Példák

Szerző: Sallai András
Copyright © Sallai András, 2021, 2023
Licenc: CC Attribution-Share Alike 4.0 International
Web: https://szit.hu

Számláló növelő

A példában osztályokat használunk:

import React, { Component} from 'react';
import { View, StyleSheet, Button, Text } from 'react-native';
 
export default class App extends Component {
  constructor() {
    super();
    this.state = {
      counter: 0
    }
  }
 
  increment = () => {    
    this.setState({ counter: this.state.counter + 1 });
  }
  render() {
    return (
      <View style={styles.container}>
        <Text>Számláló: {this.state.counter}</Text>
        <Button 
          title='Növel'
          onPress={this.increment} 
        />
      </View>
    );
  }
}
 
const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: 'skyblue',
    alignItems: 'center',
    justifyContent: 'center',
  },
});

Számláló kicsit másként

Teljes forráskód:

https://github.com/oktat/mobil_count.git

App.js

import { 
  StyleSheet, 
  Text, 
  View, 
  TextInput, 
  Button
} from 'react-native';
import {useState} from 'react';
 
export default function App() {
 
  const [counter, setCounter] = useState(0);
 
  function increment() {
    setCounter(counter + 1)
  }
  return (
    <View style={styles.container}>
      <Text style={styles.elso}>Számláló</Text>
 
      <TextInput 
      style={styles.input}      
      value={counter}
      />
 
      <Button title='Számol' 
      onPress={increment} 
      />
 
      <Text style={styles.elso}>
        {counter}
      </Text>
 
      <Button title="Nulla" onPress={ () => setCounter(0)} />
    </View>
 
  );
}
 
const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#008',
    alignItems: 'center',
    justifyContent: 'center',    
  },
  elso: {
    color: '#fff',
    fontSize: 30,
  },
  input: {
    backgroundColor: 'lightblue',
    width: '90%',
    fontSize: 30,
  },
});

Háromszög területe

App.js

import React from 'react';
import { Button, StyleSheet, Text, TextInput, View } from 'react-native';
 
export default function App() {
  const [base, setBase] = React.useState('');
  const [height, setHeight] = React.useState('');
  const [area, setArea] = React.useState('');
 
  const handleSubmit = () => {    
    let result = base*height/2;
    setArea(result);
  }
 
  return (
    <View style={styles.container}>      
 
      <Text style={styles.head}>Háromszög területe</Text>
      <Text>Alap:</Text>      
      <TextInput 
      style={styles.input}
      placeholder='Alap'
      onChangeText={(base) => setBase(base)}      
      />
 
      <Text>Magasság:</Text>      
      <TextInput 
      style={styles.input}
      placeholder='Magasság'
      onChangeText={(height) => setHeight(height)}      
      />
 
      <Text style={styles.area}>Terület: {area}</Text>
 
      <Button 
        title='Számít' 
        onPress={handleSubmit}
        />
 
    </View>
  );
}
 
 
 
const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
  input: {
    borderWidth: 1,
    borderColor: '#777',
    padding: 8,
    margin: 10, 
    width: 200,
  },
  area: {
    margin: 20,
  },
  head: {
    margin: 20,
    fontSize: 34,
  }
});