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('
'),
                    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}
{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