1);
    timer.Tick += new EventHandler(AnimatedPlot);
    timer.IsEnabled = true;
    plotter.Viewport.FitToView();
}