Saving list with AsyncStorage

Question

So I made a "notepad" app and I want to do so the text that the user wrote etc it should be saved, so the text doesn't get reset when user quits the app.

I'm new to react-native, after a few google searches I need AsyncStorage? to make this happen. but really dunno on how to do it.

import React, { useState } from 'react';
import { 
StyleSheet, 
Text, 
View, 
FlatList, 
TouchableWithoutFeedback, 
TouchableOpacity,
Keyboard,
AsyncStorage
} from 'react-native';
import Header from './components/header';
import ListItem from './components/listitem';
import AddList from './components/addlist';

export default function App() {

    const [todos, setTodos] = useState([

    ]);

    const pressHandler = (key) => {
      setTodos((prevTodos) => {
      return prevTodos.filter(todo => todo.key != key);
     });
    }

    const submitHandler = (text) => {
      if(text.length > 0) {
        setTodos((prevTodos) => {
        return [
       { text: text, key: Math.random().toString() },
      ...prevTodos
     ];
   })
   } 
  }

 return (
  <TouchableWithoutFeedback onPress={() => {
    Keyboard.dismiss();
   }}>
  <View style={styles.container}>
    <Header />
     <View style={styles.content}>
      <AddList  submitHandler={submitHandler} />
       <View style={styles.todoList}>
        <FlatList 
          data={todos}
            renderItem={({ item }) => (
            <ListItem item={item} pressHandler={pressHandler} />
           )}
        />
      </View>
     </View>
   </View>
 </TouchableWithoutFeedback>
  );
  }

new problem out of nowhere worked great before now broken without touching the code

    const pressHandler = key =>
      setTodos(prevTodos => {
       const newTodos = prevTodos.filter(todo => todo.key !== key);

      storeTodosInAsync(newTodos);

      console.log(prevTodos);
    return newTodos;

    });


const submitHandler = text => {
  if (text.length > 0) {
      const key = Math.random().toString();
        setTodos(prevTodos => {
        const newTodos = [{ text, key }, ...prevTodos];

        storeTodosInAsync(newTodos);
        console.log(newTodos);
        return newTodos;
     });
   }
 };

Answer 1

You can use AsyncStorage to store and load data to/from local storage. One thing to note is data MUST be a string, so anything like an object that is not a string needs to be stringified. You can use JSON.stringify(...) to do this. And then when you get the string back you can use JSON.parse(...) to convert it back into an object.

So to convert your current code into something that automatically loads saved todos and always saves the latest, you could write this:

    import React, { useState, useEffect } from 'react';
    import {
      StyleSheet,
      Text,
      View,
      FlatList,
      TouchableWithoutFeedback,
      TouchableOpacity,
      Keyboard,
      AsyncStorage,
      Button
    } from 'react-native';
    import Header from './components/header';
    import ListItem from './components/listitem';
    import AddList from './components/addlist';
    
    export default function App() {
      const [todos, setTodos] = useState([]);
    
      useEffect(() => {
        restoreTodosFromAsync();
      }, []);
    
      const pressHandler = key => {
        console.log('Todos BEFORE delete');
        console.log(todos);
    
        const newTodos = todos.filter(todo => todo.key !== key);
    
        console.log('Todos AFTER delete');
        console.log(todos);
    
        setTodos(newTodos);
        storeTodosInAsync(newTodos);
      };
    
      const submitHandler = text => {
        if (text.length === 0) return;
    
        const key = Math.random().toString();
    
        console.log('Todos BEFORE submit');
        console.log(todos);
    
        const newTodos = [{ text, key }, ...todos];
    
        console.log('Todos AFTER submit');
        console.log(todos);
    
        setTodos(newTodos);
        storeTodosInAsync(newTodos);
      };
    
      const asyncStorageKey = '@todos';
    
      const storeTodosInAsync = newTodos => {
        const stringifiedTodos = JSON.stringify(newTodos);
    
        AsyncStorage.setItem(asyncStorageKey, stringifiedTodos).catch(err => {
          console.warn('Error storing todos in Async');
          console.warn(err);
        });
      };
    
      const restoreTodosFromAsync = () => {
        AsyncStorage.getItem(asyncStorageKey)
          .then(stringifiedTodos => {
            console.log('Restored Todos:');
            console.log(stringifiedTodos);
    
            const parsedTodos = JSON.parse(stringifiedTodos);
    
            if (!parsedTodos || typeof parsedTodos !== 'object') return;
    
            setTodos(parsedTodos);
          })
          .catch(err => {
            console.warn('Error restoring todos from async');
            console.warn(err);
          });
      };
    
      return (
        <TouchableWithoutFeedback onPress={Keyboard.dismiss}>
          <View style={styles.container}>
            <Header />
            <View style={styles.content}>
              <AddList submitHandler={submitHandler} />
              <View style={styles.todoList}>
                <FlatList
                  data={todos}
                  renderItem={({ item }) => <ListItem item={item} pressHandler={pressHandler} />}
                />
              </View>
            </View>
          </View>
        </TouchableWithoutFeedback>
      );
    }