通过计算某个扇形区域的值占整个圆的百分比来得到这个扇形的角度，从而根据startAngle这个属性来设定图形的开始渲染的角度，使点击某个扇形时圆环旋转使之始终对准某个点。
期间考虑到某扇形区域太小点击不到，来设置最小扇形区域。
const myChartContainer = document.getElementById( 'chart' );
const myChart = echarts.init( myChartContainer );
let minAngle = 30;// 最小扇形区域为30
for ( let i = 0; i < obj.data.length; i++ ) { //某项数据为0时，最小扇形区域为0
if ( obj.data[ i ].value === 0 ) {
minAngle = 0;
break;
}
}
const pieValue = obj.data.map( v => {
return v.value;
} )
const sum = pieValue.reduce( ( prev, cur ) => {//数据值的总和
return prev + cur;
}, 0 );
const sum2 = pieValue.reduce( ( prev, cur ) => {
if ( cur < sum / 12 && cur > 0 ) {//某个值大于0小于总和的1/12即30时，按30计算和
return prev + sum / 12;
}
return prev + cur;
}, 0 );
let initPieValue = pieValue[ 0 ];// 初始值
if ( initPieValue < sum / 12 && initPieValue > 0 ) {
initPieValue = sum / 12;
}
const option = {
tooltip: {
show: false,
trigger: 'item',
formatter: '{a} <br/>{b}: {c} ({d}%)'
},
legend: {
show: false,
orient: 'vertical',
x: 'left'
},
color: [ '#44bbf8', '#93e588', '#ffd87b', '#f88071' ],
series: [
{
name: '',
type: 'pie',
radius: [ '45%', '79%' ],
clockWise: false,
startAngle: 167 - ( initPieValue / sum2 * 360 / 2 ),
minAngle: minAngle,
avoidLabelOverlap: false,
itemStyle: {
emphasis: {
radius: [ '46%', '100%' ]
}
},
label: {
normal: {
show: false,
position: 'center'
},
emphasis: {
show: false,
textStyle: {
fontSize: '30',
fontWeight: 'bold'
}
}
},
labelLine: {
normal: {
show: false
}
},
data: obj.data
}
]
};
myChart.setOption( option );
if ( minAngle === 30 ) { //最小扇形区域30时
myChart.dispatchAction( { type: 'highlight', seriesIndex: 0, dataIndex: 0 } );
}
let preDataIndex = 0;
myChart.on( 'click', ( v ) => {
if ( v.dataIndex === preDataIndex ) {
myChart.dispatchAction( {
type: 'highlight',
seriesIndex: 0,
dataIndex: v.dataIndex
} );
return;
}
const sum1 = pieValue.reduce( ( prev, cur, index ) => {
if ( index < v.dataIndex ) {
if ( cur < sum / 12 && cur > 0 ) {
return prev + sum / 12; // 饼图的扇形最小角度设置为30，占圆的1/12
}
return prev + cur;
}
return prev;
}, 0 );
let curPieValue = pieValue[ v.dataIndex ];
if ( curPieValue < sum / 12 && curPieValue > 0 ) {
curPieValue = sum / 12;
}
option.series[ 0 ].startAngle = 167 - ( sum1 / sum2 * 360 + curPieValue / sum2 * 360 / 2 );// 开始渲染图形的角度
myChart.setOption( option );
preDataIndex = v.dataIndex;
window.setTimeout( () => {
myChart.dispatchAction( {
type: 'highlight',
seriesIndex: 0,
dataIndex: v.dataIndex
} );
}, 400 );
this.mrkName = v.data.name;
this.mrkValue = v.data.value;
} );