Angular 动态组件

实现步骤

• Directive
• HostComponent
• 动态组件
• AdService
• 配置AppModule
• 需要了解的概念

Directive

• 我们需要一个Directive来标记动态组件是在哪个容器组件内部进行渲染的。
• 这个Directive可以获取对容器组件的引用。
• 仅此而已。

import { Directive, ViewContainerRef } from '@angular/core';

@Directive({
  selector: '[appAd]',
})
export class AdDirective {
  constructor(public viewContainerRef: ViewContainerRef) { }
}

HostComponent

• 我们需要一个容器组件，所有动态组件都是在这个容器组件中创建，销毁，重新创建。。。
• 需要将动态组件需要展示的数据和动态组件进行绑定。

import { Component, Input, AfterViewInit, ViewChild, ComponentFactoryResolver, OnDestroy } from '@angular/core';

import { AdDirective } from './ad.directive';
import { AdItem }      from './ad-item';
import { AdComponent } from './ad.component';

@Component({
  selector: 'app-add-banner',
  template: `
              <div class="ad-banner">
                <h3>Advertisements</h3>
                <!-- hostElement 在此！ -->
                <ng-template appAd></ng-template>
              </div>
            `
})
export class AdBannerComponent implements AfterViewInit, OnDestroy {
  @Input() ads: AdItem[];
  currentAddIndex: number = -1;
  @ViewChild(AdDirective) adHost: AdDirective;
  subscription: any;
  interval: any;

  constructor(private componentFactoryResolver: ComponentFactoryResolver) { }

  // 在 view 初始化结束后才开始创建动态组件
  ngAfterViewInit() {
    this.loadComponent();
    this.getAds();
  }

  ngOnDestroy() {
    clearInterval(this.interval);
  }

  loadComponent() {
    this.currentAddIndex = (this.currentAddIndex + 1) % this.ads.length;
    let adItem = this.ads[this.currentAddIndex];

    // 这里使用了工厂模式。其实Angular对于模板中出现的每一个Component都会创建一个ComponentFactory。在创建销毁时
    // 实际上使用的是组件工厂来创建组件的新实例。
    let componentFactory = this.componentFactoryResolver.resolveComponentFactory(adItem.component);

    let viewContainerRef = this.adHost.viewContainerRef;
    viewContainerRef.clear();
    // 传入对应的组件工厂来创建新的组件，并保存新组建的引用。
    let componentRef = viewContainerRef.createComponent(componentFactory);
    // 绑定数据
    (<AdComponent>componentRef.instance).data = adItem.data;
  }

  getAds() {
    this.interval = setInterval(() => {
      this.loadComponent();
    }, 3000);
  }
}

// add-item.ts
import { Type } from '@angular/core';

export class AdItem {
  constructor(public component: Type<any>, public data: any) {}
}

// ad.component.ts
export interface AdComponent {
  data: any;
}

在AppComponent 中使用

// app.component.ts

import { Component, OnInit } from '@angular/core';

import { AdService }         from './ad.service';
import { AdItem }            from './ad-item';

@Component({
  selector: 'app-root',
  template: `
    <div>
      <app-add-banner [ads]="ads"></app-add-banner>
    </div>
  `
})
export class AppComponent implements OnInit {
  ads: AdItem[];

  constructor(private adService: AdService) {}

  ngOnInit() {
    this.ads = this.adService.getAds();
  }
}

创建动态组件

// hero-job-ad.component.ts
import { Component, Input } from '@angular/core';

import { AdComponent }      from './ad.component';

@Component({
  template: `
    <div class="job-ad">
      <h4>{{data.headline}}</h4>
      {{data.body}}
    </div>
  `
})
export class HeroJobAdComponent implements AdComponent {
  @Input() data: any;

}

// hero-profile.component.ts
import { Component, Input }  from '@angular/core';

import { AdComponent }       from './ad.component';

@Component({
  template: `
    <div class="hero-profile">
      <h3>Featured Hero Profile</h3>
      <h4>{{data.name}}</h4>
      <p>{{data.bio}}</p>

      <strong>Hire this hero today!</strong>
    </div>
  `
})
export class HeroProfileComponent implements AdComponent {
  @Input() data: any;
}

创建service

import { Injectable }           from '@angular/core';

import { HeroJobAdComponent }   from './hero-job-ad.component';
import { HeroProfileComponent } from './hero-profile.component';
import { AdItem }               from './ad-item';

@Injectable()
export class AdService {
  getAds() {
    return [
      new AdItem(HeroProfileComponent, {name: 'Bombasto', bio: 'Brave as they come'}),

      new AdItem(HeroProfileComponent, {name: 'Dr IQ', bio: 'Smart as they come'}),

      new AdItem(HeroJobAdComponent,   {headline: 'Hiring for several positions',
                                        body: 'Submit your resume today!'}),

      new AdItem(HeroJobAdComponent,   {headline: 'Openings in all departments',
                                        body: 'Apply today'}),
    ];
  }
}

配置 AppModule

// app.module.ts
import { BrowserModule }        from '@angular/platform-browser';
import { NgModule }             from '@angular/core';
import { AppComponent }         from './app.component';
import { HeroJobAdComponent }   from './hero-job-ad.component';
import { AdBannerComponent }    from './ad-banner.component';
import { HeroProfileComponent } from './hero-profile.component';
import { AdDirective }          from './ad.directive';
import { AdService }            from './ad.service';

@NgModule({
  imports: [ BrowserModule ],
  providers: [AdService],
  declarations: [ AppComponent,
                  AdBannerComponent,
                  HeroJobAdComponent,
                  HeroProfileComponent,
                  AdDirective ],
  // 注意这里，需要手动引入动态组件的class，放入 entryComponents数组中，这样
  // Angular才能为动态组件创建组件工厂。如果不写，Angular在模板中不会发现这两个组件的具体引用，
  // 可能在打包时将组件代码排除。
  entryComponents: [ HeroJobAdComponent, HeroProfileComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule {
  constructor() {}
}

ng serve

完成。

需要了解的概念

• ViewContainerRef
• ViewChild
• ComponentFactoryResolver
• ComponentFactory
• ComponentRef