我的申请是为了听音乐。我将在互联网上实现mvvm，然后是一个教程。但是，我发现它只用于在sqlite中保存和检索数据。当我删除一个mp3文件时，它只会删除songentity对象（它只是数据库中的一个信息行：标题、大小、艺术家等等）。但是我想删除mp3文件（二进制文件，真实文件，…）在mediastore中，在设备中，。。。你能告诉我解决这个问题的方法吗。我的想法是实现songdao接口，然后在其中编写deletefile（）函数，但我不知道如何编写它。
songentity.class类

@Entity(tableName = "song_table")
public class SongEntity implements Song {

public SongEntity() {
    Random random = new Random();
    songName = String.valueOf(random.nextDouble());
    id = random.nextInt();
}

@ColumnInfo(name = "song_name")
private String songName;

@ColumnInfo(name = "song_uri")
private String uriString;

@ColumnInfo(name = "path")
private String path;

@PrimaryKey (autoGenerate = true)
@ColumnInfo(name = "id")
private int id;

@ColumnInfo(name = "size")
private double size;

@ColumnInfo(name = "artist")
private String artist;

@ColumnInfo(name = "singer")
private String singer;

@Override
public void setSongName(String newName) {
    songName = newName;
}

@Override
public void setUriString(String newUriString) {
    uriString = newUriString;
}

@Override
public String getSongName() {
    return songName;
}

@Override
public String getUriString() {
    return uriString;
}

@Override
public String getPath() {
    return path;
}

@Override
public void setPath(String path) {
    this.path = path;
}

@Override
public int getId() {
    return id;
}

@Override
public void setId(int id) {
    this.id = id;
}

@Override
public double getSize() {
    return size;
}

@Override
public void setSize(double size) {
    this.size = size;
}

@Override
public String getArtist() {
    return artist;
}

@Override
public void setArtist(String artist) {
    this.artist = artist;
}

@Override
public String getSinger() {
    return singer;
}

@Override
public void setSinger(String singer) {
    this.singer = singer;
}

}
松岛级
@刀

public interface SongDAO {

@Insert(onConflict = OnConflictStrategy.REPLACE)
void insert(SongEntity songEntity);

@Update
void update(SongEntity songEntity);

@Delete
void delete(SongEntity songEntity);

@Query("DELETE FROM song_table")
void deleteAll();

@Query("SELECT * FROM song_table")
LiveData<List<SongEntity>> getAllSongs();

}
数据库.class

public abstract class SongDatabase extends RoomDatabase {
private static SongDatabase instance;

public abstract SongDAO songDAO();

public static synchronized SongDatabase getInstance(Context context) {
    if (instance == null) {
        instance = Room.databaseBuilder(context,
                SongDatabase.class,
                "song_database")
                .fallbackToDestructiveMigration()
                .build();
    }
    return  instance;
}

}
songrepository.class类

public class SongRepository {
private SongDAO songDAO;
private LiveData<List<SongEntity>> allSongs;

public SongRepository(Application application) {
    SongDatabase database = SongDatabase.getInstance(application);
    songDAO = database.songDAO();
    allSongs = songDAO.getAllSongs();
}

public void insert(SongEntity songEntity) {
    new InsertSongAsyncTask(songDAO).execute(songEntity);
}

public void update(SongEntity songEntity) {
    new UpdateSongAsyncTask(songDAO).execute(songEntity);
}

public void delete(SongEntity song) {
    new DeleteSongAsyncTask(songDAO).execute(song);
}

public void deleteAllSongs() {
    new DeleteAllSongsAsyncTask(songDAO).execute();
}

public LiveData<List<SongEntity>> getAllSongs() {
    return allSongs;
}

private static class InsertSongAsyncTask extends AsyncTask<SongEntity, Void, Void> {
    private SongDAO songDAO;

    private InsertSongAsyncTask(SongDAO songDAO) {
        this.songDAO = songDAO;
    }

    @Override
    protected Void doInBackground(SongEntity... songs) {
        songDAO.insert(songs[0]);
        return null;
    }
}

private static class UpdateSongAsyncTask extends AsyncTask<SongEntity, Void, Void> {
    private SongDAO songDAO;

    private UpdateSongAsyncTask(SongDAO songDAO) {
        this.songDAO = songDAO;
    }

    @Override
    protected Void doInBackground(SongEntity... songs) {
        songDAO.update(songs[0]);
        return null;
    }
}

private static class DeleteSongAsyncTask extends AsyncTask<SongEntity, Void, Void> {
    private SongDAO songDAO;

    private DeleteSongAsyncTask(SongDAO songDAO) {
        this.songDAO = songDAO;
    }

    @Override
    protected Void doInBackground(SongEntity... songs) {
        songDAO.delete(songs[0]);
        return null;
    }
}

private static class DeleteAllSongsAsyncTask extends AsyncTask<Void, Void, Void> {
    private SongDAO songDAO;

    private DeleteAllSongsAsyncTask(SongDAO songDAO) {
        this.songDAO = songDAO;
    }

    @Override
    protected Void doInBackground(Void... voids) {
        songDAO.deleteAll();
        return null;
    }
}

}
以及songviewmodel.class

public class SongViewModel extends AndroidViewModel {

private SongRepository repository;
private LiveData<List<SongEntity>> allSongs;

public SongViewModel(@NonNull Application application) {
    super(application);
    repository = new SongRepository(application);
    allSongs = repository.getAllSongs();
}

public void insert(SongEntity songEntity) {
    repository.insert(songEntity);
}

public void update(SongEntity songEntity) {
    repository.update(songEntity);
}

public void delete(SongEntity songEntity) {
    repository.delete(songEntity);
}

public void deleteAllSongs() {
    repository.deleteAllSongs();
}

public LiveData<List<SongEntity>> getAllSongs(){
    return allSongs;
}

}