哔哩哔哩(Bilibili)中用户可以通过长按点赞键同时完成点赞、投币、收藏对UP主表示支持，后UP主多用“一键三连”向视频浏览者请求对其作品同时进行点赞、投币、收藏。
“三连按钮”是一组按钮，轻击时当做普通状态按钮使用，当长按 2 秒钟后，转为三连模式，可以控制并显示进度，并在进度完成时弹出一些泡泡
一直想实现这个效果，但由于.NET MAUI对图形填充渲染问题直到.NET 8才修复。想要的效果直到最近才能实现。
两年前Dino老师用UWP实现过“一键三连”:
今天用MAUI实现。
使用.NET MAU实现跨平台支持，本项目可运行于Android、iOS平台。
创建弧形进度条
新建.NET MAUI项目，命名HoldDownButtonGroup
在项目中添加SkiaSharp绘制功能的引用Microsoft.Maui.Graphics.Skia以及SkiaSharp.Views.Maui.Controls。
<ItemGroup>
<PackageReference Include="Microsoft.Maui.Graphics.Skia" Version="7.0.59" />
<PackageReference Include="SkiaSharp.Views.Maui.Controls" Version="2.88.3" />
</ItemGroup>
进度条（ProgressBar）用于展示任务的进度，告知用户当前状态和预期，本项目依赖弧形进度条组件（CircleProgressBar），此组件在本项目中用于展示“三连按钮”长按任务的进度
这里简单介绍弧形进度条组件的原理和实现，更多内容请阅读：[MAUI]弧形进度条与弧形滑块的交互实现。
控件将包含以下可绑定属性：
- Maxiumum：最大值
- Minimum：最小值
- Progress：当前进度
- AnimationLength：动画时长
- BorderWidth：描边宽度
- LabelContent：标签内容
- ContainerColor：容器颜色，即进度条的背景色
- ProgressColor：进度条颜色
创建CircleProgressBar.xaml，代码如下：
<?xml version="1.0" encoding="UTF-8"?>
<ContentView xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:forms="clr-namespace:SkiaSharp.Views.Maui.Controls;assembly=SkiaSharp.Views.Maui.Controls"
x:Class="HoldDownButtonGroup.Controls.CircleProgressBar">
<ContentView.Content>
<Grid>
<forms:SKCanvasView x:Name="canvasView"
PaintSurface="OnCanvasViewPaintSurface" />
<ContentView x:Name="MainContent"></ContentView>
<Label
FontSize="28"
HorizontalOptions="Center"
VerticalOptions="Center"
x:Name="labelView"></Label>
</Grid>
</ContentView.Content>
</ContentView>
SKCanvasView是SkiaSharp.Views.Maui.Controls封装的View控件。
绘制弧
Skia中，通过AddArc方法绘制弧，需要传入一个SKRect对象，其代表一个弧（或椭弧）的外接矩形。startAngle和sweepAngle分别代表顺时针起始角度和扫描角度。
通过startAngle和sweepAngle可以绘制出一个弧，如下图红色部分所示：
在CircleProgressBar.xaml.cs的CodeBehind中，创建OnCanvasViewPaintSurface，通过给定起始角度为正上方，扫描角度为360对于100%进度，通过插值计算出当前进度对应的扫描角度，绘制出进度条。
private void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs args)
{
var SumValue = Maximum - Minimum;
SKImageInfo info = args.Info;
SKSurface surface = args.Surface;
SKCanvas canvas = surface.Canvas;
canvas.Clear();
SKRect rect = new SKRect(_mainRectPadding, _mainRectPadding, info.Width - _mainRectPadding, info.Height - _mainRectPadding);
float startAngle = -90;
float sweepAngle = (float)((_realtimeProgress / SumValue) * 360);
canvas.DrawOval(rect, OutlinePaint);
using (SKPath path = new SKPath())
{
path.AddArc(rect, startAngle, sweepAngle);
canvas.DrawPath(path, ArcPaint);
}
}
其中SumValue表明进度条的总进度，通过Maximum和Minimum计算得出。
public double SumValue => Maximum - Minimum;
创建进度条轨道背景画刷和进度条画刷，其中进度条画刷的StrokeCap属性设置为SKStrokeCap.Round，使得进度条两端为圆形。
protected SKPaint _outlinePaint;
public SKPaint OutlinePaint
{
get
{
if (_outlinePaint == null)
{
RefreshMainRectPadding();
SKPaint outlinePaint = new SKPaint
{
Color = this.ContainerColor.ToSKColor(),
Style = SKPaintStyle.Stroke,
StrokeWidth = (float)BorderWidth,
};
_outlinePaint = outlinePaint;
}
return _outlinePaint;
}
}
protected SKPaint _arcPaint;
public SKPaint ArcPaint
{
get
{
if (_arcPaint == null)
{
RefreshMainRectPadding();
SKPaint arcPaint = new SKPaint
{
Color = this.ProgressColor.ToSKColor(),
Style = SKPaintStyle.Stroke,
StrokeWidth = (float)BorderWidth,
StrokeCap = SKStrokeCap.Round,
