我是iOS开发人员,最近我安装了最新的iOS 6进行测试.当我遇到邮件拉动刷新动画时,我决定尝试自己实现它.我试图使用带有UIBezierPath的CAShapeLayer来创建可以向前拖动的相同椭圆形状.并且为了使向下部分向下伸展,我试图使用添加两个控制点的曲线并应用CABasicAnimation.但不幸的是,结果并不像我预期的那样.由于拉伸的线条内部有一点椭圆形.我想椭圆动画必须与其他类做一些事情.如果有人能引导我在这里提出一些想法,我将非常感激.
非常感谢

- (UIBezierPath *)createCircleForRect:(CGRect)bRect
{
    UIBezierPath *circle = [UIBezierPath bezierPath];

    CGFloat rectWidth = bRect.size.width;
    CGFloat rectHeight = bRect.size.height;

    minSize = MIN(rectWidth,rectHeight);

    //center = CGPointMake(minSize/2.0f,minSize/2.0f);

    CGFloat radius = minSize/2.0f - 5.0f;
    startPointOffset = center.x - radius;

    if(startPointOffset == 5.0f)
        testVal = 0;
    else 
        testVal += startPointOffset;

    NSLog(@"startPointOffset =>> %f",startPointOffset);
    NSLog(@"radius =>> %f",radius);

    NSLog(@"after center =>> %f,%f",center.x,center.y);

    [circle addArcWithCenter:center radius:radius startAngle:DEGREES_TO_RADIANS(0) endAngle:DEGREES_TO_RADIANS(180) clockwise:NO];

    [circle moveToPoint:CGPointMake(startPointOffset,center.y)];

    [circle addCurveToPoint:CGPointMake(center.x + radius,center.y) controlPoint1:CGPointMake(center.x - radius,rectHeight + 10.0f) controlPoint2:CGPointMake(center.x + radius,rectHeight + 10.0f)];

    [circle closePath];
    return circle;
}

-(void)startAnimation
{   
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"path"];

    animation.duration = 1.0;

    animation.repeatCount = HUGE_VALF;

    animation.autoreverses = YES;

    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaSEOut];

    animation.fromValue = (id)roundBPath;

    CGRect smallerRect = self.frame;

    smallerRect.size.height += 50;
    smallerRect.size.width -= 80;


    UIBezierPath *newRound = [self createCircleForRect:smallerRect];


    animation.toValue = (id)(newRound.CGPath);


    [shapeLayer addAnimation:animation forKey:@"animatePath"];
}