New UWP Community Toolkit

概述

New UWP Community Toolkit V2.2.0 的版本发布日志中提到了 RadialGauge 的调整，本篇我们结合代码详细讲解 RadialGauge 的实现。

RadialGauge 是一种径向仪表盘控件，使用圆盘面上的指针来显示一定范围的值，这种显示和交互方式，让数据可视化的表现力和吸引力都有很大提高。在实际应用中也有很广泛的使用，如时钟显示，数据展示，仪表盘模拟等等。我们来看一下官方的介绍和官网示例中的展示：

Source: https://github.com/Microsoft/UWPCommunityToolkit/tree/master/Microsoft.Toolkit.Uwp.UI.Controls/RadialGauge

Doc: https://docs.microsoft.com/zh-cn/windows/uwpcommunitytoolkit/controls/radialgauge

Namespace: Microsoft.Toolkit.Uwp.UI.Controls; Nuget: Microsoft.Toolkit.Uwp.UI.Controls;

开发过程

代码分析

先来看看 RadialGauge 的结构组成：

RadialGauge.cs – RadialGauge 的控件定义和事件处理类
RadialGauge.xaml – RadialGauge 的样式文件

1. RadialGauge.xaml

RadialGauge 控件的样式文件，结合上面官方示例的显示图，我们看 Template 部分；主要由以下几个部分组成：

PART_Container – 底层容器，包含了下面三个控件部分
PART_Scale – 比例尺控件
PART_Trail – 仪表盘实际值显示控件
Value and Unit – 实际值文本和单位显示控件

<Style TargetType="local:RadialGauge">
    <Setter Property="UseSystemFocusVisuals" Value="True"></Setter>
    <Setter Property="Foreground" Value="{ThemeResource RadialGaugeForegroundBrush}"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="local:RadialGauge">
                <Viewbox>
                    <Grid x:Name="PART_Container"
                        Width="200"
                        Height="200"
                        Background="Transparent">

                        <!--  Scale  -->
                        <Path Name="PART_Scale"
                            Stroke="{TemplateBinding ScaleBrush}"
                            StrokeThickness="{TemplateBinding ScaleWidth}" />

                        <!--  Trail  -->
                        <Path Name="PART_Trail"
                            Stroke="{TemplateBinding TrailBrush}"
                            StrokeThickness="{TemplateBinding ScaleWidth}" />

                        <!--  Value and Unit  -->
                        <StackPanel HorizontalAlignment="Center"
                                VerticalAlignment="Bottom">
                            <TextBlock Name="PART_ValueText"
                                    Margin="0,0,0,2"
                                    FontSize="20"
                                    FontWeight="SemiBold"
                                    Foreground="{TemplateBinding Foreground}"
                                    Text="{TemplateBinding Value}"
                                    TextAlignment="Center" />
                            <TextBlock Margin="0"
                                    FontSize="16"
                                    Foreground="{ThemeResource RadialGaugeAccentBrush}"
                                    Text="{TemplateBinding Unit}"
                                    TextAlignment="Center" />
                        </StackPanel>
                    </Grid>
                </Viewbox>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

2. RadialGauge.cs

我们先看看 RadialGauge 类的组成：

从上面第一张图中，我们可以看到 RadialGauge 注册了很多依赖属性，不一一列举了，大致分为几个类型：取值和角度属性，显示画刷属性，单位相关属性；属性也对应了修改时的回调事件，下面我们找出几个重点的事件处理方法来讲解：

① OnValueChanged(d)

在数值变化后，触发 OnValueChanged(d) 事件的方法；首先根据设置的取舍值，矫正当前的 Value，计算出对应的角度；给仪表盘的指针赋值，让指针指向当前角度；然后是给显示当前值区间的弧形赋值，如果当前角度值为 360，则整个填充仪表盘，否则根据角度计算出填充的区域，给 ArcSegment，PathFigure，PathGeometry 赋值；最后给仪表盘的数值文本控件赋值；

