父组件中
 <div class="chart" shadow="always">
  <objEcharts :devicePressure="pressure"></objEcharts>
 </div>

子组件中
export default {
 props: {
  devicePressure: { type: String, require: true },
 },
 data() {
  return {
   upPressure: this.devicePressure,
  };
 },

watch: {
 	//监听devicePressure的数据变化。
  devicePressure(newData, oldData) {
  //把更新后的数据newData，赋值给需要传入echarts中的参数。
   this.upPressure = newData;
  //一定要调用echarts实例，要不然echarts不实时展示。
   this.drawLine();
  },
 },

export default {
 props: {
  devicePressure: { type: String, require: true },
 },
 data() {
  return {
   upPressure: this.devicePressure,
  };
 },
 mounted() {
  this.drawLine();
 },
 watch: {
  	devicePressure(newData, oldData) {
   this.upPressure = newData;
   this.drawLine();
  },
 },
methods: {
  drawLine() {
   // 基于准备好的dom，初始化echarts实例
   let visualOneChart = this.$echarts.init(document.getElementById("visualOneChart"));
   // 绘制图表
   visualOneChart.setOption({
    tooltip: {
     formatter: "{a} <br/>{b} : {c}Pa",
    },
    series: [
     {
      name: "压力值",
      type: "gauge",
      clockwise: true,
      detail: {
       formatter: this.upPressure,
       textStyle: {
        fontSize: 14,
       },
      },
      data: [{ value: this.upPressure, name: "压力值" }],
      radius: "90%",
      axisLabel: {// 刻度标签。
       show: true,
       distance: -5,
       color: "black", 
       fontSize: 10, 
       formatter: "{value}", 
      },
      axisLine: {// 仪表盘轴线(轮廓线)相关配置。
       show: true, 
       lineStyle: {// 仪表盘轴线样式。
        opacity: 1, 
        width: 15, 
        shadowBlur: 10, 
       },
      },
      pointer: { // 仪表盘指针。
       show: true,
       length: "70%", 
       width: 4, 
      },
     },
    ],
   });
  },
 },
}