问题描述
背景
我正在实现一个应该公开 play、pause mute 和 unmute 函数的视频播放器。在我的情况下，如果这些布尔设置作为绑定传入，那将是理想的。我有一个基本的 UIViewRepresentable 在这里工作：
import SwiftUI
import AVKit
import UIKit
//MARK:- video player with play/pause API
struct MediaPlayerFeedItem : UIViewControllerRepresentable {
var urls: [String]
@Binding var shouldplay: Bool
@Binding var shouldMute: Bool
var vc = AVPlayerViewController()
@State var pauseAll: Bool = false
//MARK:- API
// @use: play from beginning
func play(){
self._goPlay()
}
// @use: pause video
func pause(){
vc.player?.pause()
}
// @use respond to mute event
func mute(){
}
// @use: respond to umute event
func unmute(){
}
//MARK:- view
func makeUIViewController(context: Context) -> AVPlayerViewController {
if shouldplay {
_goPlay()
} else {
let items = _makeItems()
if items.count > 0 {
let player = AVQueuePlayer(items: items)
vc.player = player
vc.showsPlaybackControls = false
vc.videoGravity = .resizeAspectFill
vc.player?.seek(to: .zero)
vc.player?.pause()
}
}
return vc
}
// @use: this fn will fire when `shouldplay` is updated. at which point you can
// `play` or `pause` the video as desired
func updateUIViewController(_ uiViewController: AVPlayerViewController,context: Context) {
}
//MARK:- playback
private func _goPlay(){
let items = _makeItems()
guard items.count > 0 else { return }
let player = AVQueuePlayer(items: items)
vc.player = player
vc.showsPlaybackControls = false
vc.videoGravity = .resizeAspectFill
vc.player?.seek(to: .zero)
vc.player?.play()
NotificationCenter.default
.addobserver(
forName: NSNotification.Name.AVPlayerItemDidplayToEndTime,object: items[items.count-1],queue: .main
){_ in
self._goPlay()
}
}
// @use: make a new set of avplayeritems before each
// invocation of _goPlay loop
private func _makeItems() -> [AVPlayerItem] {
return urls
.map{ URL(string: $0) }
.filter{ $0 != nil }
.map{ AVPlayerItem(url: $0!) }
}
}
使用：
MediaPlayerFeedItem(urls: [url1,url2],shouldplay: $shouldplay,shouldMute: .constant(true) )
问题是我不确定如何将 UIViewRepresentable 与其绑定值连接起来。也就是说，当 shouldplay 变为 true 时，如果 MediaPlayerFeedItem 仅自行调用 play() 会很好。
================================================ ====
更新
我忘了提到，在较早的实现中，我有这个：
func updateUIViewController(_ uiViewController: AVPlayerViewController,context: Context) {
if shouldplay {
play()
} else {
pause()
}
}
这就是 MediaPlayerFeedItem 的行为真正令人困惑的地方。 updateViewController 及其各自的函数都按预期调用 play 或 pause 触发，但在播放或暂停视频方面似乎没有任何作用。
例如，如果 init MediaPlayerFeedItem 和 shouldplay 设置为真值绑定，则无论稍后发生的暂停命令如何，视频都会播放。如果我将 MediaPlayerFeedItem 初始化为 shouldplay 设置为 false 绑定，然后再次将其设置为 true，则视频根本无法播放。视频加载，它只是在第一帧暂停。
我倾向于说问题出在 _goPlay 函数本身，但是如果我只是在 _goPlay 函数中运行 makeUIViewController，无论 shouldplay {1}} 设置为 true。
根据@aheze 的建议，我在 play、pause 和 _goPlay 函数中添加了打印语句，行为如下：@aheze when I init MediaFeedItem with false绑定，我在初始化时得到 3 个 pausing 打印。然后 10 秒后，当我将 shouldplay 设置为 true 时，我得到一个 play 打印语句，并且没有后续的 pause 语句。有趣的是，我也从 loop play 调用中的 _goPlay 函数中获得了 NotificationCenter 打印语句，所以这意味着视频正在播放......它只是没有呈现。请注意，我正在每个循环中初始化所有新的 AVPlayerItem 列表，这是必需的，因为我无法在不同的播放循环中共享它们。
解决方法
请务必查看评论：
// @use: this fn will fire when `shouldPlay` is updated. at which point you can