OnScaleChanged(d) 在刻度修改时触发，本质上讲，数值修改和刻度修改是相通的，所以处理方式也类似，这里不做赘述；

private static void OnValueChanged(DependencyObject d)
{
    RadialGauge radialGauge = (RadialGauge)d;
    if (!double.IsNaN(radialGauge.Value))
    {
        if (radialGauge.StepSize != 0)
        {
            radialGauge.Value = radialGauge.RoundToMultiple(radialGauge.Value, radialGauge.StepSize);
        }

        var middleOfScale = 100 - radialGauge.ScalePadding - (radialGauge.ScaleWidth / 2);
        var valueText = radialGauge.GetTemplateChild(ValueTextPartName) as TextBlock;
        radialGauge.ValueAngle = radialGauge.ValueToAngle(radialGauge.Value);

        // Needle
        if (radialGauge._needle != null)
        {
            radialGauge._needle.RotationAngleInDegrees = (float)radialGauge.ValueAngle;
        }

        // Trail
        var trail = radialGauge.GetTemplateChild(TrailPartName) as Path;
        if (trail != null)
        {
            if (radialGauge.ValueAngle > radialGauge.NormalizedMinAngle)
            {
                trail.Visibility = Visibility.Visible;

                if (radialGauge.ValueAngle - radialGauge.NormalizedMinAngle == 360)
                {
                    // Draw full circle.
                    var eg = new EllipseGeometry();
                    eg.Center = new Point(100, 100);
                    eg.RadiusX = 100 - radialGauge.ScalePadding - (radialGauge.ScaleWidth / 2);
                    eg.RadiusY = eg.RadiusX;
                    trail.Data = eg;
                }
                else
                {
                    // Draw arc.
                    var pg = new PathGeometry();
                    var pf = new PathFigure();
                    pf.IsClosed = false;
                    pf.StartPoint = radialGauge.ScalePoint(radialGauge.NormalizedMinAngle, middleOfScale);
                    var seg = new ArcSegment();
                    seg.SweepDirection = SweepDirection.Clockwise;
                    seg.IsLargeArc = radialGauge.ValueAngle > (180 + radialGauge.NormalizedMinAngle);
                    seg.Size = new Size(middleOfScale, middleOfScale);
                    seg.Point = radialGauge.ScalePoint(Math.Min(radialGauge.ValueAngle, radialGauge.NormalizedMaxAngle), middleOfScale);  // On overflow, stop trail at MaxAngle.
                    pf.Segments.Add(seg);
                    pg.Figures.Add(pf);
                    trail.Data = pg;
                }
            }
            else
            {
                trail.Visibility = Visibility.Collapsed;
            }
        }

        // Value Text
        if (valueText != null)
        {
            valueText.Text = radialGauge.Value.ToString(radialGauge.ValueStringFormat);
        }
    }
}

② OnFaceChanged(d)

任何外观有变化，或刻度值有变化时就会触发，控件整体的 UI 重绘；首先是 Ticks 重绘，然后是 Scale 重绘，后面是 Needle 的重绘，可以看到三种重绘的实现都很类似；最后是执行处理数值变化的方法；

private static void OnFaceChanged(DependencyObject d)
{
    RadialGauge radialGauge = (RadialGauge)d;

    var container = radialGauge.GetTemplateChild(ContainerPartName) as Grid;
    if (container == null || DesignTimeHelpers.IsRunningInLegacyDesignerMode)
    {
        // Bad template.
        return;
    }

    radialGauge._root = container.GetVisual();
    radialGauge._root.Children.RemoveAll();
    radialGauge._compositor = radialGauge._root.Compositor;

    // Ticks.
    SpriteVisual tick;
    for (double i = radialGauge.Minimum; i <= radialGauge.Maximum; i += radialGauge.TickSpacing)
    {
        tick = radialGauge._compositor.CreateSpriteVisual();
        tick.Size = new Vector2((float)radialGauge.TickWidth, (float)radialGauge.TickLength);
        tick.Brush = radialGauge._compositor.CreateColorBrush(radialGauge.TickBrush.Color);
        tick.Offset = new Vector3(100 - ((float)radialGauge.TickWidth / 2), 0.0f, 0);
        tick.CenterPoint = new Vector3((float)radialGauge.TickWidth / 2, 100.0f, 0);
        tick.RotationAngleInDegrees = (float)radialGauge.ValueToAngle(i);
        radialGauge._root.Children.InsertAtTop(tick);
    }

