public static List<String> getSystemPhotoList(Context context)
    {
        List<String> result = new ArrayList<String>();
        Uri uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
        
        ContentResolver contentResolver = context.getContentResolver();
        Cursor cursor = contentResolver.query(uri, null, null, null, null);
        if (cursor == null || cursor.getCount() <= 0) return null; // 没有图片
        while (cursor.moveToNext())
        {
            int index = cursor
                    .getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
            String path = cursor.getString(index); // 文件地址
            File file = new File(path);
            if (file.exists())
            {
                result.add(path);
                Log.i(TAG, path);
            }
        }
        
        return result ;
    }