环形图百分比不显示

canvaRing = new uCharts({
$this: this,
canvasId: canvasId,
type: 'ring',
fontSize: 11,

            legend: true,  
            // title: {  
            //  name: '70%',  
            //  color: '#7cb5ec',  
            //  fontSize: 25 * this.pixelRatio,  
            //  offsetY: 3 * this.pixelRatio  
            // },  
            // subtitle: {  
            //  name: '12312',  
            //  color: '#666666',  
            //  fontSize: 15 * this.pixelRatio,  
            //  offsetY: 30 * this.pixelRatio  
            // },  

            extra: {  
                pie: {  
                    offsetAngle: -45,  
                    ringWidth: 25 * this.pixelRatio,  
                    labelWidth: 15  
                }  
            },  
            background:'#FFFFFF',  
            pixelRatio: this.pixelRatio,  
            series: chartData,  
            animation: true,  
            width: this.cWidth * this.pixelRatio,  
            height: this.cHeight * this.pixelRatio,  
            disablePieStroke: true,  
            dataLabel: true  
        });