使用CABasicAnimation围绕其中心旋转CAShapeLayer弧

Question

我有一个使用CAShapeLayer绘制的圆弧，并且希望它绕圆心旋转。我正在尝试在'transform.rotation'属性上使用CABasicAnimation获得此动画。但是旋转似乎发生在与圆心不同的点上。

-(void)drawRect:(CGRect)rect{
 int radius = 100;
 CAShapeLayer *circle = [CAShapeLayer layer];
 circle.path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 2.0*radius, 2.0*radius) cornerRadius:radius].CGPath;
 circle.fillColor = [UIColor orangeColor].CGColor;
 circle.strokeColor = [UIColor blueColor].CGColor;
 circle.lineWidth = 5;
 circle.strokeStart = 0.0f;
 circle.strokeEnd = 0.1f;
 [self.layer addSublayer:circle];

 CABasicAnimation *spinAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
 spinAnimation.byValue = [NSNumber numberWithFloat:2.0f*M_PI];
 spinAnimation.duration = 4;
 spinAnimation.repeatCount = INFINITY;
 [circle addAnimation:spinAnimation forKey:@"indeterminateAnimation"];
} 

我知道这是一个老问题，但是出路是什么。通过设置图层的边界或锚点，我进行了很多修改，但它尚未绕中心旋转。

circle.bounds = self.frame;

这是将视图添加到视图控制器的方法。

[self.view addSubview:[[ProgressIndicator alloc] initWithFrame:CGRectMake(50, 50, 200, 200)]];

Answer 1

这就是我最终所做的。错误是将动画添加到子层而不是该层。当仅需要绕圆心旋转时，无需在此处修补anchorPoint或位置。

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
       self.backgroundColor = [UIColor clearColor];

       int radius = 50;
       CAShapeLayer *circle = [CAShapeLayer layer];
       circle.path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 2.0*radius, 2.0*radius) cornerRadius:radius].CGPath;
       circle.fillColor = [UIColor clearColor].CGColor;
       circle.strokeColor = [UIColor blueColor].CGColor;
       circle.lineWidth = 5;
       circle.strokeStart = 0.0f;
       circle.strokeEnd = 0.1f;

       [self.layer addSublayer:circle];
    }

   return self; }

- (void)drawRect:(CGRect)rect {

    CABasicAnimation *spinAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
    spinAnimation.byValue = [NSNumber numberWithFloat:2.0f*M_PI];
    spinAnimation.duration = 4;
    spinAnimation.repeatCount = INFINITY;

    [self.layer addAnimation:spinAnimation forKey:@"indeterminateAnimation"]; }