};
_arcPaint = arcPaint;
}
return _arcPaint;
}
}
在Progress值变更时，重新渲染进度条，并触发ValueChanged事件。
private void UpdateProgress()
{
this._realtimeProgress = this.Progress;
this.labelView.Text = this.Progress.ToString(LABEL_FORMATE);
this.canvasView?.InvalidateSurface();
}
效果如下
准备物料
点赞、投币、收藏三个按钮的图片来自于哔哩哔哩（Bilibili）网站。这些按钮用svg格式在html中。
我们只需前往哔哩哔哩主站，要打开浏览器的开发者工具，用元素检查器，在找到按钮位置后查看其样式，拷贝path中的svg代码，即可得到这些矢量图片。
拷贝右侧红色区域选中的部分，我们只需要这些svg代码。
在Xaml中我们创建Path元素，并设置Data属性为svg代码。即可得到一个图形
<Path HeightRequest="65"
WidthRequest="65"
x:Name="Icon1"
Fill="Transparent"
Aspect="Uniform"
Data="M 9.77234 30.8573 V 11.7471 H 7.54573 C 5.50932 11.7471 3.85742 13.3931 3.85742 15.425 V 27.1794 C 3.85742 29.2112 5.50932 30.8573 7.54573 30.8573 H 9.77234 Z M 11.9902 30.8573 V 11.7054 C 14.9897 10.627 16.6942 7.8853 17.1055 3.33591 C 17.2666 1.55463 18.9633 0.814421 20.5803 1.59505 C 22.1847 2.36964 23.243 4.32583 23.243 6.93947 C 23.243 8.50265 23.0478 10.1054 22.6582 11.7471 H 29.7324 C 31.7739 11.7471 33.4289 13.402 33.4289 15.4435 C 33.4289 15.7416 33.3928 16.0386 33.3215 16.328 L 30.9883 25.7957 C 30.2558 28.7683 27.5894 30.8573 24.528 30.8573 H 11.9911 H 11.9902 Z"
VerticalOptions="Center"
HorizontalOptions="Center" />
创建气泡
气泡实现分为两个步骤：
Bubble.xaml 创建单一气泡动画
Bubbles.xaml 包含气泡集群。随机生成气泡动画路径，创建气泡集群的动画
Bubbles控件将包含以下可绑定属性：
- Brush：气泡颜色
- BubbleCnt：气泡数量
- BubbleSize：气泡大小
气泡动画算法参考于火火的 BubbleButton，这里只帖关键代码
单一气泡的动画：先变大后消失
public Animation GetAnimation()
{
var scaleAnimation = new Animation();
var scaleUpAnimation0 = new Animation(v => MainBox.Scale = v, 0, 1);
var scaleUpAnimation1 = new Animation(v => MainBox.Scale = v, 1, 0);
scaleAnimation.Add(0, 0.2, scaleUpAnimation0);
scaleAnimation.Add(0.8, 1, scaleUpAnimation1);
scaleAnimation.Finished = () =>
{
this.MainBox.Scale = 0;
};
return scaleAnimation;
}
生成气泡
public void SpawnBubbles()
{
this.PitContentLayout.Clear();
for (int i = 0; i < BubbleCnt; i++)
{
var currentBox = new Bubble();
currentBox.FillColor = i % 2 == 0 ? this.Brush : SolidColorBrush.Transparent;
currentBox.BorderColor = this.Brush;
currentBox.HeightRequest = BubbleSize;
currentBox.WidthRequest = BubbleSize;
currentBox.HorizontalOptions = LayoutOptions.Start;
currentBox.VerticalOptions = LayoutOptions.Start;
this.PitContentLayout.Add(currentBox);
}
}
计算单个气泡的动画路径：随机产生动画运动的随机坐标
private Animation InitAnimation(Bubble element, Size targetSize, bool isOnTop = true)
{
var offsetAnimation = new Animation();
if (targetSize == default)
{
targetSize = element.DesiredSize;
}
var easing = Easing.Linear;
var originX = PitContentLayout.Width / 2;
var originY = PitContentLayout.Height / 2;
var targetX = rnd.Next(-(int)targetSize.Width, (int)targetSize.Width) + (int)targetSize.Width / 2 + originX;
var targetY = isOnTop ? rnd.Next(-(int)(targetSize.Height * 1.5), 0) + (int)targetSize.Height / 2 + originY :
rnd.Next(0, (int)(targetSize.Height * 1.5)) + (int)targetSize.Height / 2 + originY
;
var offsetX = targetX - originX;
var offsetY = targetY - originY;
var offsetAnimation1 = new Animation(v => element.TranslationX = v, originX - targetSize.Width / 2, targetX - targetSize.Width / 2, easing);
