我正在创建一个用于学习的音乐播放器，并想使用接口和I将活动容器中的歌曲列表传递给与之关联的6个片段（即专辑，艺术家，歌曲，流派，播放列表，MyFiles）已使用共享首选项存储了歌曲列表，因为我不想为每个片段创建单独的光标。
但是由于我首先意识到，由于首先调用viewpageradapter会导致片段生命周期，并且初始化了其所有资源，因此遇到了与传递列表有关的错误。
现在，由于我认为是在活动生命周期结束时调用的权限处理程序，因此所有逻辑都是针对因已创建片段而浪费的歌曲列表编写的。因此，有时歌曲列表会显示为片段，有时却不会。
现在我有以下问题
1.我使用的方法错误吗？
2.还是我的代码需要更改？
3.在这种情况下，共享首选项是否正确？
MainActivity
class MainActivity : AppCompatActivity() {
private val tabLayout by binder<TabLayout>(R.id.tabs)
private val viewPager by binder<ViewPager>(R.id.viewpager)
private var msongListener: OnSongReceivedListener? = null
lateinit var readWriteSongPermissionHandler : RequestPermissionHandler
var songList:MutableList<BeatDto> = mutableListOf()
lateinit var songManager: SongManager
var sharedPreferences: SharedPreferences? = null
lateinit var editor: SharedPreferences.Editor
var file= Environment.getDataDirectory()
val storage_check_pref="intent_memory"
val song_list_pref="intent_songs"
var current_memory:Float=0.0f
val context = this
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
sharedPreferences = context.getSharedPreferences("beat_drop", Context.MODE_PRIVATE);
if(sharedPreferences?.getString(storage_check_pref,"").equals("success")){
current_memory=SongManager.megaBytesAvailable(file)
}
setPermissionsandGetSongDetails()
setupViewPager(viewPager)
changeSelectedTabSize(tabLayout,viewPager,this)
tabLayout.setupWithViewPager(viewPager)
}
interface OnSongReceivedListener {
fun onPassSongs(listSongs: MutableList<BeatDto>)
}
fun setAboutDataListener(listener: OnSongReceivedListener) {
msongListener = listener
msongListener?.onPassSongs(songList)
}
fun setupViewPager(viewPager: ViewPager){
val adapter = ViewPagerAdapter(supportFragmentManager)
adapter.addFragment(AlbumFragment(),"Albums")
adapter.addFragment(ArtistFragment(),"Artists")
adapter.addFragment(SongFragment(),"Songs")
adapter.addFragment(GenreFragment(),"Genres")
adapter.addFragment(PlaylistFragment(),"Playlists")
adapter.addFragment(MyFileFragment(),"My Files")
viewPager.adapter=adapter
viewPager.currentItem = 3
viewPager.setOffscreenPageLimit(6);
}
fun changeSelectedTabSize(tabLayout:TabLayout,viewPager: ViewPager, context: Context?){
for(i in 0 until tabLayout.tabCount){
val tab:TabLayout.Tab?= tabLayout.getTabAt(i)
val tabTextView:TextView?=TextView(context)
tab?.customView = tabTextView
tabTextView?.layoutParams?.width=ViewGroup.LayoutParams.WRAP_CONTENT
tabTextView?.layoutParams?.height=ViewGroup.LayoutParams.WRAP_CONTENT
tabTextView?.text = tab?.text
if(i==0){
tabTextView?.textSize = 18f
}
}
val listener:TabLayout.TabLayoutOnPageChangeListener=TabLayout.TabLayoutOnPageChangeListener(tabLayout)
viewPager.addOnPageChangeListener(listener)
tabLayout.addOnTabSelectedListener(object:TabLayout.OnTabSelectedListener{
override fun onTabSelected(tab: TabLayout.Tab?) {
val vg:ViewGroup=tabLayout.getChildAt(0) as ViewGroup
val vgTab:ViewGroup=vg.getChildAt(tab?.position!!) as ViewGroup
val tabChildsCount:Int=vgTab.childCount
for (i in 0 until tabChildsCount){
val tabViewChild:View=vgTab.getChildAt(i)
if (tabViewChild is TextView)
tabViewChild.setTextSize(35.0f)
}
}
override fun onTabUnselected(tab: TabLayout.Tab?) {
val vg:ViewGroup=tabLayout.getChildAt(0) as ViewGroup
val vgTab:ViewGroup=vg.getChildAt(tab!!.position) as ViewGroup
val tabChildsCount:Int=vgTab.childCount
for (i in 0 until tabChildsCount){
val tabViewChild:View=vgTab.getChildAt(i)
if (tabViewChild is TextView)
tabViewChild.textSize = 8f
}
}
override fun onTabReselected(p0: TabLayout.Tab?) {
}
})
}
fun setPermissionsandGetSongDetails(){
try {
readWriteSongPermissionHandler= RequestPermissionHandler(this@MainActivity,
permissions = setOf(Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE),
listener = object: RequestPermissionHandler.Listener{
