react中實現可拖動div

把拖動div功能用react封裝成class，在頁面直接引入該class即可使用。

title為可拖動區域。panel為要實現拖動的容器。

優化了拖動框超出頁面範圍的情況，也優化了拖動太快時滑鼠超出可拖動區域的情況，優化了拖動會卡頓的情況。

頁面中添加引入方法：

<Draggable panelId="要拖動容器的id" titleId="容器內標題的id" contentId="容器內除標題外的其他部分id" setPanelPosition={this.setPanelPosition.bind(this)}/>

頁面中添加拖拽回調函數

  //推拽回調函數
  setPanelPosition(left,top){
    this.setState({pageX: left, pageY: top})
  }

要拖動的div如下：

<div id="要拖動的id" style={{left:this.state.pageX,top:this.state.pageY}}></div>

封裝的class代碼：

import React from 'react';
class Draggable extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
    };
  }
  //拖拽
  initDrag(){
    let {panelId,titleId,contentId} = this.props;
    this.panelDom = document.getElementById(panelId);
    this.titleDom = document.getElementById(titleId);
    this.contentDom = document.getElementById(contentId);
    this.backgroundDom = document.body;
    this.bindEvent();
  }

  //region event
  componentDidMount() {
    this.initDrag();
  }
  bindEvent(){
    this.titleDom.onmousedown = this.onMouseDown.bind(this);
    this.titleDom.onmouseup = this.onMouseUp.bind(this);
    this.titleDom.onmousemove = this.onMouseMove.bind(this);

    this.contentDom.onmouseup = this.onContentMouseUp.bind(this);
    this.contentDom.onmousemove = this.onContentMouseMove.bind(this);

    this.backgroundDom.onmouseup = this.onBackgroundMouseUp.bind(this);
    this.backgroundDom.onmousemove = this.onBackgroundMouseMove.bind(this);
    let step = ()=>{
      this.activeAnimation = true;
      window.requestAnimationFrame(step);
    };
    window.requestAnimationFrame(step);
  }

  /**
   * 滑鼠按下，設置modal狀態為可移動，並註冊滑鼠移動事件
   * 計算滑鼠按下時，指針所在位置與modal位置以及兩者的差值
   **/
  onMouseDown (e) {
    const position = this.getPosition(e)
    this.setState({moving: true, diffX: position.diffX, diffY: position.diffY})
  }

  // 鬆開滑鼠，設置modal狀態為不可移動
  onMouseUp (e) {
    const { moving } = this.state
    moving && this.setState({moving: false});
  }

  // 滑鼠移動重新設置modal的位置
  onMouseMove (e) {
    const {moving, diffX, diffY} = this.state
    if (moving) {
      if(this.activeAnimation){
        // 獲取滑鼠位置數據
        const position = this.getPosition(e)
        // 計算modal應該隨滑鼠移動到的坐標
        const x = position.mouseX - diffX
        const y = position.mouseY - diffY
        // 視窗大小，結構限制，需要做調整，減去側邊欄寬度
        const { clientWidth, clientHeight } = document.documentElement
        const modal = this.panelDom
        if (modal) {
          // 計算modal坐標的最大值
          const maxHeight = clientHeight - modal.offsetHeight
          const maxWidth = clientWidth - modal.offsetWidth
          // 判斷得出modal的最終位置，不得超出瀏覽器可見視窗
          const left = x > 0 ? (x < maxWidth ? x : maxWidth) : 0
          const top = y > 0 ? (y < maxHeight ? y : maxHeight) : 0
          if(this.props.setPanelPosition){
            this.props.setPanelPosition(left,top);
          }
        }
        this.activeAnimation = false;
      }
    }
  }
  onContentMouseMove(e){
    let obj = {};
    obj.target = this.titleDom;
    obj.pageX = e.pageX;
    obj.screenY = e.screenY;
    this.onMouseMove(obj);
  }
  onContentMouseUp(){
    this.onMouseUp();
  }
  onBackgroundMouseMove(e){
    let obj = {};
    obj.target = this.titleDom;
    obj.pageX = e.pageX;
    obj.screenY = e.screenY;
    this.onMouseMove(obj);
  }
  onBackgroundMouseUp(){
    this.onMouseUp();
  }
  //endregion

  //region request
  // 獲取滑鼠點擊title時的坐標、title的坐標以及兩者的位移
  getPosition (e) {
    // 標題DOM元素titleDom
    const titleDom = e.target
    // titleDom的坐標(視窗)
    const X = titleDom.getBoundingClientRect().left
    // 由於Y軸出現滾動條，需要與滑鼠保持一致，存儲頁面相對位置
    const Y = this.panelDom.offsetTop

    // 滑鼠點擊的坐標(頁面)
    let mouseX = e.pageX
    let mouseY = e.screenY
    // 滑鼠點擊位置與modal的位移
    const diffX = mouseX - X
    const diffY = mouseY - Y
    return {X, Y, mouseX, mouseY, diffX, diffY}
  }
  //endregion

  //region render
  //endregion

  //region clear
  //endregion

  render() {
    return (
      <>
      </>
    );
  }
}
export default Draggable;