JSX 部分如下所示：

<span className="header_srh_i_c" onMouseDown={this.toggleSearchbar}>
    <i className="fa fa-search"
        id="searchButton"
        name="searchButton"
     />
 </span>

同一组件中的函数如下所示：

toggleSearchbar(event){
    const eventType = event.type;
    if(this.state.showSearch && this.props.q && length(this.props.q) > 0){
      this.toggleSearching();
    }else{
      console.log("state after", this.state.showSearch)  //false

      this.setState({showSearch:!this.state.showSearch},function (event) {
      console.log("state after", this.state.showSearch) //false
      })
    }
  }

false执行后状态保持事件

this.setState({showSearch:!this.state.showSearch},function (event) {
          console.log("state after", this.state.showSearch) //false
          })

但是，如果我使用onClick而不是onMouseDown