为什么状态无法在React组件中重置？

Question

这是一种方法，您可以看到许多设置为export default class App extends React.Component { render() { return ( <View style={styles.container}> <TextInput style={styles.box}/> </View> ); }} const styles = StyleSheet.create({ container: { flex: 1, justifyContent: 'center', paddingTop: Constants.statusBarHeight, backgroundColor: '#ecf0f1', padding: 8, }, box: { margin: 24, fontSize: 18, fontWeight: 'bold', textAlign: 'center', backgroundColor: 'red' }, }); 的行，但是它们不起作用。

undefined

您会看到，值未重置：

我正在调试，但是它没有重置值，为什么？我想念什么吗？这是全班学生：

  handleDismissMenuAndLogOut = () => {
    this.setState({
      buyOrRelease: "buy",
      anchorEl: undefined,
      isLoggedIn: undefined,
      userID: undefined,
      name: undefined,
      email: undefined,
      picture: undefined
    }, this.props.userLoginAndDataDownloadCompletedOut(this.state));
  };

Answer 1

setState是异步的，这意味着直接在setState函数之后运行的代码将无法访问新状态。您必须使用setState的第二个参数来访问新状态。

  this.setState({
      isLoggedIn: false,
      name: "",
      buyOrRelease: "buy",
      anchorEl: undefined,
      isLoggedIn: undefined,
      userID: undefined,
      name: undefined,
      email: undefined,
      picture: undefined
  }, this.props.userLoginAndDataDownloadCompletedOut);

  this.setState({
      key: value,
      // This new state is shallow merged with the old one, if you dont specify an existing key, the existing key and value will remain the same.
  }, (newState) => {
      newState.key === value; // newState contains the new complete state.
  });