在iOS中围绕枢轴点旋转ImageView [英] Rotate a ImageView around a pivot point in iOS

问题描述

记录和旋转搜索栏

我下面有一个应用程序屏幕，用于录制(最长30秒)音频.

I have an App screen below to record(max 30s) audio.

1. 在录制音频时，如何使小圆圈平滑地旋转为虚线圆上的搜索栏?
2. 当小圆圈沿直线旋转时，如何填充虚线.

谢谢.

推荐答案

答案有两种方法可以使用 PanGesture 和自动使用 Timer .

1.使用UIPanGestureRecognizer:

您可以使用 UIPanGestureRecognizer 实现此目的. circleView 是您的 mainView ，而 nob 是另一个将移出外部的 view 或 imageView circleView

You can achieve this using UIPanGestureRecognizer. circleView is your mainView and nob is another view or imageView which will move outside the circleView

panGesture = UIPanGestureRecognizer(target: self, action: #selector(panHandler(_:)))
nob.addGestureRecognizer(panGesture)

panHandler(_:)

@objc func panHandler(_ gesture: UIPanGestureRecognizer) {
    let point = gesture.location(in: self)
    updateForPoints(point)
}

这是核心逻辑，它将如何工作.

And here is the core logic how will it work.

func updateForPoints(_ point: CGPoint) {

    /*
     * Parametric equation of circle
     * x = a + r cos t
     * y = b + r sin ⁡t
     * a, b are center of circle
     * t (theta) is angle
     * x and y will be points which are on circumference of circle
     *
               270
                |
            _   |   _
                |
     180 -------o------- 360
                |
            +   |   +
                |
               90
     *
     */

    let centerOffset =  CGPoint(x: point.x - circleView.frame.midX, y: point.y - circleView.frame.midY)

    let a: CGFloat = circleView.center.x
    let b: CGFloat = circleView.center.y
    let r: CGFloat = circleView.layer.cornerRadius - 2.5
    let theta: CGFloat = atan2(centerOffset.y, centerOffset.x)
    let newPoints = CGPoint(x: a + r * cos(theta), y: b + r * sin(theta))

    var rect = nob.frame
    rect.origin = newPoints
    nob.center = newPoints
}

2.使用计时器自动移动

let totalSeconds: Int = 30 // You can change it whatever you want
var currentSecond: Int = 1
var timer: Timer?


func degreesToRadians(_ degree: CGFloat) -> CGFloat {
     /// Will convert the degree (180°) to radians (3.14)
     return degree * .pi / 180
}

func angleFromSeconds(_ seconds: Int) -> CGFloat {
     /// Will calculate the angle for given seconds
     let aSliceAngle = 360.0 / CGFloat(totalSeconds)
     let angle = aSliceAngle * CGFloat(seconds) - 90
     return angle
}

/// ------------- TIMER METHODS ------------- ///

func startTimer() {
     stopTimer()
     timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timeDidUpdate(_ :)), userInfo: nil, repeats: true)
     timeDidUpdate(timer!)
}

func stopTimer() {
     currentSecond = 1
     timer?.invalidate()
     timer = nil
}

@objc func timeDidUpdate(_ t: Timer) {
      let angle = angleFromSeconds(currentSecond)
      let theta = degreesToRadians(angle)
      updateAngle(theta: theta, animated: true)
      currentSecond += 1

      if currentSecond > totalSeconds {
         self.stopTimer()
      }
}

/// --------------- MAIN METHOD -------------- ///
func updateAngle(theta: CGFloat, animated: Bool) {

     let a: CGFloat = circleView.center.x
     let b: CGFloat = circleView.center.y
     let r: CGFloat = circleView.layer.cornerRadius
     let newPoints = CGPoint(x: a + r * cos(theta), y: b + r * sin(theta))

     var rect = nob.frame
     rect.origin = newPoints

     if animated {
         UIView.animate(withDuration: 0.1, animations: {
         self.nob.center = newPoints

         /// Uncomment if your nob is not a circle and you want to maintain the angle too
         // self.nob.transform = CGAffineTransform.identity.rotated(by: theta)
         })
     }
     else {
         nob.center = newPoints

         /// Uncomment if your nob is not a circle and you want to maintain the angle too
         //nob.transform = CGAffineTransform.identity.rotated(by: theta)
     }
}

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