ReactCSSTransitionGroup：为什么transitionAppear 不起作用？

我正在尝试使通知淡入/淡出，但它不起作用transitionAppear。我正在向事件添加一个元素（通知弹出窗口）onBlur（在我单击输入外部之后）。动画leave在此期间运行顺利，但在此期间它appear只是突然出现而没有transition. 最近在 React 中，不要发誓太多 :D

代码沙盒： https ://codesandbox.io/s/l26j10613q

PS
如果我添加-它有效ReactCSSTransitionGroup，但没有。alert.jsappearleave

alert.js:

export default class Alert extends Component {
  render() {
    const { icon, text } = this.props;
    let classNames = "cards-wrapper-alert";
    return (
     <div className={classNames}>
       <Card zIndex="2">
         <Icon icon={icon} eClass="alert-message-icon"/>
         <Label text={text} fw="fw-medium" fs="fs-14" fc="c-dark"/>
       </Card>
     </div>
    );
  }
}

alert.css:

.alert-appear {
  max-height: 0;
  overflow: hidden;
}

.alert-appear.alert-appear-active {
  max-height: 80px;
  transition: max-height 300ms ease-in-out;
}

.alert-leave {
  max-height: 80px;
}

.alert-leave.alert-leave-active {
  max-height: 0;
  overflow: hidden;
  transition: max-height 300ms ease-in-out;
}

input.js:

<ReactCSSTransitionGroup
  component={this.prepareComponentForAnimation}
  transitionName="alert"
  transitionEnter={false}
  transitionAppear={true}
  transitionAppearTimeout={400}
  transitionLeaveTimeout={400}>
  {this.state.alert ?
    React.cloneElement(this.props.children, {
      icon: this.state.icon,
      text: this.state.text
    })
  : null}
</ReactCSSTransitionGroup>

例子：