第二种渲染方法没有被调用来显示Subview Backbone

Question

var $ = require('jquery'),
    Handlebars = require('handlebars'),
    Backbone = require('backbone'),
    mainchartTemplate = require('../../templates/dashboard/chartscontainer.html'),
    pieChartView = require('../../views/dashboard/PieChartView'),
    lineChartView = require('../../views/dashboard/LineChartView'),
    moment = require('moment');

var MainChartView = Backbone.View.extend({
    el: $('#id-charts-stats'),

    initialize: function() {

        this.pie = new pieChartView();
        this.line = new lineChartView();
    },
    events: {
        'click a.agraphType': "changeGraphData"
    },

    changeGraphData: function(ev) {
        ev.preventDefault();
        var type = $(ev.target).attr('type');
        sessionStorage.setItem("typeOfGraph", type);
        this.render();
    },

    render: function() {
        this.$el.html(mainchartTemplate);    
        this.line.setElement(this.$('#id-sales-line')).delegateEvents().render();
        this.pie.setElement(this.$('#id-sales-pie')).delegateEvents().render();
    }
});

module.exports = MainChartView;

我正在尝试渲染到SubViews但是我的代码没有运行第二个delegateEvents代码。