1.modal点击其他区域消失

<TouchableWithoutFeedback
    onPress={()=>this.setState({showTopMenu:false})}>
    <View style={{position: 'absolute',left: 0,right: 0,top: 0,bottom: 0,width: null,}}/>
</TouchableWithoutFeedback>

2.图片做背景

<Image  style={styles.img}
    source={require('../image/IMG_0026.jpg')}
    resizeMode='cover' />

img: {
    position: 'absolute', left: 0, right: 0, top: 0, bottom: 0, height: null, width: null,},