关于Highcharts的x轴密密麻麻的时间格式显示问题解决方法

把X轴改为这样
xAxis: {
categories:obj.tdate,   //x轴显示格式['0000-00-00','0000-00-00','0000-00-00','0000-00-00','4','5']
labels: {step:2,rotation: -25, align: 'right', style: { font: 'normal 13px Verdana, sans-serif'}}
},

function chart_line_basic(renderTo, categories, series, legendEnabled) {
this.renderTo = renderTo;
this.series = series;
this.categories = categories;
this.legendEnabled = legendEnabled;
this.step=0;
this.rotation=0;
if(categories.length>4)
{
this.step=2;
this.rotation=25;
}
}
chart_line_basic.prototype.formatterTooltip = function () { }
chart_line_basic.prototype.showChart = function () {
var chart;
chart = new Highcharts.Chart({
chart: {
renderTo: this.renderTo,
type: 'line',
//            marginRight: 130,
//            marginBottom: 25
},
title: {
text: '',
x: -20 //center
},
subtitle: {
text: '',
x: -20
},
xAxis: {
labels:{
step:this.step,
rotation: this.rotation
},
categories: this.categories
},
yAxis: {
title: {
text: ''
},
plotLines: [{
value: 0,
width: 1,
color: '#808080'
}]
},
tooltip: {
formatter: this.formatterTooltip
},
legend: {
floating: true,
layout: 'vertical',
align: 'right',
verticalAlign: 'top',
x: -10,
y: 20,
borderWidth: 0,
enabled: this.legendEnabled
},
series: this.series
});
};

<script type="text/javascript">
$(function () {
var renderTo = "container_1";
//如果没有可以用NULL表示：空 ，而0表示从0开始
var series = [{ name: 'Tokyo', data: [7.0, 6.9, null, 14.5, 18.2, 21.5, 25.2, 26.5]}];
var categories = ['一周', '二周', '三周', '四周', '五周', '六周', '七周', '八周'];
var legendEnabled = true;
var _line_basic = new chart_line_basic(renderTo, categories, series, legendEnabled);
_line_basic.formatterTooltip = function () { return this.x + ': ' + this.y + '%'; }
_line_basic.showChart();

});
</script>

<div id="container_1" style="min-width: 400px; height: 400px; margin: 0 auto"></div>