您可以调用onLayout事件来测量元素：

measureView(event) {
  console.log('event properties: ', event);
  console.log('width: ', event.nativeEvent.layout.width)
}

<View onLayout={(event) => this.measureView(event)}>

至于宽度和高度的百分比，你可以得到窗口的宽度和高度，并像这样使用它们：

const {
    ...
    Dimensions
} = React

const width = Dimensions.get('window').width
const height = Dimensions.get('window').height

// 80% width
width: width * .8,

// 25% height
height: height / 4,