在 React 中重新加载页面时无法处理复选框的 state

Question

I'm trying to make a todo list app by using React and Material UI. Everything works fine except checkbox state. I'm saving each todo as object in todo list array in local storage as below.

• todoList is the state that I store each todo.
• isCompleted also a state with default boolean value of false

 let arr = todoList;
 const newTodo = new TodoItem({
                id: randomID,
                text: text,
                date: date,
                status: isCompleted
            });

 setTodoList([newTodo, ...arr]);
            localStorage.setItem('todos', JSON.stringify(todoList));

In another component I get saved items from local storage by useEffect and render them as todo list. I'm trying to get stored items every time isCompleted changes.

 useEffect(() => {
        let savedItem = JSON.parse(localStorage.getItem('todos'))
        if (savedItem !== null) {
            setTodoList(savedItem);
        }
    }, [isCompleted])

• This is the checkbox that should change read status.

  <FormControlLabel
       control={
       <Checkbox
       onChange={(e) => changeStatus(e.target.checked,index)}
       color="primary"
        />
       }
  />

• This is the function supposed to change status. Click handler works fine, it changes status with each click. However, the problem is when I refresh the page, checkbox resets itself to empty state even though status of todo completed in local storage.

 const changeStatus = (val,num) => {

        let item = todoList[num];
        if(val === false){
            setIsCompleted(true);
            item.status = isCompleted;

        }else if(val === true){
            setIsCompleted(false);
            item.status = isCompleted;
        }
        
        let storedItems = [...todoList];
        itemsToRender = storedItems;
        storedItems = storedItems.map(todo => todo.id === item.id ? todo = item : todo)
        console.log('STORED',storedItems);
        localStorage.setItem('todos', JSON.stringify(storedItems));
    }

• note that I'm mapping itemsToRender array to display todos in the component.

How can I prevent checkbox to reset itself(unchecked), I need checkbox to stay checked after reloading the page.

To me, I'm doing something wrong with useEffect or MUI checkbox component.

Thanks in advance for any help or advice.

Answer 1

You need to make the checkbox a controlled input by specifying the value attribute on it. And set the value attribute equal to the todo.status

todoList.map(todo => 
    (<FormControlLabel
        control={
            <Checkbox
               onChange={(e) => changeStatus(e.target.checked,index)}
               color="primary"
               value={todo.status}
            />
        }
    />)
)