勢在必行的傾聽者

你還可以使用 Polymer 的 listen 和 unlisten 方法強制新增/刪除偵聽器

    <dom-module id="imparative-listener">
      <template>
        <style>
          #inner{
            width: 200px;
            height: 50px;
            border: 1px solid blue;
            margin-top: 15px;
          }
        </style>
        <div id="inner">I've imparative listener attached</div>
      </template>
    </dom-module>
    <script>
      Polymer({
        is:'imparative-listener',
        
        //keeping it in attached to make sure elements with their own shadow root are attached
        attached:function(){
          this.listen(this.$.inner,'track','trackDetails'); // For more details on method check https://www.polymer-project.org/1.0/docs/api/Polymer.Base#method-listen
        },
        
        //all the listener functions have event as first parameter and detail (event.detail) as second parameter to the function
        trackDetails:function(e,detail){
          if(detail.state=='end'){
            alert('Track distance x:'+detail.dx+' y:'+detail.dy);// For more details on track event check https://www.polymer-project.org/1.0/docs/devguide/gesture-events
      }
    }
  })
</script>