为什么当状态改变时反应不调用渲染? [英] Why react doesn't call render when state is changed?

问题描述

状态更改时，我无法自动重新渲染视图. 状态已更改，但未调用render().但是，当我调用this.forceUpdate()时，一切都很好，但是我认为这不是最好的解决方案. 有人可以帮我吗?

I have problem with automatically re-rendering view, when state is changed. State has been changed, but render() is not called. But when I call this.forceUpdate(), everything is ok, but I think that's not the best solution. Can someone help me with that ?

class TODOItems extends React.Component {

constructor() {
    super();

    this.loadItems();
}

loadItems() {
    this.state = {
        todos: Store.getItems()
    };
}

componentDidMount(){
    //this loads new items to this.state.todos, but render() is not called
    Store.addChangeListener(() => { this.loadItems(); this.forceUpdate(); });
}

componentWillUnmount(){
    Store.removeChangeListener(() => { this.loadItems(); });
}

render() {

    console.log("data changed, re-render");
    //...
}}

推荐答案

在声明初始状态时，应该在构造函数中使用this.state = {};(就像在loadItems()方法中一样).要更新项目时，请使用this.setState({}).例如:

You should be using this.state = {}; (like in your loadItems() method) from the constructor when you are declaring the initial state. When you want to update the items, use this.setState({}). For example:

constructor() {
    super();

    this.state = {
        todos: Store.getItems()
    };
}

reloadItems() {
    this.setState({
        todos: Store.getItems()
    });
}

并更新您的componentDidMount:

Store.addChangeListener(() => { this.reloadItems(); });

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