React Nativeの基本コンポーネント(View, Text, Image)を徹底解説

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

const App = () => {
  return (
    <View style={styles.container}>
      <View style={styles.box1} />
      <View style={styles.box2} />
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#f0f0f0',
  },
  box1: {
    width: 100,
    height: 100,
    backgroundColor: 'blue',
  },
  box2: {
    width: 100,
    height: 100,
    backgroundColor: 'red',
    marginTop: 20,
  },
});

export default App;

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

const App = () => {
  return (
    <View style={styles.container}>
      <Text style={styles.title}>React Nativeの世界へようこそ！</Text>
      <Text style={styles.subtitle}>
        Textコンポーネントを使って、テキストを表示してみましょう。
      </Text>
      <Text style={styles.clickable} onPress={() => alert('テキストがクリックされました！')}>
        ここをタップしてください。
      </Text>
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#fff',
  },
  title: {
    fontSize: 24,
    fontWeight: 'bold',
    marginBottom: 10,
  },
  subtitle: {
    fontSize: 16,
    color: '#666',
    marginBottom: 20,
  },
  clickable: {
    fontSize: 18,
    color: 'blue',
    textDecorationLine: 'underline',
  },
});

export default App;

import React from 'react';
import { Image, View, StyleSheet } from 'react-native';

const App = () => {
  return (
    <View style={styles.container}>
      <Image
        source={require('./assets/local-image.png')} // ローカル画像
        style={styles.localImage}
      />
      <Image
        source={{ uri: 'https://example.com/remote-image.jpg' }} // リモート画像
        style={styles.remoteImage}
        resizeMode="contain"
      />
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#fff',
  },
  localImage: {
    width: 100,
    height: 100,
    marginBottom: 20,
  },
  remoteImage: {
    width: 200,
    height: 200,
  },
});

export default App;

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

const ProfileCard = () => {
  return (
    <View style={styles.card}>
      <Image
        source={{ uri: 'https://example.com/profile-pic.jpg' }}
        style={styles.profileImage}
      />
      <View style={styles.infoContainer}>
        <Text style={styles.name}>山田 太郎</Text>
        <Text style={styles.description}>React Nativeエンジニア</Text>
      </View>
    </View>
  );
};

const styles = StyleSheet.create({
  card: {
    flexDirection: 'row',
    padding: 10,
    borderWidth: 1,
    borderColor: '#ddd',
    borderRadius: 8,
    backgroundColor: '#fff',
    shadowColor: '#000',
    shadowOpacity: 0.1,
    shadowRadius: 4,
    shadowOffset: { width: 0, height: 2 },
    alignItems: 'center',
    margin: 10,
  },
  profileImage: {
    width: 60,
    height: 60,
    borderRadius: 30,
  },
  infoContainer: {
    marginLeft: 10,
    flex: 1,
  },
  name: {
    fontSize: 18,
    fontWeight: 'bold',
  },
  description: {
    fontSize: 14,
    color: '#666',
    marginTop: 5,
  },
});

export default ProfileCard;

<View style={{ flex: 1, backgroundColor: 'blue' }} />

<Image source={require('./assets/image.png')} style={{ width: 100, height: 100 }} />
<Image source={{ uri: 'https://example.com/image.jpg' }} style={{ width: 100, height: 100 }} />

<Text style={{ fontSize: 16, color: 'black' }}>テキスト例</Text>

// 正しい例
<View>
  <Text>正しい構造</Text>
</View>

<View style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}>
  <Text>中央に配置</Text>
</View>

import React from 'react';
import { View, Text, Image, FlatList, StyleSheet } from 'react-native';

const profiles = [
  { id: '1', name: '山田 太郎', description: 'React Nativeエンジニア', image: 'https://example.com/profile1.jpg' },
  { id: '2', name: '佐藤 花子', description: 'デザイナー', image: 'https://example.com/profile2.jpg' },
  { id: '3', name: '鈴木 次郎', description: 'バックエンド開発者', image: 'https://example.com/profile3.jpg' },
];

const ProfileCard = ({ name, description, image }) => (
  <View style={styles.card}>
    <Image source={{ uri: image }} style={styles.profileImage} />
    <View style={styles.infoContainer}>
      <Text style={styles.name}>{name}</Text>
      <Text style={styles.description}>{description}</Text>
    </View>
  </View>
);

const App = () => {
  return (
    <FlatList
      data={profiles}
      renderItem={({ item }) => (
        <ProfileCard
          name={item.name}
          description={item.description}
          image={item.image}
        />
      )}
      keyExtractor={(item) => item.id}
      contentContainerStyle={styles.list}
    />
  );
};

const styles = StyleSheet.create({
  list: {
    padding: 10,
  },
  card: {
    flexDirection: 'row',
    padding: 10,
    borderWidth: 1,
    borderColor: '#ddd',
    borderRadius: 8,
    backgroundColor: '#fff',
    shadowColor: '#000',
    shadowOpacity: 0.1,
    shadowRadius: 4,
    shadowOffset: { width: 0, height: 2 },
    alignItems: 'center',
    marginBottom: 10,
  },
  profileImage: {
    width: 60,
    height: 60,
    borderRadius: 30,
  },
  infoContainer: {
    marginLeft: 10,
    flex: 1,
  },
  name: {
    fontSize: 18,
    fontWeight: 'bold',
  },
  description: {
    fontSize: 14,
    color: '#666',
    marginTop: 5,
  },
});

export default App;

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

const LoginForm = () => {
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');

  const handleLogin = () => {
    Alert.alert('ログイン情報', `Email: ${email}, Password: ${password}`);
  };

  return (
    <View style={styles.container}>
      <Text style={styles.label}>メールアドレス</Text>
      <TextInput
        style={styles.input}
        placeholder="Email"
        keyboardType="email-address"
        value={email}
        onChangeText={setEmail}
      />
      <Text style={styles.label}>パスワード</Text>
      <TextInput
        style={styles.input}
        placeholder="Password"
        secureTextEntry
        value={password}
        onChangeText={setPassword}
      />
      <Button title="ログイン" onPress={handleLogin} />
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    padding: 20,
  },
  label: {
    fontSize: 16,
    marginBottom: 5,
  },
  input: {
    borderWidth: 1,
    borderColor: '#ddd',
    borderRadius: 5,
    padding: 10,
    marginBottom: 15,
    fontSize: 16,
  },
});

export default LoginForm;