Using querySelector to find nested elements inside a Polymer template returns null
document.querySelector('paper-tabs');doesn't find the paper-tabs element, because it is hidden inside the shadow DOM of the tab-list element.
You can simply give paper-tabs an id, say tabs, and access it like so
this.$.tabs(See http://www.polymer-project.org/docs/polymer/polymer.html#automatic-node-finding.)
There is also the option to access the shadow DOM directly
this.shadowRoot.querySelector('paper-tabs');If you only want to listen for changes on the paper-tabs selection, you can use a change watcher:
<paper-tabs selected="{{currentTab}}">Polymer('tab-list', { currentTab: 'all', currentTabChanged: function() { console.log(this.currentTab); }});(See http://www.polymer-project.org/docs/polymer/polymer.html#change-watchers)
<template is="dom-repeat" items="{{dataobject}}"> <div on-tap="_showdetail"> <iron-collapse id="collapse">??</iron-collapse> </div> </template>And to toggle the iron-collapse elements inside the dom-repeat I use
_showdetail: function(e){ Polymer.dom(e.currentTarget).querySelector('#collapse').toggle();},