| Engineering | Development | Mobile | React Native Crash Course 2020
React Native Crash Course 2020
Page Outline

https://www.youtube.com/watch?v=Hf4MJH0jDb4

What is React Native

Single Codebase

Requirements

iOS: Latest Xcode & iOS Simulator
Android: Android Studio / SDK / Emulator (AVD)

Components

Getting Started

Install ReactNative, Xcode, Andoird Studio
- https://reactnative.dev/docs/environment-setup
- https://developer.apple.com/xcode/. Open XCode simulator using open -a Simulator from terminal
- https://developer.android.com/studio

Create a new project using npx react-native init ShoppingList

Note if you encounter an error

Try `/Users/username/Library/Caches/CocoaPods/Pods/Release/Flipper-Glog/0.3.6-1dfd6/missing --help' for more information
configure: WARNING: 'missing' script is too old or missing

Go to XCode => Preferences => Location and Select the XCode Location. https://github.com/facebook/react-native/issues/29203

Start the applications
- For iOS: npx react-native run-ios
- For Android: npx react-native run-android

Installing Libraries

Vector icons
npm i react-native-vector-icons or using yarn yarn add react-native-vector-icons
npx react-native link react-native-vector-icons

UUID
npm i uuidv4 or using yarn yarn add uuidv4

Functional or Class Components

Two ways to write components using class or functions. https://djoech.medium.com/functional-vs-class-components-in-react-231e3fbd7108

For this tutorial we will be using Functional Components

Using Inline Styling

App.js

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

const App = () => {
  return (
    <View style={{flex: 1, justifyContent: 'center', alignItems: 'center'}}>
      <Text style={{color: 'darkslateblue', fontSize: 30}}>Hello World</Text>
    </View>
  )
}

export default App;

https://reactnative.dev/docs/view

Using StyleSheet

App.js

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

const App = () => {
  return (
    <View style={styles.container}>
      <Text style={styles.text}>Hello World</Text>
      <Image source={{uri: 'https://randomuser.me/api/portraits/men/1.jpg'}} style={styles.img} />
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
  text: {
    color: 'darkslateblue',
    fontSize: 30,
  },
  img: {
    width: 100,
    height: 100,
    borderRadius: 100 / 2
  },
});

export default App;

Creating a Header

App.js

import React from 'react';
import { View, Text, StyleSheet } from 'react-native';
import Header from './components/Header';

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

const styles = StyleSheet.create({
  container: {
    flex: 1,
    paddingTop: 60,
  },
});

export default App;

components/Header.js

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

const Header = () => {
  return (
    <View style={styles.header}>
      <Text style={styles.text}>Shopping List</Text>
    </View>
  )
}

const styles = StyleSheet.create({
  header: {
    height: 60,
    padding: 15,
    backgroundColor: 'darkslateblue',
  },
  text: {
    color: 'white',
    fontSize: 23,
    textAlign: 'center',
  },
});

export default Header;

Using Props

App.js

import React from 'react';
import { View, Text, StyleSheet } from 'react-native';
import Header from './components/Header';

const App = () => {
  return (
    <View style={styles.container}>
      <Header title="Shopping List" />
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    paddingTop: 60,
  },
});

export default App;

components/Header.js

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

const Header = (props) => {
  return (
    <View style={styles.header}>
      <Text style={styles.text}>{props.title}</Text>
    </View>
  )
}

const styles = StyleSheet.create({
  header: {
    height: 60,
    padding: 15,
    backgroundColor: 'darkslateblue',
  },
  text: {
    color: 'white',
    fontSize: 23,
    textAlign: 'center',
  },
});


Header.defaultProps = {
    title: 'Default Title'
}

export default Header;

Using State and Deleting an Item

App.js

import React, {useState} from 'react';
import { View, Text, StyleSheet, FlatList } from 'react-native';
import Header from './components/Header';
import ListItem from './components/ListItem';

const App = () => {
  const [items, setItems] = useState([
    {id: '1', text: 'Milk'},
    {id: '2', text: 'Eggs'},
    {id: '3', text: 'Bread'},
    {id: '4', text: 'Bagel'},
  ]);
  const deleteItem = (id) => {
    setItems(prevItems => {
      return prevItems.filter(item => item.id != id);
    });
  };
  return (
    <View style={styles.container}>
      <Header title="Shopping List" />
      <FlatList 
        data = {items}
        renderItem={({item}) => (
        <ListItem item={item} deleteItem={deleteItem} />
        )}
      />
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    paddingTop: 60,
  },
});

