如何将原始文件夹中的所有mp3文件按名称和其他元数据放入列表中？

Question

I'm developing an app that can play MP3 files. I want to convert mp3 files inside the raw folder into an ArrayList of song objects, using the mp3 file's name as its title. Here's my code. I've taken it from this question's answer but it doesn't seem to work for me.

public void getSongList() {
    try {
        Log.d("Test", "reached");
        Field[] fields = R.raw.class.getDeclaredFields();

        Log.d("Test", "reached2");
        for (Field f : fields) {
            allSongs.addSong(new Song(0, f.getName(), ""));
        }
        Log.d("Test", "reached3");
    } catch (Exception e) {
        Log.d("Test", "reached4");
        Log.d("Test", allSongs.getSongs().size() + "");
        Log.d("Test", e.toString());
        return;
    }
}

Here are the logs:

07-03 15:50:52.497 17106-17106/poc.cevt.hmi.com.musicplayerapp D/Test: reached
07-03 15:50:52.497 17106-17106/poc.cevt.hmi.com.musicplayerapp D/Test: reached2
07-03 15:50:52.498 17106-17106/poc.cevt.hmi.com.musicplayerapp D/Test: reached4
07-03 15:50:52.498 17106-17106/poc.cevt.hmi.com.musicplayerapp D/Test: 0
07-03 15:50:52.498 17106-17106/poc.cevt.hmi.com.musicplayerapp D/Test: java.lang.NullPointerException: Attempt to invoke virtual method 'void poc.cevt.hmi.com.musicplayerapp.AllSongs.addSong(poc.cevt.hmi.com.musicplayerapp.Song)' on a null object reference

I have one mp3 file inside my raw folder. The Song's first and third parameters are ID and artist respectively, I'm just trying to get the title to work for now. Any alternative/better solutions to what I have are also welcome.

Answer 1

allSongs为null ，因此您在调用addSong()收到NullPointerException 。