WPF与缓动(二) 正弦与余弦缓动

本文介绍如何在WPF中实现正弦与余弦缓动效果,通过调整动画的速度变化来达到更加平滑的视觉体验。文章提供了一个具体的缓动动画实现代码示例。

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                                                                           WPF与缓动(二) 正弦与余弦缓动
                                                                                                          周银辉

如果要比二次缓动(请参见WPF与缓动(一) N次缓动)更平缓, 可以使用正弦或余弦缓动.
sin.jpg
如果我们用曲线上点的斜率表示速度,可以发现,由0到PI/2,速度逐渐减小,从PI/2到PI速度逐渐增加.
我们可以总结出如下公式
formula4.PNG
其中位置的改变量相当于Animation中的To与From的差值, t/t(总)相当于animationClock.CurrentProgress.Value, b实际就是From值

参考如下代码:

None.gif using  System;
None.gif
using  System.Collections.Generic;
None.gif
using  System.Text;
None.gif
using  System.Windows.Media.Animation;
None.gif
using  System.Windows;
None.gif
None.gif
namespace  EaseMoveDemo
ExpandedBlockStart.gifContractedBlock.gif
dot.gif {
InBlock.gif    
public class EaseMoveAnimation : DoubleAnimationBase
ExpandedSubBlockStart.gifContractedSubBlock.gif    
dot.gif{
InBlock.gif
InBlock.gif        
public static readonly DependencyProperty FromProperty = DependencyProperty.Register(
InBlock.gif            
"From"typeof(double?), typeof(EaseMoveAnimation), new PropertyMetadata(null));
InBlock.gif
InBlock.gif        
public static readonly DependencyProperty ToProperty = DependencyProperty.Register(
InBlock.gif            
"To"typeof(double?), typeof(EaseMoveAnimation), new PropertyMetadata(null));
InBlock.gif
InBlock.gif        
public double? From
ExpandedSubBlockStart.gifContractedSubBlock.gif        
dot.gif{
InBlock.gif            
get
ExpandedSubBlockStart.gifContractedSubBlock.gif            
dot.gif{
InBlock.gif                
return (double?)this.GetValue(EaseMoveAnimation.FromProperty);
ExpandedSubBlockEnd.gif            }

InBlock.gif            
set
ExpandedSubBlockStart.gifContractedSubBlock.gif            
dot.gif{
InBlock.gif                
this.SetValue(EaseMoveAnimation.FromProperty, value);
ExpandedSubBlockEnd.gif            }

ExpandedSubBlockEnd.gif        }

InBlock.gif
InBlock.gif        
public double? To
ExpandedSubBlockStart.gifContractedSubBlock.gif        
dot.gif{
InBlock.gif            
get
ExpandedSubBlockStart.gifContractedSubBlock.gif            
dot.gif{
InBlock.gif                
return (double?)this.GetValue(EaseMoveAnimation.ToProperty);
ExpandedSubBlockEnd.gif            }

InBlock.gif            
set
ExpandedSubBlockStart.gifContractedSubBlock.gif            
dot.gif{
InBlock.gif                
this.SetValue(EaseMoveAnimation.ToProperty, value);
ExpandedSubBlockEnd.gif            }

ExpandedSubBlockEnd.gif        }

InBlock.gif
InBlock.gif        
//正余弦缓动
InBlock.gif
        protected override double GetCurrentValueCore(double defaultOriginValue, double defaultDestinationValue, AnimationClock animationClock)
ExpandedSubBlockStart.gifContractedSubBlock.gif        
dot.gif{
InBlock.gif            
double from = (this.From==null?defaultDestinationValue:(double)this.From);
InBlock.gif            
double to = (this.To==null?defaultOriginValue:(double)this.To);
InBlock.gif            
double delta = to - from;
InBlock.gif
InBlock.gif            
//加速
InBlock.gif            
//return delta * (1 - Math.Cos(Math.PI / 2 * animationClock.CurrentProgress.Value)) + from;
InBlock.gif
InBlock.gif            
//减速
InBlock.gif            
//return delta * Math.Sin(Math.PI / 2 * animationClock.CurrentProgress.Value) + from;
InBlock.gif
InBlock.gif            
//先加速,后减速
InBlock.gif
            return delta/2 * (1 - Math.Cos(Math.PI * animationClock.CurrentProgress.Value)) + from;
InBlock.gif            
ExpandedSubBlockEnd.gif        }

InBlock.gif
InBlock.gif
InBlock.gif        
protected override System.Windows.Freezable CreateInstanceCore()
ExpandedSubBlockStart.gifContractedSubBlock.gif        
dot.gif{
InBlock.gif            
return new EaseMoveAnimation();
ExpandedSubBlockEnd.gif        }

ExpandedSubBlockEnd.gif    }

ExpandedBlockEnd.gif}

None.gif

源代码下载


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