xAxis : [
    {
        type : 'value',
        axisLabel:{
            formatter: function (data) {
                return (Math.abs(data));
            }
        }
    }
],

series : [ { name:'iOS',  type:'bar',  stack: '总量',  label: { normal: { show: true  } },  data:null,    },  { name:'Android',  type:'bar',  stack: '总量',  label: { normal: { show: true,  position: 'left',  formatter: function (value) { return (Math.abs(value.data));  } } },  data:null,   } ]