Querying all audio files on an Android device yields no results

Question

This is my first time using Xamarin, so please bear with me.

I'm trying to create a music player app for Android that detects all music files on the user's device, lists them out, and lets the user play them.
This is part of the code I have for retrieving audio files:

string[] columns = {
    MediaStore.Audio.Media.InterfaceConsts.IsMusic,
    MediaStore.Audio.Media.InterfaceConsts.RelativePath,
    MediaStore.Audio.Media.InterfaceConsts.Title,
    MediaStore.Audio.Media.InterfaceConsts.Album,
    MediaStore.Audio.Media.InterfaceConsts.AlbumId,
    MediaStore.Audio.Media.InterfaceConsts.Artist,
    MediaStore.Audio.Media.InterfaceConsts.ArtistId,
};
Log.Info("Test", "Query start");
ICursor cursor = context?.ContentResolver?.Query(MediaStore.Audio.Media.ExternalContentUri, columns, null, null, null);
if (cursor is null)
{
    Log.Info("Test", "null");
    return;
}
while (cursor.MoveToNext())
{
    Log.Info("Test", "next");
    if (!Boolean.Parse(cursor.GetString(0)))
    {
        Log.Info("Test", "Not music");
        continue;
    }
    string trackPath = cursor.GetString(1);
    Log.Info("Test", trackPath);
}
Log.Info("Test", "Query end");

As a test, I uploaded 4 music files (.mp3) to my Android emulator and ran my app. The files are in SDCARD/Music.
Unfortunately, the query doesn't seem to contain any results. It prints out "Query start" and then immediately "Query end". From this I understand that it did not detect the files at all.

What am I doing wrong?

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

When I use MediaStore.Audio.Media.InterfaceConsts.RelativePath I get an exception about RelativePath do not existed in android 9.0 emulator, then I change it to MediaStore.Audio.Media.InterfaceConsts.Data like following code.

   public List<string> GetAudioFile()  
           {  
               List<string> vs = new List<string>();  
             Context  context= Android.App.Application.Context;  
     
               string[] columns = {  
                        MediaStore.Audio.Media.InterfaceConsts.IsMusic,  
                        MediaStore.Audio.Media.InterfaceConsts.Data,  
                        MediaStore.Audio.Media.InterfaceConsts.Title,  
                        MediaStore.Audio.Media.InterfaceConsts.Album,  
                        MediaStore.Audio.Media.InterfaceConsts.AlbumId,  
                        MediaStore.Audio.Media.InterfaceConsts.Artist,  
                        MediaStore.Audio.Media.InterfaceConsts.ArtistId,  
                         };  
               Log.Info("Test", "Query start");  
               ICursor cursor = context?.ContentResolver?.Query(MediaStore.Audio.Media.ExternalContentUri, columns, null, null, null);  
               if (cursor is null)  
               {  
                   Log.Info("Test", "null");  
                    
               }  
               while (cursor.MoveToNext())  
               {  
                   Log.Info("Test", "next");  
                   //if (!Boolean.Parse(cursor.GetString(0)))  
                   //{  
                   //    Log.Info("Test", "Not music");  
                   //    continue;  
                   //}  
                var Path=   cursor.GetString(cursor.GetColumnIndex(MediaStore.Audio.Media.InterfaceConsts.Data));  
                   string trackPath = cursor.GetString(1);  
                   vs.Add(trackPath);  
                   Log.Info("Test", trackPath);  
               }  
               Log.Info("Test", "Query end");  
     
               return vs;  
     
     
           }  

Note: If you want to read external file, you need to add following permission.

   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />  

And grand the permission at the runtime.

   public class MainActivity : Activity  
       {  
           protected override void OnCreate(Bundle savedInstanceState)  
           {  
               base.OnCreate(savedInstanceState);  
               //Open read permission.  
               if (ContextCompat.CheckSelfPermission(this, Manifest.Permission.ReadExternalStorage) != (int)Permission.Granted)  
               {  
                   RequestPermissions(new string[] { Manifest.Permission.ReadExternalStorage}, 0);  
               }  
                
           }  
   }  

==================
Update code===================

Here is my updated code.

   public List<string> GetAudioFile()  
           {  
               List<string> vs = new List<string>();  
             Context  context= Android.App.Application.Context;  
               
               string[] columns = {  
                        MediaStore.Audio.Media.InterfaceConsts.IsMusic,  
                        MediaStore.Audio.Media.InterfaceConsts.RelativePath,  
                         MediaStore.Audio.Media.InterfaceConsts.DisplayName,  
                        MediaStore.Audio.Media.InterfaceConsts.Title,  
                        MediaStore.Audio.Media.InterfaceConsts.Album,  
                        MediaStore.Audio.Media.InterfaceConsts.AlbumId,  
                        MediaStore.Audio.Media.InterfaceConsts.Artist,  
                        MediaStore.Audio.Media.InterfaceConsts.ArtistId,  
                         };  
               Log.Info("Test", "Query start");  
               ICursor cursor = context?.ContentResolver?.Query(MediaStore.Audio.Media.ExternalContentUri, columns, null, null, null);  
               if (cursor is null)  
               {  
                   Log.Info("Test", "null");  
                    
               }  
               while (cursor.MoveToNext())  
               {  
                   Log.Info("Test", "next");  
     
                    var Path=   cursor.GetString(cursor.GetColumnIndex(MediaStore.Audio.Media.InterfaceConsts.RelativePath));  
                   string MP3Name = cursor.GetString(cursor.GetColumnIndex(MediaStore.Audio.Media.InterfaceConsts.DisplayName));                       
                   string trackPath = Path + MP3Name;  
                   vs.Add(trackPath);  
                   Log.Info("Test", trackPath);  
               }  
               Log.Info("Test", "Query end");  
     
               return vs;  
           }  

Best Regards,

Leon Lu

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