reactNative1 created by dantejauregui - https://repl.it/HxUR/4

rNativeSumButton1.js

import React from 'react';
import { StyleSheet, Text, View, Button, TextInput } from 'react-native';

export default class App extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      numero: 0,
      boxNumber: 0
    };
  }

  dante() {
    this.setState({
      numero: parseInt(this.state.numero) + parseInt(this.state.boxNumber),
    });

    this.setState({
      boxNumber: 0
    });
  }

  resetear() {
    this.setState({
      numero: 0
    });
  }

  render() {
    return (
      <View style={styles.container}>
        <Text style={{textAlign: 'center'}}>Selecciona varios números y adiciona asi más y más números:</Text>
        
        <TextInput
        style={{height: 40, width: 160, borderColor: 'gray', borderWidth: 1, textAlign: 'center', margin: 25}}
        onChangeText={(n) => this.setState({boxNumber: n})}
        value={this.state.boxNumber}
        keyboardType={'numeric'}
        />

        <View style={{alignItems: 'stretch', flexDirection: 'row', height: 40, marginBottom: 10, justifyContent: "space-between", width: 200}}>
          <Button
            onPress={this.dante.bind(this)}
            title="Adiciona N°"
            color="#841584"
            accessibilityLabel="Learn more about this purple button"
            style={{marginBottom: 10}}
          />
          <Button
            onPress={this.resetear.bind(this)}
            title="Resetea"
            color="#2f2f2f"
            accessibilityLabel="Learn more about this purple button"
          />
        </View>
        {/*<TouchableOpacity onPress={this.dante.bind(this)}>
          <Image
            style={styles.button}
            source={require('./myButton.png')}
          />
        </TouchableOpacity>*/}
        <Text style={{marginTop: 25, fontSize: 20}}>{this.state.numero}</Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
    marginTop: 0,
    marginBottom: 50
  },
});