41 lines
No EOL
1 KiB
JavaScript
41 lines
No EOL
1 KiB
JavaScript
// @flow
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import * as React from 'react';
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const speedOffset = 5;
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export default class AutoHideHandler {
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lastOffset: number;
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isHidden: boolean;
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listeners: Array<Function>;
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constructor(startHidden: boolean) {
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this.listeners = [];
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this.isHidden = startHidden;
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}
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addListener(listener: Function) {
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this.listeners.push(listener);
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}
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notifyListeners(shouldHide: boolean) {
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for (let i = 0; i < this.listeners.length; i++) {
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this.listeners[i](shouldHide);
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}
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}
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onScroll({nativeEvent}: Object) {
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const speed = nativeEvent.contentOffset.y < 0 ? 0 : this.lastOffset - nativeEvent.contentOffset.y;
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if (speed < -speedOffset && !this.isHidden) { // Go down
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this.notifyListeners(true);
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this.isHidden = true;
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} else if (speed > speedOffset && this.isHidden) { // Go up
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this.notifyListeners(false);
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this.isHidden = false;
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}
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this.lastOffset = nativeEvent.contentOffset.y;
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}
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} |