Android开发：如何使用MediaStore实现本地歌曲RecyclerView列表展示（附代码求指导）

Hey there! Let's walk through your code and fix the gaps to get your song list working properly. You're on the right track with MediaStore, but there are a few key things missing and some tweaks needed.

1. Missing Permissions to Access Media Files #

First off, you need to request the necessary permissions to read audio files from the device.

• For Android 13 (API 33+): Use READ_MEDIA_AUDIO permission.
• For Android 12 and below: Use READ_EXTERNAL_STORAGE permission.

Add these to your AndroidManifest.xml:

<!-- For Android 12 and below -->
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" android:maxSdkVersion="32" />
<!-- For Android 13+ -->
<uses-permission android:name="android.permission.READ_MEDIA_AUDIO" />

Then, request the permission at runtime before querying songs. Add this code to your MainActivity:

private fun checkPermissions() {
    val requiredPermission = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
        Manifest.permission.READ_MEDIA_AUDIO
    } else {
        Manifest.permission.READ_EXTERNAL_STORAGE
    }

    if (ContextCompat.checkSelfPermission(this, requiredPermission) != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this, arrayOf(requiredPermission), 100)
    } else {
        initSongs()
    }
}

// Handle permission grant/deny result
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    if (requestCode == 100 && grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
        initSongs()
    } else {
        Toast.makeText(this, "Permission required to access songs", Toast.LENGTH_SHORT).show()
    }
}

Replace your initSongs() call in onCreate with checkPermissions().

2. Fix Data Type Mismatches #

Your Song data class uses incorrect types for media attributes:

• MediaStore.Audio.Media.DURATION is a Long (milliseconds), not Float.
• MediaStore.Audio.Media.SIZE is a Long (file size in bytes), not String.

Update your Song data class:

data class Song(
    val uri: Uri,
    val name: String,
    val duration: Long, // Changed to Long
    val size: Long      // Changed to Long
)

Adjust the query code to fetch correct types:

val duration = cursor.getLong(durationColumn) // Use getLong instead of getFloat
val size = cursor.getLong(sizeColum)         // Use getLong instead of getString

Later, you can add helper functions to convert duration to mm:ss format and size to KB/MB for display.

3. Update RecyclerView Adapter After Loading Data #

Right now, your adapter initializes with an empty list and never gets notified when mSongs updates. Also, avoid GlobalScope (it's not lifecycle-aware) — use lifecycleScope instead:

Modify initSongs():

private fun initSongs() {
    lifecycleScope.launch {
        mSongs = querySongs()
        // Notify adapter of new data
        mSongAdapter.updateSongs(mSongs)
        Log.i("Canciones:", mSongs.toString()) // Log here instead of onStop
    }
}

Add an update method to your SongAdapter:

class SongAdapter(private var songs: List<Song>) : RecyclerView.Adapter<SongAdapter.SongViewHolder>() {
    // Implement your ViewHolder and bind logic here...

    fun updateSongs(newSongs: List<Song>) {
        songs = newSongs
        notifyDataSetChanged() // Use DiffUtil for more efficient updates later
    }
}

4. Remove Unnecessary Android Version Check #

Your query logic is wrapped in an Android O+ check, but MediaStore queries work the same on older versions. Remove the check to support all devices:

private suspend fun querySongs(): List<Song> {
    val songs = mutableListOf<Song>()
    withContext(Dispatchers.IO) {
        val projection = arrayOf(
            MediaStore.Audio.Media._ID,
            MediaStore.Audio.Media.DISPLAY_NAME,
            MediaStore.Audio.Media.DURATION,
            MediaStore.Audio.Media.SIZE
        )

        // Optional: Filter to only music files (exclude ringtones/notifications)
        val selection = "${MediaStore.Audio.Media.IS_MUSIC} != 0"

        application.contentResolver.query(
            MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
            projection,
            selection,
            null,
            "${MediaStore.Audio.Media.DISPLAY_NAME} ASC" // Optional: Sort by name
        )?.use { cursor ->
            val idColumn = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media._ID)
            val nameColumn = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME)
            val durationColumn = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DURATION)
            val sizeColum = cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.SIZE)

            while (cursor.moveToNext()) {
                val id = cursor.getLong(idColumn)
                val name = cursor.getString(nameColumn)
                val duration = cursor.getLong(durationColumn)
                val size = cursor.getLong(sizeColum)
                val contentUri = ContentUris.withAppendedId(
                    MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
                    id
                )
                val song = Song(contentUri, name, duration, size)
                songs += song
            }
        }
    }
    return songs
}

Final Tips #

• Ensure your SongAdapter properly binds song data (like formatted duration/size) to your list item layout.
• For better performance, replace notifyDataSetChanged() with DiffUtil once your app is stable.

With these changes, your RecyclerView should correctly display all music files on the device!

内容的提问来源于stack exchange，提问作者CuadCode