import "../css/Leftrightlinkage.less";
import React, { Component } from "react";
 
export default class Leftrightlinkage extends Component {
  constructor(...args) {
    super(...args);
    this.state = {
      list: [
        { id: 1, title: "列表1" },
        { id: 2, title: "列表2" },
        { id: 3, title: "列表3" },
        { id: 4, title: "列表4" },
        { id: 5, title: "列表5" },
        { id: 6, title: "列表6" },
        { id: 7, title: "列表7" },
        { id: 8, title: "列表8" },
        { id: 9, title: "列表9" },
        { id: 10, title: "列表10" },
      ],
      LeftList: [
        { id: 1, title: "列表1", height: 600 },
        { id: 2, title: "列表2", height: 600 },
        { id: 3, title: "列表3", height: 600 },
        { id: 4, title: "列表4", height: 600 },
        { id: 5, title: "列表5", height: 600 },
        { id: 6, title: "列表6", height: 600 },
        { id: 7, title: "列表7", height: 600 },
        { id: 8, title: "列表8", height: 600 },
        { id: 9, title: "列表9", height: 600 },
        { id: 10, title: "列表10", height: 600 },
      ],
      curr: 0, //存储下标
    };
 
    // 默认添加一个 因为第一个的scrollTop值是0
    this.LeftHeight = [0];
    // 滚动的开关
    this.Swich = true;
  }
 
  // 渲染完成获取每一个列表距离顶部的距离
  componentDidMount() {
    // 定义为0 每次就可以循环加起来就是盒子距离顶部的距离
    this.Height = 0;
    // 循环获取每一个的高
    for (var i = 0; i < this.state.LeftList.length - 1; i++) {
      this.Height += this.state.LeftList[i].height;
      this.LeftHeight.push(this.Height);
    }
  }
  //   点击左侧列表 点击获取下标
  FnTable(index) {
    // 点击的时候让右边的滚动事件为false
    this.Swich = false;
    // 存储下标
    this.setState({
      curr: index,
    });
    // 根据下标取出数组中对应下标的scrollTop值  就让右边的scrollTop为数组中取出的值
    this.refs["leftItem"].scrollTop = this.LeftHeight[index];
  }
  FnScroll() {
    // 监听滚动
    this.scrollTop = this.refs["leftItem"].scrollTop;
 
    // 这边用开关判断是否执行
    if (this.Swich) {
      // 存放下标
      let num = 0;
      // 循环取出数组中的数值
      for (var i = 0; i < this.LeftHeight.length - 1; i++) {
        if (this.scrollTop >= this.LeftHeight[i]) {
          num = i;
        }
      }
      // 存储下标
      this.setState({
        curr: num,
      });
    }
    // 判断滚动的值和数组中的值相等 开关为true
    if (this.scrollTop == this.LeftHeight[this.state.curr]) {
      setTimeout(() => {
        this.Swich = true;
      });
    }
  }
 
  render() {
    return (
      <div className="box">
        <div className="scroll">
          <div className="list-left">
            {this.state.list.map((item, index) => (
              <div
                className="left-item"
                ref="scrollLeft"
                className={this.state.curr === index ? "active" : "left-item"}
                key={item.id}
                onClick={this.FnTable.bind(this, index)}
              >
                {item.title}
              </div>
            ))}
          </div>
          <div
            className="list-right"
            ref="leftItem"
            onScroll={this.FnScroll.bind(this)}
          >
            {this.state.LeftList.map((item) => (
              <div
                className="right-item"
                key={item.id}
                style={{ height: item.height }}
              >
                <div className="item-title">{item.title}</div>
              </div>
            ))}
          </div>
        </div>
      </div>
    );
  }
}

 .box {
     width: 100vw;
     height: 100vh;
 
     .scroll {
         width: 100vw;
         height: 100vh;
         display: flex;
 
         .list-left {
             width: 200px;
             height: 100vh;
             background: rgb(151, 151, 151);
 
             .left-item {
                 height: 120px;
                 text-align: center;
                 line-height: 120px;
                 color: #ffffff;
                 font-size: 36px;
                 border: 3px solid #ffffff;
                 box-sizing: border-box;
             }
 
             .active {
                 height: 120px;
                 text-align: center;
                 line-height: 120px;
                 color: #ffffff;
                 font-size: 36px;
                 border: 3px solid #ffffff;
                 background-color: #f100d9;
                 box-sizing: border-box;
             }
         }
 
         .list-right {
             width: 100vw;
             height: 100vh;
             background-color: #15ff00;
             overflow: scroll;
 
             .right-item {
                 height: 400px;
                 border: 5px solid #0040ff;
                 font-size: 40px;
                 color: #ffffff;
                 box-sizing: border-box;
             }
         }
     }
 
 }