多个X轴的时候，echarts需要设定x轴的gridIndex，以及Y轴对应的xAxisIndex

function LineChart2(name,subtitle,placeholder, xaxis,xaxis2, ylines, unit, high, low) {

this.placeholder=placeholder;

this.option=this.getDefaultOption();

this.option.title.text=name;

this.option.title.subtext=subtitle;

this.option.xAxis[0].data=xaxis.data;

this.option.xAxis[0].name=xaxis.name;

this.option.xAxis[0].type=xaxis.type||"category";

this.option.xAxis[0].gridIndex=0;

this.option.xAxis[1].data=xaxis2.data;

this.option.xAxis[1].name=xaxis2.name;

this.option.xAxis[1].type=xaxis2.type||"category";

this.option.xAxis[1].gridIndex=1;

this.setLegend(ylines);

this.setSeries(ylines);

this.option.yAxis[0].axisLabel.formatter="{value}"+unit;

this.draw();

}

LineChart2.prototype.setSeries=function(ylines) {

for(var i=0;i<ylines.length;i++){

this.option.series.push({

name: ylines[i].name,

type: "line",

data: ylines[i].points,

symbol:"none",

color:ylines[i].color,

xAxisIndex:i

});

}

}