2012-12-04 15:38 

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float angle = 360 / 6;
for (int i = 0; i < 6; i++) {
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    float offsetAngle = angle * i;
    button.bounds = CGRectMake(0, 0, 32, 32);
    button.center = CGPointMake(cos(offsetAngle * RADIANS) * 160, sin(offsetAngle * RADIANS) * 160);
    button.tag = i;
    CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    CGMutablePathRef path = CGPathCreateMutable();
    pathAnimation.calculationMode = kCAAnimationPaced;
    pathAnimation.fillMode = kCAFillModeForwards;
    pathAnimation.removedOnCompletion = NO;
    pathAnimation.duration = 2;
    CGPathMoveToPoint(path, NULL, button.center.x, button.center.y);
    CGPathAddArc(path, NULL, 0, 0, 160, offsetAngle * M_PI/180, offsetAngle * M_PI/180 + M_PI, YES);
    pathAnimation.path = path;
    CGPathRelease(path);
    [button.layer addAnimation:pathAnimation forKey:@"curve"];
    [tabBarView addSubview:button];
}

因为只是Layer的内容发生的位置变化,其实UIView还是在原来的位置上,如果需要使用应该在Animation结束后重新设定UIView的位置.

 

顺便翻译一下原文:

 

 

CGPathAddArc (

   CGMutablePathRef path,

   const CGAffineTransform *m,

   CGFloat x,

   CGFloat y,

   CGFloat radius,

   CGFloat startAngle,

   CGFloat endAngle,

   bool clockwise

);

path:动画的路径;

m:layer的transform;

x:其实x和y是什么我还没弄明白,根据原文应该是弧的圆心点,但我设置过,这更像是偏移量;

y:同上;

startAngle:起始的角度点,零度是与x轴相交点,度数为顺时针;

endAngle:结束的角度点;

clockwis:是否顺时针.