import React, { Component } from 'react';
import { SimpleStepper } from 'react-native-simple-stepper';

export default class App extends Component {
  constructor(props) {
    super(props);
    this.state = { value: 0 };
  }
  valueChanged(value) {
    // Truncate value to 2 decimal places and cast as Number.
    const nextValue = Number(value.toFixed(2));
    this.setState({ value: nextValue });
    // ...
  }
  render() {
    return <SimpleStepper valueChanged={value => this.valueChanged(value)} />;
  }
}