OnScrollEvent 继承自： Event['ScrollableControl']

Payload for on_scroll handlers.

属性

名称	类型	默认值	说明
event_type	ScrollType	required	Logical type of the scroll notification. Determines which optional fields are populated: - UPDATE: scroll_delta - USER: direction - OVERSCROLL: overscroll and velocity
pixels	float	required	Current scroll offset in logical pixels.
min_scroll_extent	float	required	Minimum in-range value for pixels. pixels may still be out_of_range during overscroll. For unbounded scrollables this value can be negative infinity.
max_scroll_extent	float	required	Maximum in-range value for pixels. pixels may still be out_of_range during overscroll. For unbounded scrollables this value can be positive infinity.
viewport_dimension	float	required	Visible viewport extent along the scroll axis, in logical pixels.
scroll_delta	Optional[float]	None	Delta in logical pixels since the previous update. Populated for UPDATE notifications.
direction	Optional[ScrollDirection]	None	User scroll direction reported by Flutter. Populated for USER notifications.
overscroll	Optional[float]	None	Logical pixels that were prevented from being applied to pixels. Negative values indicate overscroll on the start side; positive values indicate overscroll on the end side. Populated for OVERSCROLL.
velocity	Optional[float]	None	Scroll velocity when overscroll occurred, in logical pixels per second. Populated for OVERSCROLL.

只读属性

名称	类型	默认值	说明
out_of_range	bool	—	Whether pixels is outside scroll extents. Returns: True if pixels < min_scroll_extent or pixels > max_scroll_extent; otherwise False.
at_edge	bool	—	Whether pixels is exactly at either scroll edge. Returns: True when pixels equals min_scroll_extent or max_scroll_extent; otherwise False.
extent_before	float	—	Quantity of content conceptually "before" the viewport. This corresponds to the content preceding the visible region in the current scroll direction.
extent_after	float	—	Quantity of content conceptually "after" the viewport. This corresponds to the content following the visible region in the current scroll direction.
extent_total	float	—	Total conceptual content extent available to the scrollable. Equivalent to: max_scroll_extent - min_scroll_extent + viewport_dimension.