<aside class="hover-tip-wrapper">
 <span>{{tipText}}</span>
</aside>

import { Component, OnInit } from '@angular/core';
@Component({
 selector: 'app-hovertip',
 templateUrl: './hovertip.component.html',
 styleUrls: ['./hovertip.component.scss']
})
export class HovertipComponent implements OnInit {
 public tipText: string;
 constructor() { }
 ngOnInit() {
 }
}

.hover-tip-wrapper{
 width: max-content;
 position: absolute;
 height: 30px;
 line-height: 30px;
 bottom: calc(100% + 5px);
 right: calc( -10px - 100%);
 background-color: rgba(#000000,.8);
 padding: 0 5px;
 border-radius: 3px;
 &::after{
 content: '';
 position: absolute;
 height: 0;
 width: 0;
 border: 4px solid transparent;
 border-top-color: rgba(#000000,.8);
 left: 10px;
 top: 100%;
 }
 span {
 color: #ccc;
 font-size: 12px;
 }
}

entryComponents: [HovertipComponent],
declarations: [HovertipComponent, HovertipDirective]

import { Input , Directive , ViewContainerRef , ComponentRef, ComponentFactory, HostListener , ComponentFactoryResolver} from '@angular/core';
import { HovertipComponent } from './hovertip.component';
@Directive({
 selector: '[appHovertip]'
})
export class HovertipDirective {
 public hovertip: ComponentRef<HovertipComponent>;
 public factory: ComponentFactory<HovertipComponent>;
 constructor(
 private viewContainer: ViewContainerRef,
 private resolver: ComponentFactoryResolver
 ) {
 // 获取对应的组件工厂
 this.factory = this.resolver.resolveComponentFactory(HovertipComponent);
 }
 @Input('appHovertip') tipText: string;
　
 // 绑定鼠标移入的事件
 @HostListener('mouseenter') onmouseenter() {
　　 // 清空所有的view 
　　 this.viewContainer.clear();
 // 创建组件
 this.hovertip = this.viewContainer.createComponent(this.factory);
 // 向组件实例传递参数
 this.hovertip.instance.tipText = this.tipText;
 }
　
　// 绑定鼠标移出时的事件
 @HostListener('mouseleave') onmouseleave() {
 if (this.hovertip) {
　　// 组件销毁
 this.hovertip.destroy();
 }
 }
}