RecyclerView Fold/Unfold implementations

FoldUnfold.java

public class FileWrapper {
  int type; // 0 : File, 1 : Directory
  int depth;  // 0~n
  File file;

  // contructor for injecting depedency, e.g. File object, type, depth
  // setters and getters
}

public class Adapter extends RecyclerView.Adapter<RecyclerView.Holder> {
  List<FileWrapper> dataset;
  SparseArray<Range> filePositonRangeInDirectory;

  // ... overriden methods

  // TODO need synchronized?
  public void fold(int position, List<FileWrapper> files) {
    final Range range = filePositonRangeInDirectory.get(position);
    filePositonRangeInDirectory.remove(position);
    final int start = range.getStart();
    for(int i = range.getEnd() i >= start; i--) {  // FIXME ArrayList.removeRange().
      dataset.remove(i);
    }
    notifyItemRangeRemoved(range.getStart(), range.getEnd());
  }

// TODO need synchronized?
  public void unfold(int position) {
    final int end = position + files.size() - 1;
    dataset.addAll(position, files);
    filePositonRangeInDirectory.append(position,
        Range.getRange(position, end);
    notifyItemRangeInserted(position, end);
  }


  public static class Range {
    int start;
    int end;

    private Range(int start, int end) {
      this.start = start;
      this.end = end;
    }

    public static final Range getRange(int start, int end) {
      return new Range(start, end);
    }

    // setters and getters
  }
}