    // Scale Ticks.
    for (double i = radialGauge.Minimum; i <= radialGauge.Maximum; i += radialGauge.TickSpacing)
    {
        tick = radialGauge._compositor.CreateSpriteVisual();
        tick.Size = new Vector2((float)radialGauge.ScaleTickWidth, (float)radialGauge.ScaleWidth);
        tick.Brush = radialGauge._compositor.CreateColorBrush(radialGauge.ScaleTickBrush.Color);
        tick.Offset = new Vector3(100 - ((float)radialGauge.ScaleTickWidth / 2), (float)radialGauge.ScalePadding, 0);
        tick.CenterPoint = new Vector3((float)radialGauge.ScaleTickWidth / 2, 100 - (float)radialGauge.ScalePadding, 0);
        tick.RotationAngleInDegrees = (float)radialGauge.ValueToAngle(i);
        radialGauge._root.Children.InsertAtTop(tick);
    }

    // Needle.
    radialGauge._needle = radialGauge._compositor.CreateSpriteVisual();
    radialGauge._needle.Size = new Vector2((float)radialGauge.NeedleWidth, (float)radialGauge.NeedleLength);
    radialGauge._needle.Brush = radialGauge._compositor.CreateColorBrush(radialGauge.NeedleBrush.Color);
    radialGauge._needle.CenterPoint = new Vector3((float)radialGauge.NeedleWidth / 2, (float)radialGauge.NeedleLength, 0);
    radialGauge._needle.Offset = new Vector3(100 - ((float)radialGauge.NeedleWidth / 2), 100 - (float)radialGauge.NeedleLength, 0);
    radialGauge._root.Children.InsertAtTop(radialGauge._needle);

    OnValueChanged(radialGauge);
}

下面来看一下 RadialGauge 的鼠标点击和触摸手势交互事件处理方法，主要处理逻辑在 SetGaugeValueFromPoint(point) 方法中：

首先计算出当前点击或触摸点相对比仪表盘圆心的坐标，根据坐标计算出角度；再根据最大角度和最小角度的值，计算出可变化的实际区间；最后用当前角度与最小角度的差值，与实际区间做一个比例换算，得到当前角度对应在仪表盘里的数值；

private void SetGaugeValueFromPoint(Point p)
{
    var pt = new Point(p.X - (ActualWidth / 2), -p.Y + (ActualHeight / 2));

    var angle = Math.Atan2(pt.X, pt.Y) / Degrees2Radians;
    var divider = Mod(NormalizedMaxAngle - NormalizedMinAngle, 360);
    if (divider == 0)
    {
        divider = 360;
    }

    var value = Minimum + ((Maximum - Minimum) * Mod(angle - NormalizedMinAngle, 360) / divider);
    if (value < Minimum || value > Maximum)
    {
        // Ignore positions outside the scale angle.
        return;
    }

    Value = value;
}

另外，RadialGauge 控件还支持键盘快捷键操作，当按下 Ctrl 键时，数值变化的幅度是正常变化的 5 倍；而当按下 Left 或 Right 键时，数值会变为最小值或最大值。

调用示例

我们给 RadialGauge 控件设置的范围是 0～180，当前值是 116；最小角度是 210，最大角度是 150；以及每个部分的颜色设置，可以从示例运行图中看出：

<controls:RadialGauge 
        x:Name="RadialGauge"
        Grid.Column="1"
        Value="116"
        Minimum="0"
        Maximum="180"
        StepSize="1"
        IsInteractive="True"
        TickSpacing="18"
        ScaleWidth="8"
        MinAngle="210"
        MaxAngle="150"
        Unit="Units"
        TickBrush="LightGreen"
        ScaleTickBrush="LightBlue"
        ValueBrush="ForestGreen"
        NeedleBrush="ForestGreen"
        NeedleWidth="5" 
        TickLength="18" />

总结

到这里我们就把 UWP Community Toolkit 中的 RadialGauge 控件的源代码实现过程和简单的调用示例讲解完成了，希望能对大家更好的理解和使用这个控件有所帮助。欢迎大家多多交流，谢谢！

最后，再跟大家安利一下 UWPCommunityToolkit 的官方微博：https://weibo.com/u/6506046490, 大家可以通过微博关注最新动态。

衷心感谢 UWPCommunityToolkit 的作者们杰出的工作，Thank you so much, UWPCommunityToolkit authors!!!

本文链接：https://www.cnblogs.com/shaomeng/p/8678684.html

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