这是我第一次真正在项目中正确使用React Hooks之一,所以如果我不在那儿请多多包涵。
在下面的组件中,我的目标是在加载时显示<HelperTooltip>
,并且当滚动div(而非窗口)滚动时,在滚动X像素后我想隐藏。
我的思维过程是在滚动的<div/>
元素上创建一个useRef对象,然后可以使用回调函数添加事件侦听,然后该回调函数可以切换状态以隐藏<HelperTooltip>
>
我在下面创建了一个Codesandbox来尝试演示我正在尝试做的事情。如您在演示中所看到的,node.addEventListener('click')
正常工作,但是当我尝试调用node.addEventListener('scroll')
时却没有触发。
我不确定是否采用错误的方法,将不胜感激。在codesandbox演示中,它是我试图在滚动中隐藏的反应图像,而不是<HelperTooltip>
CodeSandbox链接:https://codesandbox.io/s/zxj322ln24
import React, { useRef, useCallback, useState } from "react";
import ReactDOM from "react-dom";
import "./styles.css";
const App = props => {
const [isLogoActive, toggleLogo] = useState(true);
const scrollElementRef = useCallback(node => {
node.addEventListener("click", event => {
console.log("clicked", event);
});
/*
I want to add the scroll event listener
here and the set the state isLogoActive to
false like the event listener above but the 'scroll' event
is firing --- see below on line 21
*/
// node.addEventListener("scroll", event => {
// console.log("scrolled", event);
// toggle log
// });
});
return (
<div className="scrolling-container">
<div ref={scrollElementRef} className="scrolling-element">
<p>top</p>
{isLogoActive && (
<div className="element-to-hide-after-scroll">
<img
style={{ width: "100px", height: "100px" }}
src="https://arcweb.co/wp-content/uploads/2016/10/react-logo-1000-transparent-768x768.png"
/>
</div>
)}
<p>bottom</p>
</div>
</div>
);
};
ReactDOM.render(<App />, document.getElementById("app"));
答案 0 :(得分:2)
对此特定用例更简单的方法可能是使用scrollTop
道具并使用事件target
中的const { useState } = React;
const App = props => {
const [isLogoActive, setLogoActive] = useState(true);
const onScroll = e => {
setLogoActive(e.target.scrollTop < 100);
};
return (
<div onScroll={onScroll} style={{ height: 300, overflowY: "scroll" }}>
<p style={{ marginBottom: 200 }}>top</p>
<img
style={{
width: 100,
height: 100,
visibility: isLogoActive ? "visible" : "hidden"
}}
src="https://arcweb.co/wp-content/uploads/2016/10/react-logo-1000-transparent-768x768.png"
/>
<p style={{ marginTop: 200 }}>bottom</p>
</div>
);
};
ReactDOM.render(<App />, document.getElementById("root"));
属性来确定是否应该隐藏图像
示例
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<div id="root"></div>
<button class="btn btn-primary follow">
<span class="fa fa-user-plus text-muted"></span>
</button>
答案 1 :(得分:2)
根据您的使用情况,限制滚动事件侦听器通常也很好,这样它们就不会在每次像素更改时都运行。
const App = props => {
const [isLogoActive, setLogoActive] = useState(true);
const onScroll = useMemo(() => {
const throttled = throttle(e => setLogoActive(e.target.scrollTop < 100), 300);
return e => {
e.persist();
return throttled(e);
};
}, []);
return (
<div onScroll={onScroll}>
<img
style={{ visibility: isLogoActive ? 'visible' : 'hidden' }}
src="https://arcweb.co/wp-content/uploads/2016/10/react-logo-1000-transparent-768x768.png"
/>
</div>
);
};
lodash中提供了throttle
功能。
答案 2 :(得分:0)
在您的示例中,滚动不是在scrolling-element
上触发的,而是在scrolling-container
上触发的,因此您想在此放置引用:https://codesandbox.io/s/ko4vm93moo:)
但是正如Throlle所说,您也可以使用onScroll道具!
答案 3 :(得分:0)
这是使用useRef()在div上绑定addEventListener的正确方法
import React, { useState, useEffect, useCallback, useRef } from 'react';
function ScrollingWrapper(props) {
const [hasScrolledDiv, setScrolled] = useState(false);
const scrollContainer = useRef(null);
const onScroll = useCallback((event) => {
if(event.target.scrollTop > 125){
setScrolled(true);
} else if(event.target.scrollTop < 125) {
setScrolled(false);
}
}, []);
useEffect(() => {
scrollContainerWrapper.current.addEventListener('scroll', onScroll);
return () => scrollContainerWrapper.current.removeEventListener('scroll', onScroll);
},[]);
return (
<div ref={scrollContainerWrapper}>
{props.children}
</div>
);
}
export default ScrollingWrapper;