Package com.vaadin.client

Class ScrollPositionHandler

  • public class ScrollPositionHandler
extends Object
    Handler for restoring scroll position when user navigates back / forward inside the application. This is used instead of browser's native history.scrollRestoration = "auto" since it won't work with content generated by JavaScript.

    Uses History.state to store history indexes and a token. This is done because need to know which index in the scroll position arrays does each history entry map to. The token used to identify the correct scroll positions array.

    Uses window.sessionStorage to store the actual scroll position arrays. This is used so that the scroll positions can be always restored, even when navigating from outside back into a middle of the history chain. The arrays are stored using the token so that they can be linked to a specific history index.

    Since:
    1.0
    Author:
    Vaadin Ltd

    • Constructor Detail

      • ScrollPositionHandler

        public ScrollPositionHandler​(Registry registry)
        Creates a new instance connected to the given registry.
        Parameters:
        registry - the global registry

      • ScrollPositionHandler

        protected ScrollPositionHandler()
        Default constructor to use in subclasses to override all functionality from this class.

    • Method Detail

      • onPopStateEvent

        public void onPopStateEvent​(elemental.events.PopStateEvent event,
                            boolean triggersServerSideRoundtrip)
        Store scroll positions and restore scroll positions depending on the given pop state event.

        This method behaves differently if there has been a beforeClientNavigation(String) before this, and if the pop state event is caused by a fragment change that doesn't require a server side round-trip.

        Parameters:
        event - the pop state event
        triggersServerSideRoundtrip - true if the pop state event triggers a server side request, false if not

      • setIgnoreScrollRestorationOnNextPopStateEvent

        public void setIgnoreScrollRestorationOnNextPopStateEvent​(boolean ignoreScrollRestorationOnNextPopStateEvent)
        Tells this scroll handler that the next call to onPopStateEvent(PopStateEvent, boolean) should not try to restore scroll position.

        There are differences between browsers on which order the pop state and fragment change events are fired. This is just to recognize the case where a fragment change event fired by framework (to get scroll to fragment) causes a pop state event that should be ignored here.

        Parameters:
        ignoreScrollRestorationOnNextPopStateEvent - true to NOT restore scroll on pop state event, false to restore

      • beforeClientNavigation

        public void beforeClientNavigation​(String newHref)
        Store scroll positions when there has been navigation triggered by a click on a link element and no server round-trip is needed. It means navigating within the same page.

        If href for the page navigated into contains a hash (even just #), then the browser will fire a pop state event afterwards.

        Parameters:
        newHref - the href of the clicked link

      • afterServerNavigation

        public void afterServerNavigation​(elemental.json.JsonObject state)
        Store scroll positions when there has been navigation triggered by a click on a link element and a server round-trip was needed. This method is called after server-side part is done.
        Parameters:
        state - includes scroll position of the previous page and the complete href of the router link that was clicked and caused this navigation

      • getScrollPosition

        public static double[] getScrollPosition()
        Gets the scroll position of the page as an array.
        Returns:
        an array containing scroll position x (left) and y (top) in order