后退按钮启动 UIViewPropertyAnimator？答案

【问题标题】：Back button starts a UIViewPropertyAnimator?后退按钮启动 UIViewPropertyAnimator？
【发布时间】：2018-06-13 20:00:30
【问题描述】：

我有一个带有摄像头的 ViewController 用于录制视频。顶部有一个旋转的圆圈，表示正在录制视频。这是这样设置的：

class CameraViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    private var animator: UIViewPropertyAnimator?

    @objc func handleTap(_ gesture:UITapGestureRecognizer) {
        if animator == nil {
            createAnimation()
        }
        startRecording()
    }
    private func createAnimation() {
        animator = UIViewPropertyAnimator.runningPropertyAnimator(withDuration: 4, delay: 0, options: [.curveLinear,.allowUserInteraction], animations: {
            UIView.animateKeyframes(withDuration: 4, delay: 0, animations: {
                UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 1.0 / 3.0) {
                    self.recordingSpinner.transform = .init(rotationAngle: .pi * 2 * 1 / 3)
                }
                UIView.addKeyframe(withRelativeStartTime: 1.0 / 3.0, relativeDuration: 1.0 / 3.0) {
                    self.recordingSpinner.transform = .init(rotationAngle: .pi * 2 * 2 / 3)
                }
                UIView.addKeyframe(withRelativeStartTime: 2.0 / 3.0, relativeDuration: 1.0 / 3.0) {
                    self.recordingSpinner.transform = .identity
                }
            })
        }, completion: { [weak self] _ in
            self?.createAnimation()
        })
    }

    func startRecording() {

        if movieOutput.isRecording == false {

            animator?.startAnimation()
            let connection = movieOutput.connection(with: AVMediaType.video)
            if (connection?.isVideoOrientationSupported)! {
                connection?.videoOrientation = currentVideoOrientation()
            }

            if (connection?.isVideoStabilizationSupported)! {
                connection?.preferredVideoStabilizationMode = AVCaptureVideoStabilizationMode.auto
            }

            let device = activeInput.device
            if (device.isSmoothAutoFocusSupported) {
                do {
                    try device.lockForConfiguration()
                    device.isSmoothAutoFocusEnabled = false
                    device.unlockForConfiguration()
                } catch {
                    print("Error setting configuration: \(error)")
                }

            }

            let outputFileName = NSUUID().uuidString
            let outputFilePath = (NSTemporaryDirectory() as NSString).appendingPathComponent((outputFileName as NSString).appendingPathExtension("mov")!)
            movieOutput.startRecording(to: URL(fileURLWithPath: outputFilePath), recordingDelegate: self)

        }
        else {
            stopRecording()
        }
    }

    func stopRecording() {
        if movieOutput.isRecording == true {
            animator?.pauseAnimation()
            movieOutput.stopRecording()
        }
    }
    @IBAction func unwindToCamera(sender: UIStoryboardSegue) {
    }
    ...
}

extension CameraViewController: AVCaptureFileOutputRecordingDelegate{
    func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {
        if (error != nil) {
            print("Error recording movie: \(error!.localizedDescription)")
        } else {
            self.footageURL = outputFileURL as URL
            //print(self.videoRecorded!)
            self.performSegue(withIdentifier: "TrimFootage_Segue", sender: nil)
        }
    }
    override func prepare(for segue: UIStoryboardSegue, sender: Any?){
        if segue.identifier == "TrimFootage_Segue" {
            let controller = segue.destination as! TrimFootageViewController
            controller.footageURL = self.footageURL
        }
    }
}

因此，如果它不存在，它会创建一个动画器，然后调用 startRecording 来启动动画。然后 stopRecording 停止它。然后，当视频完成录制到输出文件时，它会转到 newView 控制器。当我按下该视图控制器时，它会使用展开 segue - unwindToCameraWithSender:

当我放松并回到相机时，视频不是在录制，而是在播放动画。什么可能导致该动画重新开始？我怎样才能防止这种情况？

【问题讨论】：

标签： ios swift uiviewanimation uiviewpropertyanimator

【解决方案1】：

我认为动画只是被暂停是原因。在stopRecording()方法中试试

animator?.stopAnimation(true)

而不是

animator?.pauseAnimation()

【讨论】：

【解决方案2】：

所以我做了一件事来解决这个问题，但没有解决它是像这样使用 UIDynamicAnimator：

@objc func handleTap(_ gesture:UITapGestureRecognizer) {
        startRecording()

        if let rotate = rotate{
            animator.removeBehavior(rotate)
            self.rotate = nil
        } else {
            rotate = UIDynamicItemBehavior(items: [self.recordingSpinner])
            rotate?.allowsRotation = true
            rotate?.angularResistance = 0
            rotate?.addAngularVelocity(1, for: self.recordingSpinner)
            animator.addBehavior(rotate!)
        }
    }

取自这个答案：Proper way to stop an infinitely rotating image? and how does one implement removeAllAnimations?

有趣的是，虽然我不确定为什么，但当我执行 segue 时似乎没有开始旋转。如果有人对我为什么喜欢听他们有想法

【讨论】：