class UIScrollViewtype

type UIScrollView​.ScrollEventData

The data structure contained by each UIScrollView.ScrollEvent.

type ScrollEventData = {
  yOffset: number;
  xOffset: number;
  horizontalVelocity: number;
  verticalVelocity: number;
  scrolledDown?: boolean;
  scrolledUp?: boolean;
  scrolledHorizontalStart?: boolean;
  scrolledHorizontalEnd?: boolean;
  atTop?: boolean;
  atBottom?: boolean;
  atHorizontalStart?: boolean;
  atHorizontalEnd?: boolean;
};

Notes

• The platform dependent offsets xOffset and yOffset can be saved and restored later using UIScrollView.scrollTo(). These should not be used for any other purpose.
• The horizontalVelocity and verticalVelocity (a number representing the approximate screen widths/heights per second), and scrolledUp, scrolledDown, scrolledHorizontalStart, scrolledHorizontalEnd (booleans) values are platform independent and represent the last scroll movement.
• The boolean values of atTop, atBottom, atHorizontalStart, and atHorizontalEnd represent the current position. These are affected by the threshold values set on the UIScrollView instance itself — e.g. with a top threshold of 5 pixels, the atTop value remains true while the container is scrolled within 0-5 pixels from the top of its content.

Instance members

• yOffset
  Vertical scroll offset; platform-dependent value, should not be used for positioning but can be used with UIScrollContainer.scrollTo().
• xOffset
  Horizontal scroll offset; platform-dependent value, may change with text direction, should not be used for positioning but can be used with UIScrollContainer.scrollTo().
• horizontalVelocity
  Horizontal scrolling velocity (screen widths per second).
• verticalVelocity
  Horizontal scrolling velocity (screen heights per second).
• scrolledDown
  True if (last) scrolled down.
• scrolledUp
  True if (last) scrolled up.
• scrolledHorizontalStart
  True if (last) scrolled left for LTR text direction, right for RTL.
• scrolledHorizontalEnd
  True if (last) scrolled right for LTR text direction, left for RTL.
• atTop
  True if the scroll container is scrolled to the top.
• atBottom
  True if the scroll container is scrolled to the bottom.
• atHorizontalStart
  True if the scroll container is scrolled to the left for LTR text direction, right for RTL.
• atHorizontalEnd
  True if the scroll container is scrolled to the right for LTR text direction, left for RTL.

Related

• class UIScrollView
  A view class that represents a container element that allows users to scroll, emitting asynchronous scroll events.