objective-c – CABasicAnimation – 设置起始行程位置

发布时间：2020-12-16 07:52:41 所属栏目：百科来源：网络整理

导读：我正在绘制一个基本圆圈的动画.这很好用,除了动画开始在3点位置绘制.有谁知道我怎么能在12点开始？ self.circle = [CAShapeLayer layer];self.circle.fillColor = nil;self.circle.lineWidth = 7;self.circle.strokeColor = [UIColor blackColor].CGColor;se

我正在绘制一个基本圆圈的动画.这很好用,除了动画开始在3点位置绘制.有谁知道我怎么能在12点开始？

self.circle = [CAShapeLayer layer];
self.circle.fillColor = nil;
self.circle.lineWidth = 7;
self.circle.strokeColor = [UIColor blackColor].CGColor;
self.circle.bounds = CGRectMake(0,200,200);
self.circle.path = [UIBezierPath bezierPathWithOvalInRect:self.circle.bounds].CGPath;
[self.view.layer addSublayer:self.circle];

CABasicAnimation *drawAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
drawAnimation.duration            = 5.0;
drawAnimation.repeatCount         = 1.0;
drawAnimation.removedOnCompletion = NO;
drawAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
drawAnimation.toValue   = [NSNumber numberWithFloat:1.0f];
drawAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
[self.circle addAnimation:drawAnimation forKey:@"drawCircleAnimation"];

解决方法

您可以使用bezierPathWithArcCenter而不是bezierPathWithOvalInRect,因为它允许指定开始和结束角度：

CGFloat radius = self.circle.bounds.size.width/2; // Assuming that width == height
self.circle.path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(radius,radius)
                                                  radius:radius
                                              startAngle:(-M_PI/2)
                                                endAngle:(3*M_PI/2)
                                               clockwise:YES].CGPath;

有关角度的含义,请参阅bezierPathWithArcCenter文档.

（编辑：李大同）

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