ios - 当我将滚动方向从垂直更改为水平时,为什么集合视图会崩溃?
问题描述
我有一个集合视图,它显示了我传递给它的任何数据对象的一组视频。当您在内容视图中按下其中一个视频时,会出现一个新视图 (DetailViewController),并且视频会以更详细的视图显示。在那个 DetailViewController 中有一个后退按钮,可以关闭视图并将您带回带有集合视图的主页 - 这是发生崩溃时,当我从那个 'DetailViewController' 返回主视图控制器时。
当集合视图的“滚动方向”设置为垂直时,一切正常,但是当我将其设置为水平(这是我想要的)时,它会像上面解释的那样崩溃。
崩溃是:
Unexpectedly found nil while unwrapping an Optional value
来源是:
private func findCurrentCell(path: IndexPath) -> UICollectionViewCell {
return playerCollect.cellForItem(at: path)!
}
我猜当用户滚动path
时IndexPath
索引没有更新,所以索引没有更新?
有任何想法吗?如果需要,我可以提供视频或一些额外的代码。
编辑(额外代码):
import UIKit
import AVFoundation
import MMPlayerView
class ViewController: UIViewController {
var offsetObservation: NSKeyValueObservation?
lazy var mmPlayerLayer: MMPlayerLayer = {
let l = MMPlayerLayer()
l.cacheType = .memory(count: 5)
l.coverFitType = .fitToPlayerView
l.videoGravity = AVLayerVideoGravity.resizeAspect
l.replace(cover: CoverA.instantiateFromNib())
l.repeatWhenEnd = true
return l
}()
@IBOutlet weak var playerCollect: UICollectionView!
override func viewDidLoad() {
super.viewDidLoad()
// remove previous download fails file
MMPlayerDownloader.cleanTmpFile()
self.navigationController?.mmPlayerTransition.push.pass(setting: { (_) in
})
offsetObservation = playerCollect.observe(\.contentOffset, options: [.new]) { [weak self] (_, value) in
guard let self = self, self.presentedViewController == nil else {return}
NSObject.cancelPreviousPerformRequests(withTarget: self)
self.perform(#selector(self.startLoading), with: nil, afterDelay: 0.2)
}
playerCollect.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: 200, right:0)
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) { [weak self] in
self?.updateByContentOffset()
self?.startLoading()
}
mmPlayerLayer.getStatusBlock { [weak self] (status) in
switch status {
case .failed(let err):
let alert = UIAlertController(title: "err", message: err.description, preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
self?.present(alert, animated: true, completion: nil)
case .ready:
print("Ready to Play")
case .playing:
print("Playing")
case .pause:
print("Pause")
case .end:
print("End")
default: break
}
}
mmPlayerLayer.getOrientationChange { (status) in
print("Player OrientationChange \(status)")
}
}
deinit {
offsetObservation?.invalidate()
offsetObservation = nil
print("ViewController deinit")
}
}
func backReplaceSuperView(original: UIView?) -> UIView? {
guard let path = self.findCurrentPath() else {
return original
}
let cell = self.findCurrentCell(path: path) as! PlayerCell
return cell.imgView
}
// add layer to temp view and pass to another controller
var passPlayer: MMPlayerLayer {
return self.mmPlayerLayer
}
func transitionWillStart() {
}
// show cell.image
func transitionCompleted() {
self.updateByContentOffset()
self.startLoading()
}
}
extension ViewController: UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let m = min(UIScreen.main.bounds.size.width, UIScreen.main.bounds.size.height)
return CGSize(width: m, height: m*0.75)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
DispatchQueue.main.async { [unowned self] in
if self.presentedViewController != nil || self.mmPlayerLayer.isShrink == true {
//self.playerCollect.scrollToItem(at: indexPath, at: .centeredVertically, animated: true)
//self.updateDetail(at: indexPath)
} else {
self.presentDetail(at: indexPath)
}
}
}
fileprivate func updateByContentOffset() {
if mmPlayerLayer.isShrink {
return
}
if let path = findCurrentPath(),
self.presentedViewController == nil {
self.updateCell(at: path)
//Demo SubTitle
if path.row == 0, self.mmPlayerLayer.subtitleSetting.subtitleType == nil {
let subtitleStr = Bundle.main.path(forResource: "srtDemo", ofType: "srt")!
