echarts柱形图如何设置单击选中效果echarts 柱状配置项内容和展示

点击某一个柱子，鼠标移开后，想要该柱子保持一个选中的状态，比如高亮。试过dispactAction方法，行不通，求大佬们分享解决方案。。

      var option = {
    color: [{
                type: 'linear',
                x: 0,
                y: 0,
                x2: 0,
                y2: 1,
                colorStops: [{
                    offset: 0,
                    color: '#00a1e9' // 0% 处的颜色
                                }, {
                    offset: 1,
                    color: '#01e3ae' // 100% 处的颜色
                                }],
                globalCoord: false // 缺省为 false
            }],
            backgroundColor: '#04225e',
            legend: {
                top: 8,
                right: 28,
                itemWidth: 17,
                itemHeight: 12,
                data: ['次数'],
                textStyle: {
                    color: '#00c0ff',
                    fontSize: 14,
                },
                borderRadius: 0
            },
            tooltip: {
                trigger: 'axis',
                axisPointer: { // 坐标轴指示器，坐标轴触发有效
                    type: 'shadow' // 默认为直线，可选为：'line' | 'shadow'
                },
                formatter: '{b}：{c}',
                backgroundColor: '#009ffc'
            },
            grid: {
                left: 30,
                right: 30,
                top: 40,
                bottom: 40,
                containLabel: true
            },
            xAxis: [
                {
                    type: 'category',
                    data: ['2017/01', '2017/02', '2017/03', '2017/04', '2017/05', '2017/06', '2017/07', '2017/08', '2017/09', '2017/10', '2017/11', '2017/12'],
                    axisLine: {
                        lineStyle: {
                            color: '#06358f',
                        }
                    },
                    axisTick: {
                        show: false
                    },
                    axisLabel: {
                        color: '#00c0ff'
                    }
                }
            ],
            yAxis: [
                {
                    type: 'value',
                    name: '（单位：次）',
                    nameTextStyle: {
                        color: '#00c0ff'
                    },
                    splitNumber: 5,
                    splitLine: {
                        show: true,
                        lineStyle: {
                            color: '#025ea8'
                        }
                    },
                    axisLine: {
                        show: false
                    },
                    axisTick: {
                        show: false
                    },
                    axisLabel: {
                        color: '#00c0ff'
                    }
                }
            ],
            series: [
                {
                    name: '次数',
                    type: 'bar',
                    barWidth: 25,
                    data: [40, 78, 25, 42, 68, 25, 54, 43, 48, 56, 42, 50],
                    itemStyle: {
                        normal: {
                            opacity: 0.5
                        },
                        emphasis: {
                            opacity: 1
                        }
                    }
                }
            ]
};
myChart.setOption(option);
myChart.on('click', function (params) {
    console.log(params.name);
    applyChart.dispatchAction({
        type: 'highlight',
        seriesIndex: 0,
        name: params.name
    });
});
myChart.dispatchAction({
    type: 'highlight',
    seriesIndex: 0,
    name: '2017/12'
});