ios - 当我使用属性更新视图时,ObservedObject 会重置。因此会导致数据丢失
问题描述
我有一个问题,ViewModel
当视图更新时会重新初始化。
我有 2 个视图,SongListView
它们PlayerView
共享一个Player
. 当玩家的 Playing 状态改变(isPlaying == true)
时,viewModel
inSongListView
重置并变成空数组。因此,我视图上的列表变为空。
歌曲列表视图:
struct SongListView: View {
@ObservedObject var model: SongListViewModel = SongListViewModel() // This resets when player.isPlaying is set to true
@ObservedObject var player: Player
var body: some View {
List(model.songs, id: \.id) { song in
Button(action: {
self.player.play(link: song.link)
}) {
TitleRowView(title: song)
}
}
.onAppear {
self.model.get()
}
.navigationBarTitle(Text("Songs"), displayMode: .inline)
}
}
歌曲列表视图模型:
class SongListViewModel: ObservableObject {
@Published var songs: [Song] = [Song(id: 2, name: "ish", link: "ishm")] // When I tap the row, the songs var is re-initialized
func get() {
guard let url = URL(string: "apiPath") else { return }
URLSession(configuration: URLSessionConfiguration.default).dataTask(with: url) {data, response, error
// Some more code
self.songs = data
}.resume()
}
}
播放器视图:
struct PlayerView: View {
@ObservedObject var player: Player
var body: some View {
HStack {
Button(action: {
if self.player.isPlaying {
self.player.pause()
} else {
self.player.play()
}
}) {
// This change causes the viewModel to reset to empty array
if self.player.isPlaying {
Image(systemName: "pause.fill")
.resizable()
} else {
Image(systemName: "play.fill")
.resizable()
}
}
}
}
}
玩家:
class Player : ObservableObject
{
@Published var isPlaying: Bool = false
private var player: AVPlayer?
// This method is called when the user taps on a row in List
func play(link: String) {
guard let url = URL(string: link) else { return }
let playerItem = AVPlayerItem(url: url)
player = AVPlayer(playerItem: playerItem)
player?.play()
isPlaying = true // If I comment this line, the songs list in viewModel does not changes
}
}
提前致谢!
更新:仍然不起作用
struct SongListView: View {
@ObservedObject var model: SongListViewModel
var body: some View {
// View
}
}
struct CategoryListView: View {
var categoryData : [Category]
@ObservedObject var player: Player
var body: some View {
List(categoryData, id: \.id) { category in
if category.id == 3 {
NavigationLink(destination: SongListView(model: SongListViewModel(), player: self.player)) {
TitleRowView(title: category)
}
}
}
}
}
解决方案
使用@StateObject
而不是@ObservedObject
为我工作。
@StateObject
只要需要视图,标记为的属性将保留其最初分配的 ObservedObject 实例,即使结构被 SwiftUI 重新创建。
这允许您维护 ObservedObject 数据的状态。
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