Question

滚动功能无法正常工作。当我上下滚动时没有添加类。我未能触发添加类onscroll函数。因此，如何添加类onscroll函数。请建议我如何在滚动条上添加/删除课程。

 import React, { Component } from 'react';
    import './App.css';
    import About from './About';
    import Contact from './Contact';
    import {SectionsContainer, Section, Header, Footer} from 'react-fullpage';

    class App extends Component {
      state = {
        isTop: true,
      };

      componentWillMount() {
        var scrollpos = window.scrollY;
    var header = document.querySelector("custom-section");

    function add_class_on_scroll() {
        header.classList.add("home-section--active");
    }

    function remove_class_on_scroll() {
        header.classList.remove("home-section--active");
    }

    window.addEventListener('scroll', function(){ 
        //Here you forgot to update the value
        scrollpos = window.scrollY;

        if(scrollpos > 10){
            add_class_on_scroll();
        }
        else {
            remove_class_on_scroll();
        }
    });
      }
      render() {


        let options = {
          sectionClassName:     'section',
          anchors:              ['sectionOne', 'sectionTwo', 'sectionThree'],
          scrollBar:            false,
          navigation:           false,
          verticalAlign:        false,
          sectionPaddingTop:    '0px',
          sectionPaddingBottom: '0px',
          arrowNavigation:      false
        };
        return (
          <div className="App">
          <SectionsContainer className="container" {...options}>
          <Section className="custom-section home-section" verticalAlign="true"><About/></Section>
          <Section className="custom-section home-section"><Contact /></Section>
        </SectionsContainer>
          </div>
        );
      }
    }

    export default App;

Answer 1

您应该将滚动处理逻辑放在componentdidmount生命周期内，因为在安装组件之后，您可以访问DOM元素。

componentDidMount() {
        var scrollpos = window.scrollY;
    var header = document.querySelector("custom-section");

    function add_class_on_scroll() {
        header.classList.add("home-section--active");
    }

    function remove_class_on_scroll() {
        header.classList.remove("home-section--active");
    }

    window.addEventListener('scroll', function(){ 
        //Here you forgot to update the value
        scrollpos = window.scrollY;

        if(scrollpos > 10){
            add_class_on_scroll();
        }
        else {
            remove_class_on_scroll();
        }
    });
      }

我该如何在滚动中添加或删除类？

1 个答案: