文件listfiles（）返回Null

Question

listFiles（）返回null，但是在该目录中有可用文件时，我还请求了Runtime中的READ_EXTERNAL_STORAGE权限，仍然面临相同的问题。我的SDK版本29

@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    recyclerView = findViewById(R.id.recyclerView);
    layoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(layoutManager);

    if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
            == PackageManager.PERMISSION_GRANTED){
        File file = new File(Environment.getExternalStorageDirectory().toString() + WHATSAPP_DIR_LOCATION);

        Log.d("LOL",String.valueOf(file));

        MyAdapter recyclerAdapter = new MyAdapter(this.getListFiles(file),MainActivity.this);
        recyclerView.setAdapter(recyclerAdapter);
    }
    else {
        ActivityCompat.requestPermissions(this,new String[]{
                Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE
        },REQUEST_CODE);
    }

 private ArrayList<File> getListFiles(File parentDir){

    ArrayList<File> inFiles = new ArrayList<>();
    File[] files;

    files = parentDir.listFiles();
    Log.d("Test1","hey");

    if (files != null){

        Log.d("Test2","hey");
        for (File file: files){
            if (file.getName().endsWith(".jpg") || file.getName().endsWith(".gif") || file.getName().endsWith(".mp4")){

                if (!inFiles.contains(file))
                    inFiles.add(file);
            }
        }
    }
    return inFiles;
}