// `play` or `pause` the video as desired
func updateUIViewController(_ uiViewController: AVPlayerViewController,context: Context) {
正如评论所说，每当 shouldPlay 更新时，updateUIViewController 都会被调用。所以，你可以这样做：
func updateUIViewController(_ uiViewController: AVPlayerViewController,context: Context) {
if shouldPlay {
play()
} else {
pause()
}
}
想通了：
struct VideoPlayerView: UIViewRepresentable {
var urls: [URL]
var playOnLoad: Bool
@EnvironmentObject var appState: AppState
func makeUIView(context: Context) -> UIView {
return PlayerUIViewQueue(urls: urls,playOnLoad: playOnLoad,frame: .zero)
}
// @use: on `appState` context change,`play` `pause` or `resume` the video
func updateUIView(_ uiView: UIView,context: UIViewRepresentableContext<VideoPlayerView>) {
if let uiv = uiView as? PlayerUIViewQueue {
switch appState.getTokenPlayCommand() {
case .pause:
uiv.pause()
case .play:
uiv.playFromBeginning()
case .resume:
uiv.resume()
}
}
}
}
class PlayerUIViewQueue: UIView {
private var URLs: [URL]
// player references
private let playerLayer = AVPlayerLayer()
private var current_mutli : AVQueuePlayer? = nil
private var current_single: AVPlayer? = nil
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func layoutSubviews() {
super.layoutSubviews()
playerLayer.frame = bounds
}
init(urls: [URL],playOnLoad:Bool,frame: CGRect){
self.URLs = urls
super.init(frame: frame)
if self.URLs.count == 1 {
print("if case")
initSinglePlayer()
} else {
print("else case")
loopAll()
}
}
//MARK:- API
func resume(){
print("RESUMNING")
current_mutli?.play()
current_single?.play()
}
func pause(){
print("PAUSING")
current_mutli?.pause()
current_single?.pause()
}
func playFromBeginning(){
print("playFromBeginning")
current_mutli?.seek(to: .zero)
current_mutli?.play()
current_single?.seek(to: .zero)
current_single?.play()
}
//MARK:- player utils
private func initSinglePlayer(){
if URLs.count == 0 { return }
let player = AVPlayer(url: URLs[0])
player.actionAtItemEnd = .none
self.current_single = player
playerLayer.player = player
playerLayer.videoGravity = .resizeAspectFill
layer.addSublayer(playerLayer)
player.play()
NotificationCenter.default
.addObserver(
self,selector: #selector(loopPlayerSingle(notification:)),name: .AVPlayerItemDidPlayToEndTime,object: player.currentItem
)
}
@objc func loopPlayerSingle(notification: Notification) {
if let playerItem = notification.object as? AVPlayerItem {
playerItem.seek(to: .zero,completionHandler: nil)
}
}
// @use: on each `loopAll()` invocation,reinit
// the player with all video `items`
private func loopAll(){
let items = URLs.map{ AVPlayerItem.init(url: $0) }
let player = AVQueuePlayer(items: items)
self.playerLayer.player = player
self.current_mutli = player
player.seek(to: .zero)
player.play()
playerLayer.videoGravity = .resizeAspectFill
layer.addSublayer(playerLayer)
NotificationCenter.default
.addObserver(
self,selector: #selector(loopPlayerMulti(notification:)),object: player.items().last
)
}
@objc private func loopPlayerMulti(notification: Notification) {
loopAll()
}
}