onVisibilityChanged method

Implementation

void onVisibilityChanged(VisibilityInfo info) {
  if (oldVisibility == (info.visibleFraction * 100)) return;

  visibleHeight = info.size.height > 0
      ? ((info.visibleBounds.height / info.size.height) * 100)
      : 0.0;
  visibleWidth = info.size.width > 0
      ? ((info.visibleBounds.width / info.size.width) * 100)
      : 0.0;
  visibleArea = info.visibleFraction * 100;

  oldVisibility = visibleArea ?? 0.0;

  if (visibleArea! > 1 && !hasGoneOnscreen) {
    if (!isNullOrEmpty(_onscreen)) EventHandler(this).execute(_onscreen);
    hasGoneOnscreen = true;
  } else if (visibleArea! == 0 && hasGoneOnscreen) {
    if (!isNullOrEmpty(_offscreen)) EventHandler(this).execute(_offscreen);
    hasGoneOnscreen = false;
  }
}