React Native中底部导航器中的阴影

Question

如何在React Native的downtabnavigator中设置阴影？

我尝试了这段代码

shadow: {
    shadowOpacity: 0.7,
    shadowRadius: 2,
    elevation: 2,
    borderWidth:1,
    borderColor:'#ddd',
    shadowColor:'#000',
    shadowOffset:{width: 0, height: 2},
    shadowOpacity:0.8,
    elevation:1,
}