下面是"WPF+SkiaSharp实现自绘弹幕效果"的完整攻略:
简介
WPF(Windows Presentation Foundation)是一个用于创建Windows桌面应用程序的技术,它提供了大量的视觉效果和控件,使得开发者可以快速地构建出富有表现力的用户界面。SkiaSharp是由Google开发的一个跨平台的2D图形渲染引擎,它可以实现在不同平台上绘制高质量的图形。
在WPF应用程序中,可以通过集成SkiaSharp库来实现自绘弹幕效果。本篇攻略将详细说明如何在WPF应用程序中使用SkiaSharp来绘制弹幕。
步骤
1. 安装SkiaSharp库
首先需要安装NuGet包管理器,并搜索安装SkiaSharp库。
2. 添加引用
在WPF应用程序中,需要在项目中添加对以下两个引用的引用:
using SkiaSharp;
using SkiaSharp.Views.Desktop;
3. 在XAML中添加视图
在XAML中添加一个SKElement
元素,用于绘制弹幕:
<skia:SKElement x:Name="skiaCanvas" PaintSurface="OnPaintSurface"/>
4. 实现绘制方法
在代码中实现绘制方法OnPaintSurface
:
private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
{
var surface = e.Surface;
var canvas = surface.Canvas;
canvas.Clear(SKColors.Transparent);
// 绘制弹幕
foreach (var bullet in Bullets)
{
canvas.DrawText(bullet.Text, bullet.X, bullet.Y, bullet.Paint);
}
}
5. 实现弹幕的更新方法
在代码中实现弹幕的更新方法,例如:
private void UpdateBullets()
{
foreach (var bullet in Bullets)
{
bullet.X += bullet.Speed;
}
// 删除已消失的弹幕
Bullets.RemoveAll(b => b.X > ActualWidth);
}
6. 添加弹幕
在代码中添加弹幕:
var paint = new SKPaint
{
Color = SKColors.White,
TextSize = 24
};
var bullet = new Bullet
{
Text = "Hello, SkiaSharp!",
X = 0,
Y = 100,
Speed = 5,
Paint = paint
};
Bullets.Add(bullet);
其中Bullet
类保存了弹幕的信息,例如文本、坐标、速度和绘制画笔,Bullets
保存所有的弹幕。
7. 更新视图
在代码中使用定时器或者其他方式不断更新弹幕,并刷新视图:
private void OnTimerTick(object sender, EventArgs e)
{
UpdateBullets();
skiaCanvas.InvalidateVisual();
}
示例1
下面是一个最简单的实例,它实现了一个定时添加、滚动的弹幕效果:
public partial class MainWindow : Window
{
private readonly Random _random = new Random();
private readonly List<Bullet> _bullets = new List<Bullet>();
public MainWindow()
{
InitializeComponent();
var timer = new DispatcherTimer();
timer.Interval = TimeSpan.FromMilliseconds(20);
timer.Tick += OnTimerTick;
timer.Start();
}
private void OnTimerTick(object sender, EventArgs e)
{
var paint = new SKPaint
{
Color = SKColors.White,
TextSize = 24
};
var bullet = new Bullet
{
Text = "Hello, SkiaSharp!",
X = 0,
Y = _random.Next(0, (int)ActualHeight),
Speed = 5,
Paint = paint
};
_bullets.Add(bullet);
UpdateBullets();
skiaCanvas.InvalidateVisual();
}
private void UpdateBullets()
{
foreach (var bullet in _bullets)
{
bullet.X += bullet.Speed;
}
_bullets.RemoveAll(b => b.X > ActualWidth);
}
private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
{
var surface = e.Surface;
var canvas = surface.Canvas;
canvas.Clear(SKColors.Transparent);
foreach (var bullet in _bullets)
{
canvas.DrawText(bullet.Text, bullet.X, bullet.Y, bullet.Paint);
}
}
}
public class Bullet
{
public string Text { get; set; }
public float X { get; set; }
public float Y { get; set; }
public float Speed { get; set; }
public SKPaint Paint { get; set; }
}
示例2
下面是一个稍微复杂一点的实例,它使用了MVVM框架的思想,将弹幕的绘制和更新逻辑与UI分离:
ViewModel
public class BulletViewModel : INotifyPropertyChanged
{
private readonly Random _random = new Random();
private SKPaint _paint;
private string _text;
private float _x;
private float _y;
private float _speed;
public SKPaint Paint
{
get => _paint;
set
{
if (_paint != value)
{
_paint = value;
OnPropertyChanged();
}
}
}
public string Text
{
get => _text;
set
{
if (_text != value)
{
_text = value;
OnPropertyChanged();
}
}
}
public float X
{
get => _x;
set
{
if (_x != value)
{
_x = value;
OnPropertyChanged();
}
}
}
public float Y
{
get => _y;
set
{
if (_y != value)
{
_y = value;
OnPropertyChanged();
}
}
}
public float Speed
{
get => _speed;
set
{
if (_speed != value)
{
_speed = value;
OnPropertyChanged();
}
}
}
public BulletViewModel()
{
Paint = new SKPaint
{
Color = SKColors.White,
TextSize = 24
};
Text = "Hello, SkiaSharp!";
X = -Text.Length * Paint.TextSize;
Y = _random.Next(0, 400);
Speed = (float)_random.NextDouble() * 4 + 1;
}
public void Update()
{
X += Speed;
if (X >= 600)
{
X = -Text.Length * Paint.TextSize;
Y = _random.Next(0, 400);
Speed = (float)_random.NextDouble() * 4 + 1;
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
View
<Window x:Class="WpfSkiaSharpDemo.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfSkiaSharpDemo"
xmlns:skia="clr-namespace:SkiaSharp.Views.Desktop;assembly=SkiaSharp.Views.Desktop"
Title="WPF SkiaSharp Demo" Height="450" Width="800">
<Window.DataContext>
<local:MainViewModel/>
</Window.DataContext>
<Grid>
<skia:SKElement x:Name="skiaCanvas" PaintSurface="OnPaintSurface"/>
</Grid>
</Window>
MainViewModel
public class MainViewModel : INotifyPropertyChanged
{
private readonly ObservableCollection<BulletViewModel> _bullets = new ObservableCollection<BulletViewModel>();
public ObservableCollection<BulletViewModel> Bullets
{
get => _bullets;
}
public MainViewModel()
{
var timer = new DispatcherTimer();
timer.Interval = TimeSpan.FromMilliseconds(20);
timer.Tick += OnTimerTick;
timer.Start();
}
private void OnTimerTick(object sender, EventArgs e)
{
foreach (var bullet in Bullets)
{
bullet.Update();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
MainWindow
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
Loaded += OnLoaded;
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
DataContext = new MainViewModel();
for (int i = 0; i < 50; i++)
{
((MainViewModel)DataContext).Bullets.Add(new BulletViewModel());
}
}
private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
{
var surface = e.Surface;
var canvas = surface.Canvas;
canvas.Clear(SKColors.Transparent);
foreach (var bullet in ((MainViewModel)DataContext).Bullets)
{
canvas.DrawText(bullet.Text, bullet.X, bullet.Y, bullet.Paint);
}
}
}
上面这个例子中,ViewModel负责弹幕的更新和保存,View负责弹幕的绘制。这样的架构可以帮助我们实现业务逻辑和UI的分离,使得代码更易于维护和扩展。
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