我希望創建一個動畫。我能解釋的最好方法是，如果您可以想象畫一個圓。它從頂部或12點開始，一直沿順時針方向繪制，直到在10秒鐘左右的時間內變成一個完整的圓圈。我來到的壁櫥是使用Core Animation（使用此處的示例代碼）繪制圍繞中心點旋轉的點。但是我對如何畫圈不知所措？任何建議都非常歡迎。非常感謝 ：）
3 回答
縹緲止盈
TA貢獻2041條經驗 獲得超4個贊
這是基于@David的答案的另一種解決方案。這種方法使您可以設置圓形動畫的方向，并提供更多的控制權。編輯：我已經寫了一篇關于如何使用Swift繪制圓的博客文章，我將嘗試與beta保持同步。檢查下面的代碼是否不適合您。
let radius = 100.0
// Create the circle layer
var circle = CAShapeLayer()
// Set the center of the circle to be the center of the view
let center = CGPointMake(CGRectGetMidX(self.frame) - radius, CGRectGetMidY(self.frame) - radius)
let fractionOfCircle = 3.0 / 4.0
let twoPi = 2.0 * Double(M_PI)
// The starting angle is given by the fraction of the circle that the point is at, divided by 2 * Pi and less
// We subtract M_PI_2 to rotate the circle 90 degrees to make it more intuitive (i.e. like a clock face with zero at the top, 1/4 at RHS, 1/2 at bottom, etc.)
let startAngle = Double(fractionOfCircle) / Double(twoPi) - Double(M_PI_2)
let endAngle = 0.0 - Double(M_PI_2)
let clockwise: Bool = true
// `clockwise` tells the circle whether to animate in a clockwise or anti clockwise direction
circle.path = UIBezierPath(arcCenter: center, radius: radius, startAngle: CGFloat(startAngle), endAngle: CGFloat(endAngle), clockwise: clockwise).CGPath
// Configure the circle
circle.fillColor = UIColor.blackColor().CGColor
circle.strokeColor = UIColor.redColor().CGColor
circle.lineWidth = 5
// When it gets to the end of its animation, leave it at 0% stroke filled
circle.strokeEnd = 0.0
// Add the circle to the parent layer
self.layer.addSublayer(circle)
// Configure the animation
var drawAnimation = CABasicAnimation(keyPath: "strokeEnd")
drawAnimation.repeatCount = 1.0
// Animate from the full stroke being drawn to none of the stroke being drawn
drawAnimation.fromValue = NSNumber(double: fractionOfCircle)
drawAnimation.toValue = NSNumber(float: 0.0)
drawAnimation.duration = 30.0
drawAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
// Add the animation to the circle
circle.addAnimation(drawAnimation, forKey: "drawCircleAnimation")
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