private void parseSelectedMedias(Bundle savedInstanceState, Intent intent) {
        if (savedInstanceState != null) {
            mSelectedImages = savedInstanceState.getParcelableArrayList(Boxing.EXTRA_SELECTED_MEDIA);
            mAlbumId = savedInstanceState.getString(Boxing.EXTRA_ALBUM_ID);
            mStartPos = savedInstanceState.getInt(Boxing.EXTRA_START_POS, 0);
        } else if (intent != null) {
            mStartPos = intent.getIntExtra(Boxing.EXTRA_START_POS, 0);
            mSelectedImages = intent.getParcelableArrayListExtra(Boxing.EXTRA_SELECTED_MEDIA);
            mAlbumId = intent.getStringExtra(Boxing.EXTRA_ALBUM_ID);
        }
    }
to clear all medias the first time(the page number is 0). do some clean work.
boxing/src/main/java/com/bilibili/boxing/AbsBoxingViewActivity.java