[英]swift ask music permission for initial view controller
我有一個拆分視圖控制器,其頂視圖控制器設置為表視圖控制器,該控制器用於顯示播放列表列表供選擇。 首次加載應用程序時,它會請求音樂訪問權限。 回答“是”確實會授予它權限,但表視圖不顯示任何播放列表。 我最終不得不殺死該應用程序並再次運行。 我是在錯誤的位置申請音樂庫許可嗎? 正是在該頂部視圖控制器的viewWillAppear中,並將我正在使用的播放列表(因為某些播放列表被篩選掉)存儲在一個播放列表中。
override func viewWillAppear(_ animated: Bool) {
self.clearsSelectionOnViewWillAppear = self.splitViewController!.isCollapsed
super.viewWillAppear(animated)
checkMediaAccessAndSetup()
}
func checkMediaAccessAndSetup() {
let authorizationStatus = MPMediaLibrary.authorizationStatus()
switch authorizationStatus {
case .notDetermined:
// Show the permission prompt.
MPMediaLibrary.requestAuthorization({[weak self] (newAuthorizationStatus: MPMediaLibraryAuthorizationStatus) in
// Try again after the prompt is dismissed.
self?.checkMediaAccessAndSetup()
})
case .denied, .restricted:
// Do not use MPMediaQuery.
return
default:
// Proceed as usual.
break
}
// Do stuff with MPMediaQuery
self.setupPlaylistStore()
tableView.reloadData()
}
您的代碼的主要問題是
您完全無法解決在后台線程上調用requestAuthorization
完成函數這一事實。 您需要跳出主線程才能在接口上工作。
您已省略了所有重要的.authorized
案例。 當你有工作要做,這取決於你的授權狀態,你必須現在就做,如果你被授權,但授權后,如果您沒有確定。
因此,這是進行一致性授權檢查的正確方案(其中f()
是您可能總是想做的事情):
let status = MPMediaLibrary.authorizationStatus()
switch status {
case .authorized:
f()
case .notDetermined:
MPMediaLibrary.requestAuthorization() { status in
if status == .authorized {
DispatchQueue.main.async {
f()
}
}
}
// ...
}
如果將代碼抽象為實用工具方法,其中f
可以是任意值,則可以在應用程序中可能需要授權的任何地方進行此操作-不僅僅是在啟動時。
感謝您的評論,它為我提供了正在進行的多線程的線索,並且如果類中沒有播放列表可以繼續檢查並重新加載表數據,我可以通過計時器調用對其進行修復。
override func viewWillAppear(_ animated: Bool) {
self.clearsSelectionOnViewWillAppear = self.splitViewController!.isCollapsed
super.viewWillAppear(animated)
checkMediaAccess()
self.setupPlaylistStore()
tableView.reloadData()
if store.allPlaylists.count < 1 {
playlistTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(self.playlistTimerCall), userInfo: nil, repeats: true)
}
}
@objc func playlistTimerCall() {
self.setupPlaylistStore()
if store.allPlaylists.count > 1 {
tableView.reloadData()
playlistTimer?.invalidate()
}
}
func checkMediaAccess() {
let authorizationStatus = MPMediaLibrary.authorizationStatus()
switch authorizationStatus {
case .notDetermined:
// Show the permission prompt.
MPMediaLibrary.requestAuthorization({[weak self] (newAuthorizationStatus: MPMediaLibraryAuthorizationStatus) in
// Try again after the prompt is dismissed.
self?.checkMediaAccess()
})
case .denied, .restricted:
// Do not use MPMediaQuery.
return
default:
// Proceed as usual.
break
}
}
func setupPlaylistStore() {
// purge store
store.clearAllPlaylists()
// create a query of media items in playlist
let myPlayListsQuery = MPMediaQuery.playlists()
if myPlayListsQuery.collections != nil {
playlists = myPlayListsQuery.collections!
}
// add playlists to MyPlaylist(s)
if playlists.count > 0 {
for index in 0...playlists.count - 1 {
let playlist = playlists[index]
store.addPlaylist(playlist: playlist as! MPMediaPlaylist)
}
}
var toBeRemoved = [Int]()
let defaults = UserDefaults.standard
if defaults.bool(forKey: "exclude_smart_playlists") {
//smart
for index in 0...(playlists.count - 1) {
let playlist = playlists[index]
let theAttributes = playlist.value(forProperty: MPMediaPlaylistPropertyPlaylistAttributes) as! Int
if theAttributes == 2 {
toBeRemoved.append(index)
}
}
}
if defaults.bool(forKey: "exclude_folders") {
//folders
for index in 0...(playlists.count - 1) {
let playlist = playlists[index]
let isFolder = playlist.value(forProperty: "isFolder")
let stringIsFolder = String("\(String(describing: isFolder))")
if ((stringIsFolder.range(of: "1")) != nil) {
toBeRemoved.append(index)
}
}
}
//sort from the last to the first so i don't reindex
let reverseSortedPlaylists = toBeRemoved.sorted(by: >)
// remove the unwanted playlists
for list in reverseSortedPlaylists {
store.removePlaylist(index: list)
}
}
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