override fun onComplete(grantedPermissions: Set<String>, deniedPermissions: Set<String>) {
if(grantedPermissions.isNotEmpty()){
if (current_memory< SongManager.megaBytesAvailable(file)){
songManager= SongManager()
songList=songManager.getPlayList(context)
editor= sharedPreferences!!.edit()
editor.putString(storage_check_pref,"success")
editor.putString(song_list_pref, Gson().toJson(songList).toString())
editor.commit()
}else{
songList= Gson().fromJson(sharedPreferences?.getString(song_list_pref,""),
Array<BeatDto>::class.java).toMutableList()
}
}else if(deniedPermissions.isNotEmpty()){
Toast.makeText(context, "Permission Denied Already", Toast.LENGTH_SHORT).show()
}
}
override fun onShowPermissionRationale(permissions: Set<String>): Boolean {
AlertDialog.Builder(this@MainActivity).setMessage("To able to Listen Music, we need Read and Write permission")
.setPositiveButton("OK") { _, _ ->
readWriteSongPermissionHandler.retryRequestDeniedPermission()
}
.setNegativeButton("Cancel") { dialog, _ ->
readWriteSongPermissionHandler.cancel()
dialog.dismiss()
}
.show()
return true
}
override fun onShowSettingRationale(permissions: Set<String>): Boolean {
AlertDialog.Builder(this@MainActivity).setMessage("Go Settings -> Permission. " + "Make SMS on and Storage on")
.setPositiveButton("Settings") { _, _ ->
readWriteSongPermissionHandler.requestPermissionInSetting()
}
.setNegativeButton("Cancel") { dialog, _ ->
readWriteSongPermissionHandler.cancel()
dialog.cancel()
}
.show()
return true
}
})
readWriteSongPermissionHandler.requestPermission()
}catch (ex:Exception){
ex.printStackTrace()
}
}
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>,
grantResults: IntArray) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults)
readWriteSongPermissionHandler.onRequestPermissionsResult(requestCode, permissions,
grantResults)
}
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
readWriteSongPermissionHandler.onActivityResult(requestCode)
}
internal inner class ViewPagerAdapter(manager: FragmentManager):FragmentPagerAdapter(manager){
private val mFragmentList=ArrayList<Fragment>()
private val mFragmentTitleList=ArrayList<String>()
override fun getItem(p0: Int): Fragment {
return mFragmentList[p0]
}
override fun getCount(): Int {
return mFragmentList.size
}
fun addFragment(fragment:Fragment,title:String){
mFragmentList.add(fragment)
mFragmentTitleList.add(title)
}
override fun getPageTitle(position: Int): CharSequence? {
return mFragmentTitleList[position]
}
}
}
SongFragment
class SongFragment : Fragment(){
lateinit var recyclerView:RecyclerView
lateinit var songAdapter: SongAdapter
lateinit var songManager: SongManager
var songList:MutableList<BeatDto> = mutableListOf()
lateinit var readWriteSongPermissionHandler : RequestPermissionHandler
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
val view:View = inflater.inflate(R.layout.fragment_song, container, false)
return view
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
recyclerView= view.findViewById(R.id.rr_songs)
recyclerView.layoutManager=LinearLayoutManager(activity,LinearLayoutManager.VERTICAL,false)
val spacingInPixels = resources.getDimensionPixelSize(R.dimen.mtrl_card_spacing)
recyclerView.addItemDecoration(SpacesItemDecoration(spacingInPixels))
recyclerView.adapter=songAdapter
recyclerView.setHasFixedSize(true)
}
override fun onResume() {
super.onResume()
val mActivity = activity as MainActivity
// mActivity.setAboutDataListener(this)
mActivity.setAboutDataListener(object : MainActivity.OnSongReceivedListener {
override fun onPassSongs(listSongs: MutableList<BeatDto>) {
songList=listSongs
}
})
songAdapter= SongAdapter(songList)
}
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
readWriteSongPermissionHandler.onActivityResult(requestCode)
}
}