View 中 text 中使得text 垂直居中

        外层View
	positionHeader: {
		marginTop: h(4),
		marginBottom: h(8),
		borderWidth: StyleSheet.hairlineWidth,
		borderColor: '#2B98FE',
		borderRadius: wh(2),
		justifyContent: 'center',
		paddingLeft: w(3),
		paddingRight: w(3),
		paddingBottom: w(6),
		minHeight: h(17),
		alignSelf: 'flex-start',
	},
        
        text 不定义宽高
        
        注意点: 
        justifyContent: 'center', 必须写在paddingLeft: w(3),
		paddingRight: w(3),之前，否则无效