如何在ios中制作圆形动画

Question

如果单击“锻炼”按钮，我想显示红色圆形动画并围绕图像。我想在Storyboard中移动另一个班级。我怎么能做到这一点？

Answer 1

使用UIBezierPath或CAShapeLayer，即可实现此目标。我在我的一个项目中测试了以下代码并发现它正常工作：

- (void)viewDidLoad
{
    [super viewDidLoad];

    int radius = 50;
    CAShapeLayer *circle = [CAShapeLayer layer];
    // Make a circular shape
    circle.path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 2.0*radius, 2.0*radius)
                                             cornerRadius:radius].CGPath;
    // Center the shape in self.view
    circle.position = CGPointMake(CGRectGetMidX(self.view.frame)-radius,
                                  CGRectGetMidY(self.view.frame)-radius);

    // Configure the apperence of the circle
    circle.fillColor = [UIColor clearColor].CGColor;
    circle.strokeColor = [UIColor redColor].CGColor;
    circle.lineWidth = 5;

    // Add to parent layer
    [self.view.layer addSublayer:circle];

    // Configure animation
    CABasicAnimation *drawAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    drawAnimation.duration            = 5.0;
    drawAnimation.repeatCount         = 1.0;  // Animate only once..

    // Animate from no part of the stroke being drawn to the entire stroke being drawn
    drawAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
    drawAnimation.toValue   = [NSNumber numberWithFloat:1.0f];

    // Experiment with timing to get the appearence to look the way you want
    drawAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];

    // Add the animation to the circle
    [circle addAnimation:drawAnimation forKey:@"draw"];
    // Do any additional setup after loading the view, typically from a nib.
}

输出如下：