Javascript React Redux连接的组件不';状态更改后无法更新
我正在尝试使用React Redux。我遇到一种情况,一个连接的组件(Coordinates.jsx)嵌套在另一个连接的组件(Canvas.jsx)中 源代码(纱线安装,然后纱线启动) 在父组件Canvas.jsx中,我在componentDidMount()中调度一个操作,该操作不可变地更改状态 Canvas.jsxJavascript React Redux连接的组件不';状态更改后无法更新,javascript,reactjs,redux,react-redux,Javascript,Reactjs,Redux,React Redux,我正在尝试使用React Redux。我遇到一种情况,一个连接的组件(Coordinates.jsx)嵌套在另一个连接的组件(Canvas.jsx)中 源代码(纱线安装,然后纱线启动) 在父组件Canvas.jsx中,我在componentDidMount()中调度一个操作,该操作不可变地更改状态 Canvas.jsx componentDidMount(){ this.props.addCanvasSize(窗口宽度、窗口高度) } 问题是在更改状态后,子组件坐标.jsx不会得到更新,并且co
componentDidMount(){
this.props.addCanvasSize(窗口宽度、窗口高度)
}
问题是在更改状态后,子组件坐标.jsx不会得到更新,并且console.log显示未定义
Coordinates.jsx
componentDidMount(){
console.log(this.props.canvasSize)
}
我确信状态已正确更新(使用Redux devTool进行检查),并且我猜我没有在reduce中对状态进行变异
如果我在setTimeout中包装console.log(this.props.canvasSize),那么它将显示corect状态
index.js(商店)
减速器/reducer.js
export const addCanvasSizeAction = (windowWidth, windowHeight) => ({
type: 'ADD_CANVAS_SIZE',
windowWidth,
windowHeight
})
export const reducer = (state={}, action) => {
switch (action.type) {
case 'ADD_CANVAS_SIZE':
return Object.assign({}, state, {canvasSize: {canvasWidth: action.windowWidth, canvasHeight: action.windowHeight}})
default:
return state
}
}
const mapStateToProps = (state) => ({
state: state
})
const mapDispatchToProps = (dispatch) => ({
addCanvasSize: (windowWidth, windowHeight) =>
{dispatch(addCanvasSizeAction(windowWidth, windowHeight))}
})
const CanvasCont = connect(
mapStateToProps,
mapDispatchToProps
)(Canvas)
const mapStateToProps = (state) => ({
canvasSize: state.canvasSize
})
const mapDispatchToProps = (dispatch) => ({
})
const CoordinatesCont = connect(
mapStateToProps,
mapDispatchToProps
)(Coordinates)
组件/App.jsx
class App extends React.Component {
render() {
return (
<div>
<CanvasCont />
</div>
)
}
}
class Canvas extends React.Component {
constructor(props) {
super(props);
}
componentDidMount() {
var windowWidth = window.innerWidth-100;
var windowHeight = window.innerHeight-100;
var createCanvas = document.createElement("canvas");
createCanvas.id = 'canvas';
createCanvas.width = windowWidth;
createCanvas.height = windowHeight;
ReactDOM.findDOMNode(this).appendChild(createCanvas);
var rect = canvas.getBoundingClientRect();
var ctx = createCanvas.getContext('2d');
this.props.addCanvasSize(windowWidth, windowHeight)
}
render() {
return (<div>
<CoordinatesCont />
</div>)
}
}
class Coordinates extends React.Component {
constructor(props) {
super(props);
}
componentDidMount() {
console.log(this.props.canvasSize)
}
render() {
var inlineStyle={
width: "800px",
height: "600px"
}
return (
<div >
<span style={inlineStyle} onMouseMove={this.handleMouseMove}></span>
</div>
)
}
}
容器/CoordinatesCont.js
export const addCanvasSizeAction = (windowWidth, windowHeight) => ({
type: 'ADD_CANVAS_SIZE',
windowWidth,
windowHeight
})
export const reducer = (state={}, action) => {
switch (action.type) {
case 'ADD_CANVAS_SIZE':
return Object.assign({}, state, {canvasSize: {canvasWidth: action.windowWidth, canvasHeight: action.windowHeight}})
default:
return state
}
}
const mapStateToProps = (state) => ({
state: state
})
const mapDispatchToProps = (dispatch) => ({
addCanvasSize: (windowWidth, windowHeight) =>
{dispatch(addCanvasSizeAction(windowWidth, windowHeight))}
})
const CanvasCont = connect(
mapStateToProps,
mapDispatchToProps
)(Canvas)
const mapStateToProps = (state) => ({
canvasSize: state.canvasSize
})
const mapDispatchToProps = (dispatch) => ({
})
const CoordinatesCont = connect(
mapStateToProps,
mapDispatchToProps
)(Coordinates)
在处理父/子关系时,您应该记住,在对父级调用
组件didmount
之前,先对子级调用它(如本答案中所述)
实际上,在你的情况下,发生了以下情况:
组件didmount
回调,但状态尚未定义控制台.log
被触发,但道具中没有任何内容
组件didmount
并更新状态console.log
,则现在您的属性是最新的现在,如果您想解决这个问题,您需要使用
componentWillReceiveProps
回调,每当为组件提供新属性时,就会调用该回调 请将诊断潜在问题所需的代码放在帖子中,而不是指向外部存储库。它的连接方式很重要,状态形状很重要。我不知道孩子的组件didmount是第一个被调用的。谢谢你提供的信息,现在我知道会发生什么了。这意味着在这种情况下,更新子组件的唯一方法是检查nextProps,然后强制更新组件?是否有其他方法使组件保持最新状态?也许应用程序组件中的嵌套画布和坐标(我的意思是摆脱父/子关系?)。要确信一切都按预期工作,请尝试在子组件的渲染功能中添加console.log(this.props)
,您将看到(如果我是正确的)2个日志第一个日志是未定义的
,另一个日志具有正确的画布大小
value@GalaxyWanderer但这是有道理的,正确的?必须先装入组件的子组件,然后才能考虑装入父组件。