var offsetAnimation2 = new Animation(v => element.TranslationY = v, originY - targetSize.Height / 2, targetY - targetSize.Height / 2, easing);
offsetAnimation.Add(0.2, 0.8, offsetAnimation1);
offsetAnimation.Add(0.2, 0.8, offsetAnimation2);
offsetAnimation.Add(0, 1, element.BoxAnimation);
offsetAnimation.Finished = () =>
{
element.TranslationX = originX;
element.TranslationY = originY;
element.Rotation = 0;
};
return offsetAnimation;
}
开始气泡动画
public void StartAnimation()
{
Content.AbortAnimation("ReshapeAnimations");
var offsetAnimationGroup = new Animation();
foreach (var item in this.PitContentLayout.Children)
{
if (item is Bubble)
{
var isOntop = this.PitContentLayout.Children.IndexOf(item) > this.PitContentLayout.Children.Count / 2;
var currentAnimation = InitAnimation(item as Bubble, targetSize, isOntop);
offsetAnimationGroup.Add(0, 1, currentAnimation);
}
}
offsetAnimationGroup.Commit(this, "ReshapeAnimations", 16, 400);
}
创建手势
可喜可贺，在新发布的.NET 8 中， .NET MAUI 引入了指针手势识别器(PointerGestureRecognizer)，使用方式如下，终于不用自己实现手势监听控件了。
Xaml:
<Image Source="dotnet_bot.png">
<Image.GestureRecognizers>
<PointerGestureRecognizer PointerEntered="OnPointerEntered"
PointerExited="OnPointerExited"
PointerMoved="OnPointerMoved" />
</Image.GestureRecognizers>
</Image>
C#:
void OnPointerEntered(object sender, PointerEventArgs e)
{
// Handle the pointer entered event
}
void OnPointerExited(object sender, PointerEventArgs e)
{
// Handle the pointer exited event
}
void OnPointerMoved(object sender, PointerEventArgs e)
{
// Handle the pointer moved event
}
具体请阅读官方文档：
.NET 8 中 .NET MAUI 的新增功能以及
识别指针手势
在本项目中，需要监听长按动作，当“三连按钮”长按2秒后，转为三连模式，此时需要监听手指释放情况，当时长不足时取消三连。
由于在之前的文章中实现过监听手势，这里仅简单介绍定义，其余内容不再重复，如需了解请阅读： [MAUI程序设计] 用Handler实现自定义跨平台控件
定义可以监听的手势类别，分别是按下、移动、抬起、取消、进入、退出
public enum TouchActionType
{
Entered,
Pressed,
Moved,
Released,
Exited,
Cancelled
}
添加手势监听器TouchRecognizer，它将提供一个事件OnTouchActionInvoked，用触发手势动作。
public partial class TouchRecognizer: IDisposable
{
public event EventHandler<TouchActionEventArgs> OnTouchActionInvoked;
public partial void Dispose();
}
EventArg类TouchActionEventArgs，用于传递手势动作的参数
创建交互与动效
在页面创建完三个按钮后，在CodeBehind中编写交互逻辑
添加更新圆环进度的方法UpdateProgressWithAnimate，此方法根据圆环进度的百分比，计算圆环进度的动画时间，并开始动画
private void UpdateProgressWithAnimate(CircleProgressBar progressElement, double progressTarget = 100, double totalLenght = 5*1000, Action<double, bool> finished = null)
{
Content.AbortAnimation("ReshapeAnimations");
var scaleAnimation = new Animation();
double progressOrigin = progressElement.Progress;
var animateAction = (double r) =>
{
progressElement.Progress = r;
};
var scaleUpAnimation0 = new Animation(animateAction, progressOrigin, progressTarget);
scaleAnimation.Add(0, 1, scaleUpAnimation0);
var calcLenght = (double)(Math.Abs((progressOrigin - progressTarget) / 100)) * totalLenght;
scaleAnimation.Commit(progressElement, "ReshapeAnimations", 16, (uint)calcLenght, finished: finished);
}
创建“三连成功”的动画方法StartCelebrationAnimate，在这里通过改变按钮的Scale和Fill属性，实现三连成功时“点亮”图标的动画效果。
private void StartCelebrationAnimate(Path progressElement, Action<double, bool> finished = null)
{
var toColor = (Color)this.Resources["BrandColor"];
var fromColor = (Color)this.Resources["DisabledColor"];
var scaleAnimation = new Animation();
