text: import React from 'react';
  import { StyleSheet, TextInput, Text, View } from 'react-native';
  
  
  export default class App extends React.Component {
    constructor(props){
      super(props);
      this.state = {
        cuadro1: 7, 
        cuadro2: 0,    
      };
    };
  
    suma = (a, b) =>{
      let res = a + b;
      console.warn(res);
      return res;
    } ;
  
    cuadro1_cambia = (loqueescriben)=>{
      let num = parseInt(loqueescriben);
  
      if(isNaN(num))
      {
        num = 0;
      }
  
      this.setState(
        {
          cuadro1: num
        }
      );
    }; 
  
    cuadro2_cambia = (loqueescriben)=>{
        {
          this.setState({cuadro2: parseInt(loqueescriben)});
        }     
      };
  
    render() {
      return (
        <View style={{margin:50}}> 
  
          <TextInput 
            value={this.state.cuadro1.toString()}
            onChangeText={this.cuadro1_cambia}
         />      
  
          <TextInput 
            value={this.state.cuadro2.toString()}
            onChangeText={this.cuadro2_cambia}
          />
          
          <TextInput 
            value={this.suma(this.state.cuadro1,this.state.cuadro2).toString()}
            />
        </View>
      );
    }
  } 
  
  