How do Textinput print number 1 every time you press Buttom?

Question

How to do the TextInput print out the number 1 every time we press the button?

Example: if I press 5 times the button, I want "11111" to appear on TextInput.

const App = () => {

  const state={
    newNumber: 1,
    number: ''
  };

  const printNumber = () => {
     const resultado = this.state.newNumber;

     this.setState({
       number: resultado
     });
  }

  return (
    <View style={styles.container}>
      
      <TextInput
        style={styles.input}
         value={this.number}
        onChangeText={(text) =>this.setState({number})}
      />
      
      <Button title="1" onPress={printNumber} />
    </View>
  );
}

Answer 1

You have a problem with your code React-Hooks in your code, you cannot start the same state was with component (see my example).

Basically, the code is to concatenate the existing values with a text that represents the number "1", that in the language needs the value to be concatenated to be a text, minimum example:

const App = () => {
  const [n, setN] = React.useState(''); 
  const handleChange = (e) => setN(state => state + "1");
  return (
    <div>
      <input type="text" value={n} onChange={e => setN(e.target.value)} />
      <button onClick={handleChange}>adicionar</button>
    </div>
  )
}

ReactDOM.render( <App/> , document.getElementById('root'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.9.0/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.9.0/umd/react-dom.production.min.js"></script>
<div id="root">Carregando ...</div>

^{Observing: the snippet here is reactjs, but the concept is the same for React-Native}

---

In your code it’s basically:

const App = () => {
    const [number, setNumber] = React.useState(''); 
    
    const printNumber = () => {
        setNumber(state => state + "1");
    }
    
    return (
        <View style={styles.container}>   
            <TextInput
                style={styles.input}
                value={this.number}
                onChangeText={(text) => setNumber(state => state + text)}
            />    
            <Button title="1" onPress={printNumber} />
        </View>
    );
}

this way will work typing and also when press the button.