var scaleUpAnimation0 = new Animation(v => progressElement.Scale=v, 0, 1.5);
var scaleUpAnimation1 = new Animation(v => progressElement.Fill=GetColor(v, fromColor, toColor), 0, 1);
var scaleUpAnimation2 = new Animation(v => progressElement.Scale=v, 1.5, 1);
scaleAnimation.Add(0, 0.5, scaleUpAnimation0);
scaleAnimation.Add(0, 1, scaleUpAnimation1);
scaleAnimation.Add(0.5, 1, scaleUpAnimation2);
scaleAnimation.Commit(progressElement, "CelebrationAnimate", 16, 400, finished: finished);
}
按钮触发TouchContentView_OnTouchActionInvoked事件：
_dispatcherTimer作用是延时1秒，如果按钮被点击，则开始执行后续操作。当按钮被点击时此Timer会开。
一秒后，开始进入“三连模式”，此时更新圆环进度，当进度完成后开始气泡动画和“三连成功”的动画。
若中途按钮被释放，则取消此Timer，并重置圆环进度。
若按钮未进入“三连模式”，则直接播放按钮的点击动画。
private void TouchContentView_OnTouchActionInvoked(object sender, TouchActionEventArgs e)
{
var layout = ((Microsoft.Maui.Controls.Layout)(sender as TouchContentView).Content).Children;
var bubbles = layout[0] as Bubbles;
var circleProgressBar = layout[1] as CircleProgressBar;
switch (e.Type)
{
case TouchActionType.Entered:
break;
case TouchActionType.Pressed:
_dispatcherTimer =Dispatcher.CreateTimer();
_dispatcherTimer.Interval=new TimeSpan(0, 0, 1);
_dispatcherTimer.Tick+= async (o, e) =>
{
_isInProgress=true;
this.UpdateProgressWithAnimate(ProgressBar1, 100, 2*1000, (d, b) =>
{
if (circleProgressBar.Progress==100)
{
this.bubbles1.StartAnimation();
StartCelebrationAnimate(this.Icon1);
}
});
this.UpdateProgressWithAnimate(ProgressBar2, 100, 2*1000, (d, b) =>
{
if (circleProgressBar.Progress==100)
{
this.bubbles2.StartAnimation();
StartCelebrationAnimate(this.Icon2);
}
});
this.UpdateProgressWithAnimate(ProgressBar3, 100, 2*1000, (d, b) =>
{
if (circleProgressBar.Progress==100)
{
this.bubbles3.StartAnimation();
StartCelebrationAnimate(this.Icon3);
}
});
};
_dispatcherTimer.Start();
break;
case TouchActionType.Moved:
break;
case TouchActionType.Released:
if (!_isInProgress)
{
var brandColor = (Color)this.Resources["BrandColor"];
var disabledColor = (Color)this.Resources["DisabledColor"];
if (circleProgressBar.Progress==100)
{
this.UpdateProgressWithAnimate(ProgressBar1, 0, 1000);
this.UpdateProgressWithAnimate(ProgressBar2, 0, 1000);
this.UpdateProgressWithAnimate(ProgressBar3, 0, 1000);
(ProgressBar1.LabelContent as Path).Fill=disabledColor;
(ProgressBar2.LabelContent as Path).Fill=disabledColor;
(ProgressBar3.LabelContent as Path).Fill=disabledColor;
}
else
{
if (((circleProgressBar.LabelContent as Path).Fill as SolidColorBrush).Color==disabledColor)
{
StartCelebrationAnimate(circleProgressBar.LabelContent as Path);
}
else
{
(circleProgressBar.LabelContent as Path).Fill=disabledColor;
}
}
}
if (_dispatcherTimer!=null)
{
if (_dispatcherTimer.IsRunning)
{
_dispatcherTimer.Stop();
_isInProgress=false;
}
_dispatcherTimer=null;
if (circleProgressBar.Progress==100)
{
return;
}
this.UpdateProgressWithAnimate(ProgressBar1, 0, 1000);
this.UpdateProgressWithAnimate(ProgressBar2, 0, 1000);
this.UpdateProgressWithAnimate(ProgressBar3, 0, 1000);
}
break;
case TouchActionType.Exited:
break;
case TouchActionType.Cancelled:
break;
default:
break;
}
}
进入三联模式动画效果如下：
未进入三联模式动画效果如下：
最终效果如下：
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