if let str = try? String.init(contentsOfFile: subtitleStr) {
self.mmPlayerLayer.subtitleSetting.subtitleType = .srt(info: str)
self.mmPlayerLayer.subtitleSetting.defaultTextColor = .red
self.mmPlayerLayer.subtitleSetting.defaultFont = UIFont.boldSystemFont(ofSize: 20)
}
}
}
}
fileprivate func presentDetail(at indexPath: IndexPath) {
self.updateCell(at: indexPath)
mmPlayerLayer.resume()
if let vc = UIStoryboard.init(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "DetailViewController") as? DetailViewController {
vc.data = DemoSource.shared.demoData[indexPath.row]
self.present(vc, animated: true, completion: nil)
}
}
fileprivate func updateCell(at indexPath: IndexPath) {
if let cell = playerCollect.cellForItem(at: indexPath) as? PlayerCell, let playURL = cell.data?.play_Url {
// this thumb use when transition start and your video dosent start
mmPlayerLayer.thumbImageView.image = cell.imgView.image
// set video where to play
mmPlayerLayer.playView = cell.imgView
mmPlayerLayer.set(url: playURL)
}
}
@objc fileprivate func startLoading() {
self.updateByContentOffset()
if self.presentedViewController != nil {
return
}
// start loading video
mmPlayerLayer.resume()
}
private func findCurrentPath() -> IndexPath? {
let p = CGPoint(x: playerCollect.frame.width/2, y: playerCollect.contentOffset.y + playerCollect.frame.width/2)
return playerCollect.indexPathForItem(at: p)
}
private func findCurrentCell(path: IndexPath) -> UICollectionViewCell {
return playerCollect.cellForItem(at: path)!
}
}
extension ViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return DemoSource.shared.demoData.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "PlayerCell", for: indexPath) as? PlayerCell {
cell.data = DemoSource.shared.demoData[indexPath.row]
return cell
}
return UICollectionViewCell()
}
}
解决方案
使用强制可选运算符是不好的做法,!
因为它通常会导致您描述的错误消息。您的findCurrentPath
计算尚未针对水平移动进行更新。首先,将您的findCurrentPath
方法更改为(我相信您正在努力实现的目标):
private func findCurrentPath() -> IndexPath? {
let p = CGPoint(x: playerCollect.contentOffset.x + playerCollect.frame.width/2,
y: playerCollect.frame.height/2)
return playerCollect.indexPathForItem(at: p)
}
为了防止崩溃,即使它没有完全按照您的意愿进行操作,我也只清理了其他两种方法,因为有太多强制可选运算符来解决它们;将您的findCurrentCell
方法更改为以下内容:
private func findCurrentCell(path: IndexPath) -> UICollectionViewCell? {
return playerCollect.cellForItem(at: path)
}
最后是您的backReplaceSuperView
方法:
func backReplaceSuperView(original: UIView?) -> UIView? {
guard let path = self.findCurrentPath(),
let cell = self.findCurrentCell(path: path) as? PlayerCell else {
return original
}
return cell.imgView
}
推荐阅读
- cypress - 赛普拉斯有没有办法检查开放请求?
- python - 返回值和跟踪内部状态时如何使用 Python super()?
- installation - 使复选框的行为类似于单选按钮,但默认选择其中一个部分 - NSIS 组件页面
- bash - 如何使 apt 假设是并强制 bash 脚本中的所有安装是
- python - 在一个非常大的表上对 Google Cloud SQL 的超慢 SQLAlchemy 查询
- amazon-cloudformation - 如何使用 AWS CloudFormation 模板更正此错误
- javascript - 如何使用新文件中的内容更改网页上的 SVG 元素?
- angular - Vendor.js 文件节点模块拆分成块
- reactjs - TypeError:无法读取未定义的属性“primaryColor”-Typescript,样式化组件(tsx)
- ios - AudioKit v5 如何在同一个输入节点上使用 AmplitudeTap 和 NodeRecorder