如何从内部存储器访问设备歌曲

Question

我是Android开发的新手，我想从我的应用程序打开内部内存。但它在除三星设备之外的所有设备上都是开放的。它在摩托罗拉设备，其他手机和模拟器中也很好用。我在这里得到null：if (scanFolder == null) {return null;}

 public List<Folder> loadInBackground() {
        List<Folder> folderList = new ArrayList<>();
        List<Song> songList = new ArrayList<>();
        // Permission Check Runtime For M and above
        if (PermissionChecker.checkCallingOrSelfPermission(getContext(), Manifest.permission.READ_EXTERNAL_STORAGE) == PermissionChecker.PERMISSION_GRANTED) {
            FileExtensionFilter mFileExtensionFilter = new FileExtensionFilter(Constants.fileExtensions);
            if (dir != null) {
                File[] scanFolder = dir.listFiles(mFileExtensionFilter);

                // Getting Null over here in Samsung Device scanFolder getting null
                if (scanFolder == null) {
                    return null;
                }
                // Get Folder List
                for (File aScanFolder : scanFolder) {
                    Folder folder = new Folder();
                    Cursor cursor = getContext().getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, new String[]{MediaStore.Audio.Media.DATA}, MediaStore.Audio.Media.DATA + " like ? ", new String[]{"%" + aScanFolder.getAbsolutePath() + "%"}, null);
                    if (cursor != null) {
                        int count = cursor.getCount();
                        if (count != 0) {
                            if (!aScanFolder.isDirectory()) {
                                String path = aScanFolder.getAbsolutePath();
                                Song song = Helper.getSongData(Extras.getInstance().getSongSortOrder(), getContext(), path);
                                songList.add(song);
                            }
                            if (!aScanFolder.getAbsolutePath().startsWith("/d")) {
                                Log.e("FolderLoader", "Path --> " + aScanFolder.getAbsolutePath());
                                folder.setFile(aScanFolder);
                                folder.setFileCount(count);
                                folder.setSongList(songList);
                                folderList.add(folder);
                            }
                        }
                    }
                    if (cursor != null) {
                        cursor.close();
                    }
                }
                Collections.sort(folderList, new Comparator<Folder>() {
                    @Override
                    public int compare(Folder f1, Folder f2) {
                        if ((f1.getFile().isDirectory() && f2.getFile().isDirectory()))
                            return f1.getFile().getName().compareToIgnoreCase(f2.getFile().getName());
                        else if (f1.getFile().isDirectory() && !f2.getFile().isDirectory())
                            return -1;
                        else if (!f1.getFile().isDirectory() && f2.getFile().isDirectory())
                            return 1;
                        else if (!f1.getFile().isDirectory() && !f2.getFile().isDirectory())
                            return f1.getFile().getName().compareToIgnoreCase(f2.getFile().getName());
                        else return 0;
                    }

                });
                if (!dir.getAbsolutePath().equals("/")) {
                    Folder folder = new Folder();
                    if (dir.getParentFile() != null) {
                        folder.setFile(dir.getParentFile());
                        Log.e("FolderLoader", dir.getParentFile().getAbsolutePath());
                        folderList.add(0, folder);
                    }
                }
            }

            return folderList;
        } else {
            // Error Message
            Log.d("Folder", "Permission not granted");
            return Collections.emptyList();
        }
    } 

我在三星设备中获得此屏幕UI。

Getting All songs in Other device except Samsung Device