export default App;

components/ListItem.js

import React from 'react';
import { View, Text, StyleSheet, TouchableOpacity } from 'react-native';
import Icon from 'react-native-vector-icons/dist/FontAwesome'

const ListItem = ({item, deleteItem}) => {
  return (
    <TouchableOpacity style={styles.listItem}>
      <View style={styles.listItemView}>
          <Text style={styles.listItemText}>{item.text}</Text>
          <Icon name="remove" size={20} color="firebrick" 
          onPress={() => deleteItem(item.id)} />
      </View>
    </TouchableOpacity>
  );
};

const styles = StyleSheet.create({
    listItem: {
        padding: 15,
        backgroundColor: '#f8f8f8',
        borderBottomWidth: 1,
        borderColor: '#eee',
    },
    listItemView: {
        flexDirection: 'row',
        justifyContent: 'space-between',
        alignItems: 'center',
    },
    listItemText: {
        fontSize: 18,
    }
});

export default ListItem;

Deleting an Item

App.js

import React, {useState} from 'react';
import { View, Text, StyleSheet, FlatList } from 'react-native';
import Header from './components/Header';
import ListItem from './components/ListItem';
import AddItem from './components/AddItem';

const App = () => {
  const [items, setItems] = useState([
    {id: '1', text: 'Milk'},
    {id: '2', text: 'Eggs'},
    {id: '3', text: 'Bread'},
    {id: '4', text: 'Bagel'},
  ]);
  const deleteItem = (id) => {
    setItems(prevItems => {
      return prevItems.filter(item => item.id != id);
    });
  };

  const addItem = (text) => {
    setItems(prevItems => {
      return [{id: '5', text}, ...prevItems];
    });
  }

  return (
    <View style={styles.container}>
      <Header title="Shopping List" />
      <AddItem addItem={addItem} />
      <FlatList 
        data = {items}
        renderItem={({item}) => (
        <ListItem item={item} deleteItem={deleteItem} />
        )}
      />
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    paddingTop: 60,
  },
});

export default App;

components/AddItem.js

import React, {useState} from 'react';
import { View, Text, StyleSheet, TextInput, TouchableOpacity } from 'react-native';
import Icon from 'react-native-vector-icons/dist/FontAwesome'

const AddItem = ({title, addItem}) => {
    const [text, setText] = useState('');

    const onChange = (textValue) => setText(textValue);

    return (
        <View>
            <TextInput placeholder="Add Item..." style={styles.input} onChangeText={onChange} />
            <TouchableOpacity style={styles.btn} onPress={() => addItem(text)}>
                <Text style={styles.btnText}><Icon name="plus" size={20} />Add Item</Text>
            </TouchableOpacity>
        </View>
    );
};

const styles = StyleSheet.create({
    input: {
        height: 60,
        padding: 8,
        fontSize: 16,
    },
    btn: {
        backgroundColor: '#c2bad8',
        padding: 9,
        margin: 5,
    },
    btnText: {
        color: 'darkslateblue',
        fontSize: 20,
        textAlign: 'center',
    },
});

export default AddItem;

Adding an Alert

import React, {useState} from 'react';
import { View, Text, StyleSheet, FlatList, Alert } from 'react-native';
import Header from './components/Header';
import ListItem from './components/ListItem';
import AddItem from './components/AddItem';

const App = () => {
  const [items, setItems] = useState([
    {id: '1', text: 'Milk'},
    {id: '2', text: 'Eggs'},
    {id: '3', text: 'Bread'},
    {id: '4', text: 'Bagel'},
  ]);
  const deleteItem = (id) => {
    setItems(prevItems => {
      return prevItems.filter(item => item.id != id);
    });
  };

  const addItem = (text) => {
    if(!text) {
      Alert.alert('Error', 'Please enter an item', { text: 'Ok'})
    } else {
      setItems(prevItems => {
        return [{id: '5', text}, ...prevItems];
      });
    }
  }

  return (
    <View style={styles.container}>
      <Header title="Shopping List" />
      <AddItem addItem={addItem} />
      <FlatList 
        data = {items}
        renderItem={({item}) => (
        <ListItem item={item} deleteItem={deleteItem} />
        )}
      />
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    paddingTop: 60,
  },
});

export default App;
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