android-studio - 我正在制作音乐播放器，我想让应用程序读取存储空间以获取歌曲

Question

我已经在 Manifest 中给出了 READ_EXTERNAL_STORAGE，但应用程序仍然无法读取存储空间并在列表视图中显示歌曲。我在 xml 中添加了一个列表视图。我不知道问题出在代码还是设备上。我对android工作室很陌生。请帮忙

public class MainActivity extends AppCompatActivity {

    private ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {


        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = findViewById(R.id.listView);
        Dexter.withContext(this)
                .withPermission(Manifest.permission.READ_EXTERNAL_STORAGE)
                .withListener(new PermissionListener() {
                    @Override
                    public void onPermissionGranted(PermissionGrantedResponse permissionGrantedResponse) {

//                        Toast.makeText(MainActivity.this, "Runtime permission given", Toast.LENGTH_SHORT).show();

                       display();



                    }

                    @Override
                    public void onPermissionDenied(PermissionDeniedResponse permissionDeniedResponse) {

                    }

                    @Override
                    public void onPermissionRationaleShouldBeShown(PermissionRequest permissionRequest, PermissionToken permissionToken) {
                        permissionToken.continuePermissionRequest();
                    }
                })
                .check();
    }

    public ArrayList<File> fetchSongs(File file){
        ArrayList<File> arrayList = new ArrayList<>();
        File [] songs = file.listFiles();
        if(songs !=null){
            for(File myFile: songs){
                if(!myFile.isHidden() && myFile.isDirectory()){
                    arrayList.addAll(fetchSongs(myFile));
                }
                else{
                    if(myFile.getName().endsWith(".mp3") && !myFile.getName().startsWith(".")){
                        arrayList.add(myFile);
                    }
                }
            }
        }
        return arrayList;
    }

    void display(){
        ArrayList<File> mySongs = fetchSongs(Environment.getExternalStorageDirectory());
        String[] items = new String[mySongs.size()];
        for(int i=0;i<mySongs.size();i++){
            items[i] = mySongs.get(i).getName().replace(".mp3", "");
        }
          ArrayAdapter<String> ad = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1,items);
        listView.setAdapter(ad);

    }
}

标签： android-studiolistviewandroid-music-player