运行报错 Can only update a mounted or mounting component. This usually means you called setState() on an unmounted component. This is a no-op. Please check the code for the undefined component.

内存泄漏，需要销毁

componentDidMount(){
this.timer=setInterval (
()=>{
let opacity = this.state.opacity;
opacity -= .05;
if (opacity < 0.1) {
opacity = 1.0;
}
this.setState({
opacity: opacity
});
},100)
}
componentWillUnmount() {
// 如果存在this.timer，则使用clearTimeout清空。
// 如果你使用多个timer，那么用多个变量，或者用个数组来保存引用，然后逐个clear
clearTimeout(this.timer);
}