学习一个框架或库的最好方法是看官方文档，并着手去写例子。最近在利用空闲的时间学习angular，那今天就尝试写一个message组件，并通过message服务动态加载message组件。
我所参与的项目基本是用jquery完成的。之前，在项目中自己动手写过一个简单的message插件，样子如下图。

那现在就使用angular（版本5.0.0）来实现message组件。

message组件

message组件要根据传入的类型、消息和duration来显示。创建三个文件：message.component.ts,message.component.html,message.component.css，代码如下。

//message.component.tsimport {Component,Input,OnInit,ChangeDetectionStrategy} from '@angular/core';import { trigger, state, style, transition, animate } from '@angular/animations';const mapping={ success:'glyphicon-ok-sign', warning:'glyphicon-exclamation-sign', error:'glyphicon-exclamation-sign', info:'glyphicon-ok-circle'}@Component({ selector:'upc-ng-message', templateUrl:'./message.component.html', styleUrls:['./message.component.css'], changeDetection:ChangeDetectionStrategy.OnPush})export class MessageComponent implements OnInit{ ngOnInit(): void { this.typeClass=['upc-message-' + this.msgType]; this.typeIconClass=[mapping[this.msgType]]; } @Input() msgType:'success' | 'info' | 'warning' | 'error'='info' @Input() payload:string = '' private typeClass private typeIconClass}<!--*message.component.html--><div class="upc-message"> <div class="upc-message-content" [ngClass]="typeClass"> <i class="glyphicon" [ngClass]="typeIconClass"></i> {{payload}} </div></div>.upc-message { position: fixed; z-index: 1999; width: 100%; top: 36px; left: 0; pointer-events: none; padding: 8px; text-align: center; } .upc-message i { margin-right: 8px; font-size: 14px; top: 1px; position: relative; } .upc-message-success i { color: green; } .upc-message-warning i { color: yellow; } .upc-message-error i { color: red; } .upc-message-content { padding: 8px 16px; -ms-border-radius: 4px; border-radius: 4px; -webkit-box-shadow: 0 2px 8px #000000; -ms-box-shadow: 0 2px 8px #000000; box-shadow: 0 2px 8px #000000; box-shadow: 0 2px 8px rgba(0,0,0,.2); background: #fff; display: inline-block; pointer-events: all; }

ComponentLoader

通过官方文档动态组件一节，可以了解动态创建组件需要通过ComponentFactoryResolver来完成。使用ComponentFactoryResolver创建ComponentFactory，再通过ComponentFactory的create方法创建组件。看官方文档中API的说明，ComponentFactory的create方法至少需要一个injector参数，而injector的创建在文档中也有提到，其中参数providers为需要注入的类。再梳理下整个过程：

提供providers

创建Injector实例

创建ComponetFactory

使用ComponetFactory创建ComponentRef

//ComponentFactory的create方法create(injector: Injector, projectableNodes?: any[][], rootSelectorOrNode?: string|any, ngModule?: NgModuleRef<any>): ComponentRef<C>//使用Injector的create创建injector实例static create(providers: StaticProvider[], parent?: Injector): Injector

为了代码的复用，这里创建通用的loader类来完成组件的动态创建。其中，attch方法用于初始化ComponetFactory（参数为组件类型）；to方法用于标识组件的父容器；provider方法用于初始化可注入的类；create方法用于创建组件并手动变更检测；remove方法用于移除组件。

import { ComponentFactoryResolver, ComponentFactory, ComponentRef, Type, Injector, Provider, ElementRef} from '@angular/core';export class ComponentLoader<T>{ constructor(private _cfr: ComponentFactoryResolver, private _injector: Injector) { } private _componentFactory: ComponentFactory<T> attch(componentType: Type<T>): ComponentLoader<T> { this._componentFactory = this._cfr.resolveComponentFactory<T>(componentType); return this; } private _parent: Element to(parent: string | ElementRef): ComponentLoader<T> { if (parent instanceof ElementRef) { this._parent = parent.nativeElement; } else { this._parent = document.querySelector(parent); } return this; } private _providers: Provider[] = []; provider(provider: Provider) { this._providers.push(provider); } create(opts: {}): ComponentRef<T> { const injector = Injector.create(this._providers as any[], this._injector); const componentRef = this._componentFactory.create(injector); Object.assign(componentRef.instance, opts); if (this._parent) { this._parent.appendChild(componentRef.location.nativeElement); } componentRef.changeDetectorRef.markForCheck(); componentRef.changeDetectorRef.detectChanges(); return componentRef; } remove(ref:ComponentRef<T>){ if(this._parent){ this._parent.removeChild(ref.location.nativeElement) } ref=null; }}

同时，为了便于loader的创建，再创建LoaderFactory类，代码如下：

import { ComponentFactoryResolver, Injector, Injectable, ElementRef} from '@angular/core';import { ComponentLoader } from './component-loader.class';@Injectable()export class ComponentLoaderFactory { constructor(private _injector: Injector, private _cfr: ComponentFactoryResolver) { } create<T>(): ComponentLoader<T> { return new ComponentLoader(this._cfr, this._injector); }}

message service

message service提供显示message的API，代码如下：

import {Injectable,Injector} from '@angular/core';import { ComponentLoaderFactory } from '../component-loader/component-loader.factory';import {MessageComponent} from './message.component';import {ComponentLoader} from '../component-loader/component-loader.class';@Injectable()export class MessageService{ constructor(private _clf:ComponentLoaderFactory,private _injector:Injector){ this.loader=this._clf.create<MessageComponent>(); } private loader:ComponentLoader<MessageComponent> private createMessage(t,c,duration=2000){ this.loader.attch(MessageComponent).to('body'); const opts = { msgType: t, payload:c }; const ref = this.loader.create(opts); ref.changeDetectorRef.markForCheck(); ref.changeDetectorRef.detectChanges(); let self=this; let st = setTimeout(() => { self.loader.remove(ref); }, duration); } public info(payload,duration?) { this.createMessage('info',payload,duration); } public success(payload,duration?) { this.createMessage('success',payload,duration); } public error(payload,duration?) { this.createMessage('error',payload,duration); } public warning(payload,duration?) { this.createMessage('warning',payload,duration); }}

message.module

最后，增加message.module.ts。记得要把动态创建的组件添加到entryComponents数组中。

import {NgModule} from '@angular/core';import { CommonModule } from '@angular/common';import {MessageComponent} from './message.component';import {MessageService} from './message.service';import {ComponentLoaderFactory} from '../component-loader/component-loader.factory';@NgModule({ imports:[CommonModule], declarations:[MessageComponent], providers:[MessageService,ComponentLoaderFactory], entryComponents:[MessageComponent], exports:[MessageComponent]})export class MessageModule{}

使用方法

注入MessageService，调用API使用Message组件。

this._msgService.success('成功了!');

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。