forked from vergnet/application-amicale
85 lines
2.4 KiB
JavaScript
85 lines
2.4 KiB
JavaScript
// @flow
|
|
|
|
const speedOffset = 5;
|
|
|
|
type ListenerFunctionType = (shouldHide: boolean) => void;
|
|
|
|
export type OnScrollType = {
|
|
nativeEvent: {
|
|
contentInset: {bottom: number, left: number, right: number, top: number},
|
|
contentOffset: {x: number, y: number},
|
|
contentSize: {height: number, width: number},
|
|
layoutMeasurement: {height: number, width: number},
|
|
zoomScale: number,
|
|
},
|
|
};
|
|
|
|
/**
|
|
* Class used to detect when to show or hide a component based on scrolling
|
|
*/
|
|
export default class AutoHideHandler {
|
|
lastOffset: number;
|
|
|
|
isHidden: boolean;
|
|
|
|
listeners: Array<ListenerFunctionType>;
|
|
|
|
constructor(startHidden: boolean) {
|
|
this.listeners = [];
|
|
this.isHidden = startHidden;
|
|
}
|
|
|
|
/**
|
|
* Adds a listener to the hide event
|
|
*
|
|
* @param listener
|
|
*/
|
|
addListener(listener: (shouldHide: boolean) => void) {
|
|
this.listeners.push(listener);
|
|
}
|
|
|
|
/**
|
|
* Notifies every listener whether they should hide or show.
|
|
*
|
|
* @param shouldHide
|
|
*/
|
|
notifyListeners(shouldHide: boolean) {
|
|
this.listeners.forEach((func: ListenerFunctionType) => {
|
|
func(shouldHide);
|
|
});
|
|
}
|
|
|
|
/**
|
|
* Callback to be used on the onScroll animated component event.
|
|
*
|
|
* Detects if the current speed exceeds a threshold and notifies listeners to hide or show.
|
|
*
|
|
* The hide even is triggered when the user scrolls down, and the show event on scroll up.
|
|
* This does not take into account the speed when the y coordinate is negative, to prevent hiding on over scroll.
|
|
* (When scrolling up and hitting the top on ios for example)
|
|
*
|
|
* //TODO Known issue:
|
|
* When refreshing a list with the pull down gesture on ios,
|
|
* this can trigger the hide event as it scrolls down the list to show the refresh indicator.
|
|
* Android shows the refresh indicator on top of the list so this is not an issue.
|
|
*
|
|
* @param event The scroll event generated by the animated component onScroll prop
|
|
*/
|
|
onScroll(event: OnScrollType) {
|
|
const {nativeEvent} = event;
|
|
const speed =
|
|
nativeEvent.contentOffset.y < 0
|
|
? 0
|
|
: this.lastOffset - nativeEvent.contentOffset.y;
|
|
if (speed < -speedOffset && !this.isHidden) {
|
|
// Go down
|
|
this.notifyListeners(true);
|
|
this.isHidden = true;
|
|
} else if (speed > speedOffset && this.isHidden) {
|
|
// Go up
|
|
this.notifyListeners(false);
|
|
this.isHidden = false;
|
|
}
|
|
this.lastOffset = nativeEvent.contentOffset.y;
|
|
}
|
|
}
|