onScroll method

void onScroll(ScrollMetrics metrics)

Implementation

void onScroll(ScrollMetrics metrics){
  final newAtBottom = metrics.pixels >= metrics.maxScrollExtent && !metrics.outOfRange;
  final newAtTop = metrics.pixels <= metrics.minScrollExtent && metrics.outOfRange;

  if(widget.shaderType != null && widget.shaderType != NUIShaderMaskType.NONE && (newAtBottom != atBottom || newAtTop != atTop)) {
    //Scroll position changed
    atBottom = newAtBottom;
    atTop = newAtTop;

    bool shouldFadeTop = false;
    bool shouldFadeBottom = false;
    if (widget.shaderType == NUIShaderMaskType.TOP_BOTTOM_FADE) {
      shouldFadeTop = !atTop;
      shouldFadeBottom = !atBottom;
    }
    else if (widget.shaderType == NUIShaderMaskType.BOTTOM_FADE) {
      shouldFadeBottom = !atBottom;
    }
    else if (widget.shaderType == NUIShaderMaskType.TOP_FADE) {
      shouldFadeTop = !atTop;
    }

    if (shouldFadeTop && shouldFadeBottom)
      toUseShade = NUIShaderMaskType.TOP_BOTTOM_FADE;
    else if (shouldFadeTop)
      toUseShade = NUIShaderMaskType.TOP_FADE;
    else if (shouldFadeBottom)
      toUseShade = NUIShaderMaskType.BOTTOM_FADE;
    else
      toUseShade = NUIShaderMaskType.NONE;

    updateNUIState(id: instanceId, update: items);
  }

  if ((metrics.maxScrollExtent - (widget.paginateMargin ?? 0)) <= metrics.pixels) {
    onPaginationLoad(isFirst: false, cursor: curModel.cursor);
  }
  additionalScrollListener(metrics);

  if(widget.scrollListener != null){
    widget.scrollListener!(metrics.pixels, atTop, atBottom);
  }
}