在悬停

Question

我想实现一个drop系统，如果drop目标是嵌套的，你可以使用鼠标滚轮在它们之间循环（或者在一定时间后发生自动循环）这将特别有用，因为许多嵌套目标在屏幕上占据完全相同的区域。

我目前正在考虑我可以使用从容器传下来的回调，当调用悬停函数/当isOver prop更改时它可以被drop目标用来注册/取消注册，但它＆＃39 ; s非常耦合，我必须从容器传递道具到DropTargets，在现实世界的应用程序中，容器和放置目标之间将有未知数量的级别，所以我可能不得不设置某种回调系统，整体而言不是理想的解决方案。此外，我不确定如何在骑行时确保正确的顺序，因为放置目标不知道它们的嵌套程度如何（请参阅下面的代码，了解我是如何实现这一点的）。有没有更简洁的方法来实现这样的系统？

@DragDropContext(HTML5Backend)
export default class Container extends Component {
  constructor (props) {
    super(props);
    this.state = {
      bins: []
    };
    this.status = {};
    this._cycle = this.cycle.bind(this);
    this._register = this.register.bind(this);
    this._deregister = this.deregister.bind(this);
  }

  componentWillUnmount () {
    if (this.timer) {
      window.clearInterval(this.timer);
    }
  }

  register (name) {
    if (this.state.bins.findIndex(e => e === name) === -1) {
      this.setState({
        bins: this.state.bins.concat(name)
      });
      if (!this.timer) {
        this.cycledBins = [];
        this.timer = window.setInterval(this._cycle, 3000);
        this._cycle();
      }
    }
  }

  deregister (name) {
    if (this.state.bins.findIndex(e => e === name) !== -1) {
      const bins = this.state.bins.filter((e) => e === name);
      this.setState({
        bins
      });
      if (!bins.length) {
        window.clearInterval(this.timer);
        this.timer = undefined;
      }
    }
  }

  cycle () {
    this.status = {};
    const bins = this.state.bins;
    let activeBin = -1;
    for (let i = 0; i < bins.length; i += 1) {
      if (this.cycledBins.findIndex(bin => bin === bins[i]) === -1) {
        activeBin = bins[i];
        break;
      }
    }
    if (activeBin === -1) {
      activeBin = bins[0];
      this.cycledBins = [];
    }
    this.cycledBins.push(activeBin);
    this.activeBin = activeBin;
    this.status[activeBin] = {
      isActive: true,
      isOnlyActive: bins.length === 1
    }
    this.forceUpdate();
  }

  render () {
    return (
      <div>
        bins = {JSON.stringify(this.state.bins)}<br />
        cycledBins = {JSON.stringify(this.cycledBins)}
        <div style={{ overflow: 'hidden', clear: 'both' }}>
          <Dustbin name="Outer" register={this._register} deregister={this._deregister} status={this.status["Outer"]} >
            <Dustbin name="Middle" register={this._register} deregister={this._deregister} status={this.status["Middle"]} >
              <Dustbin name="Inner" register={this._register} deregister={this._deregister} status={this.status["Inner"]} />
            </Dustbin>
          </Dustbin>
        </div>
        <div style={{ overflow: 'hidden', clear: 'both' }}>
          <Box name='Glass' />
          <Box name='Banana' />
          <Box name='Paper' />
        </div>
      </div>
    );
  }
}


const boxTarget = {
  hover(props) {
    props.register(props.name);
  }
};

@DNDDropTarget('Box', boxTarget, (connect, monitor) => ({
  connectDropTarget: connect.dropTarget(),
  isOver: monitor.isOver()//,
  //canDrop: monitor.canDrop()
}))
export default class Dustbin extends Component {
  static propTypes = {
    connectDropTarget: PropTypes.func.isRequired,
    isOver: PropTypes.bool.isRequired//,
    //canDrop: PropTypes.bool.isRequired
  };

  componentWIllMount () {
    if (!this.props.isOver) {
      this.props.deregister(this.props.name);
    }
  }

  componentWillReceiveProps (nextProps) {
    if (nextProps.isOver !== this.props.isOver && !nextProps.isOver) {
      this.props.deregister(this.props.name);
    }
  }

  render() {
    const { canDrop, isOver, connectDropTarget, status } = this.props;

    const isOnlyActive = status && status.isOnlyActive;
    let isActive = status && status.isActive;

    if (!isOver && isActive) {
      isActive = false;
    }

    return connectDropTarget(
      <div>
        <DropTarget position={BEFORE} shown={isActive} />
        { isActive && !isOnlyActive ? '(' + this.props.name + ')' : undefined }
        { this.props.children ? this.props.children : (
          <div style={style}>
            { isActive ?
              'Release to drop' :
              'Drag a box here'
            }
          </div>
        ) }
        <DropTarget position={AFTER} shown={isActive} />
      </div>
    );
  }
}