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。
success.jpg
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.ts
import {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
}
{{payload}}
.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): ComponentRef
//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{
constructor(private _cfr: ComponentFactoryResolver,
private _injector: Injector) {
}
private _componentFactory: ComponentFactory
attch(componentType: Type): ComponentLoader {
this._componentFactory = this._cfr.resolveComponentFactory(componentType);
return this;
}
private _parent: Element
to(parent: string | ElementRef): ComponentLoader {
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 {
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){
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(): ComponentLoader {
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();
}
private loader:ComponentLoader
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);
st = null；
}, 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!');