echarts环形图，自定义说明文字

一、代码

 app.title = '已安装通讯盒电站统计';

 option = {
      backgroundColor: '#0f0f31',//#0f0f31
     title: {
         show:true,
         x:"left",
         text: '已安装通讯盒电站统计',
         textStyle:{
             fontSize:16
             ,fontWeight:'normal'
             ,color:'#72a1d2'
         },
         left:20,
         top:10,
         borderColor :'#10395c',
         borderWidth :2,
     },
     tooltip: {
         trigger: 'item',
         formatter: "{a} <br/>{b}: {c} ({d}%)"
     },

     graphic: [ {
         type: 'group',
         id: 'textGroup2',
         left: 370,
         top: 400,
         position :[10, 0],
         children: [

             {
                 type: 'text',
                 z: 100,
                 top: 'middle',
                 left: 100,
                 style: {
                     formatter: "{a} <br/>{b}: {c} ({d}%)",
                     text: [
                         '已安装1280个',
                         '未安装320个',
                     ].join('\n'),
                     font: '16px cursive',
                     textVerticalAlign :'middle',
                     fill:'#13a7d1',

                 }
             }
         ]
     }],
     series: [
         {
             name:'已安装通讯盒电站统计',
             type:'pie',
             radius:['10%','18%'],
             avoidLabelOverlap:false,
             color:['#32A8FF',' #02C800','#9f47fd'],
             formatter: '{b}: {d}',
             slient:true,
             markLine :{
                 label  :{
                     show:true,
                     position :'outside'
                 },
             },
             labelLine:{
                 normal:{
                     show:true,
                     length:14  ,
                     length2 :56,
                 }
             },
             label:{
               normal:{
                   show:true,
                   position:'center',
                   formatter:function(){
                       return '80%'
                   },
                   textStyle:{
                       fontSize:20,
                       color:'rgba(20, 180, 213, 0.9)',
                   }
               }
             },
             emphasis:{
               show:true,
               textStyle:{
                   fontSize:30,
                   //fontWeight:'bold'
               }
             },

             data:[{value:1280,name:'已安装',itemStyle:{
                 normal:{
                     color: new echarts.graphic.LinearGradient(0, 1, 1, 0, [{
                         //颜色渐变函数 前四个参数分别表示四个位置依次为左、下、右、上

                         offset: 0,
                         color: '#2a8af6'
                     }, {
                         offset: 1,
                         color: '#393eda'
                     }])
                 },emphasis : {
                     label : {
                         show : true,
                         formatter : "{b}\n{d}%",
                         color:'white',
                     }
                 }
             }},{value:320,name:'未安装',itemStyle:{
                 normal:{
                     color:'transparent',
                 }
             }}]
         },{
             name:'',
             type:'pie',
             radius:['8%','10%'],
             avoidLabelOverlap:false,
             legendHoverLink :false,
             label:{
               show:false,
             },
             tooltip:{//禁止鼠标悬停显示提示框
                 show:false,
             },
             hoverAnimation:false ,//禁止鼠标悬停放大区域
             color:['#bcdbfa'],

             data:[{value:100}]
         }
     ]
 };

二、效果图