picker-example.js

import React from 'react';
import { View, Picker, StyleSheet } from 'react-native';
import PropTypes from 'prop-types';
const PickerExample = ({elements}) => (
  <View>
    <Picker
      mode={Platform.OS === 'ios' ? 'dialog' : 'dropdown'}
      style={styles.picker}
      selectedValue={this.state.quantityType}
      onValueChange={this.changeType}
      itemStyle={styles.pickerItems}
    >
      {elements.map(element => <Picker.Item label={element.label} value={element.value}/>)}
    </Picker>
  </View>
)

PickerExample.propTypes = {
  elements: PropTypes.arrayOf(
    PropTypes.shape({
      label: PropTypes.string,
      value: PropTypes.string,
    })
  )
}

const styles = StyleSheet.create({
  picker: {
    flex: 2,
    backgroundColor: '#E0E0E0',
    height: 40,
  },
  pickerItems: {
    height: 40,
  },
});