我想执行一些基于窗口重新大小事件(在加载和动态)的任务。
目前我的DOM如下:
<div id="Harbour">
<div id="Port" (window:resize)="onResize($event)" >
<router-outlet></router-outlet>
</div>
</div>
事件正确触发
export class AppComponent {
onResize(event) {
console.log(event);
}
}
我如何从这个事件对象检索宽度和高度?
谢谢。
正确的方法是利用EventManager类来绑定事件。这让你的代码可以在其他平台上工作,例如使用Angular Universal进行服务器端渲染。
import { EventManager } from '@angular/platform-browser';
import { Observable } from 'rxjs/Observable';
import { Subject } from 'rxjs/Subject';
import { Injectable } from '@angular/core';
@Injectable()
export class ResizeService {
get onResize$(): Observable<Window> {
return this.resizeSubject.asObservable();
}
private resizeSubject: Subject<Window>;
constructor(private eventManager: EventManager) {
this.resizeSubject = new Subject();
this.eventManager.addGlobalEventListener('window', 'resize', this.onResize.bind(this));
}
private onResize(event: UIEvent) {
this.resizeSubject.next(<Window>event.target);
}
}
在组件中使用这个服务非常简单,只需将这个服务作为提供者添加到app.module中,然后在组件的构造函数中导入它。
import { Component, OnInit } from '@angular/core';
@Component({
selector: 'my-component',
template: ``,
styles: [``]
})
export class MyComponent implements OnInit {
private resizeSubscription: Subscription;
constructor(private resizeService: ResizeService) { }
ngOnInit() {
this.resizeSubscription = this.resizeService.onResize$
.subscribe(size => console.log(size));
}
ngOnDestroy() {
if (this.resizeSubscription) {
this.resizeSubscription.unsubscribe();
}
}
}
在angular CDK中有一个ViewportRuler服务。它在区域外运行,支持方向改变和大小调整。它也适用于服务器端渲染。
@Component({
selector: 'my-app',
template: `
<p>Viewport size: {{ width }} x {{ height }}</p>
`
})
export class AppComponent implements OnDestroy {
width: number;
height: number;
private readonly viewportChange = this.viewportRuler
.change(200)
.subscribe(() => this.ngZone.run(() => this.setSize()));
constructor(
private readonly viewportRuler: ViewportRuler,
private readonly ngZone: NgZone
) {
// Change happens well, on change. The first load is not a change, so we init the values here. (You can use `startWith` operator too.)
this.setSize();
}
// Never forget to unsubscribe!
ngOnDestroy() {
this.viewportChange.unsubscribe();
}
private setSize() {
const { width, height } = this.viewportRuler.getViewportSize();
this.width = width;
this.height = height;
}
}
ViewportRuler的Stackblitz示例
好处是,它限制了更改检测周期(它只会在区域中运行回调时触发),而(window:resize)将在每次调用时触发更改检测。
我还没看到有人在谈论angular/cdk的MediaMatcher。
您可以定义一个MediaQuery并将一个侦听器附加到它-然后在模板(或ts)上的任何地方,如果匹配了Matcher,就可以调用东西。
LiveExample
App.Component.ts
import {Component, ChangeDetectorRef} from '@angular/core';
import {MediaMatcher} from '@angular/cdk/layout';
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
mobileQuery: MediaQueryList;
constructor(changeDetectorRef: ChangeDetectorRef, media: MediaMatcher) {
this.mobileQuery = media.matchMedia('(max-width: 600px)');
this._mobileQueryListener = () => changeDetectorRef.detectChanges();
this.mobileQuery.addListener(this._mobileQueryListener);
}
private _mobileQueryListener: () => void;
ngOnDestroy() {
this.mobileQuery.removeListener(this._mobileQueryListener);
}
}
App.Component.Html
<div [class]="mobileQuery.matches ? 'text-red' : 'text-blue'"> I turn red on mobile mode
</div>
App.Component.css
.text-red {
color: red;
}
.text-blue {
color: blue;
}
来源:https://material.angular.io/components/sidenav/overview
这里有一个更好的方法。根据Birowsky的回答。
步骤1:用RxJS observable创建一个angular服务。
import { Injectable } from '@angular/core';
import { Observable, BehaviorSubject } from 'rxjs';
@Injectable()
export class WindowService {
height$: Observable<number>;
//create more Observables as and when needed for various properties
hello: string = "Hello";
constructor() {
let windowSize$ = new BehaviorSubject(getWindowSize());
this.height$ = (windowSize$.pluck('height') as Observable<number>).distinctUntilChanged();
Observable.fromEvent(window, 'resize')
.map(getWindowSize)
.subscribe(windowSize$);
}
}
function getWindowSize() {
return {
height: window.innerHeight
//you can sense other parameters here
};
};
步骤2:注入上述服务,并订阅在服务中创建的任何可观察对象,无论您希望在哪里接收窗口大小调整事件。
import { Component } from '@angular/core';
//import service
import { WindowService } from '../Services/window.service';
@Component({
selector: 'pm-app',
templateUrl: './componentTemplates/app.component.html',
providers: [WindowService]
})
export class AppComponent {
constructor(private windowService: WindowService) {
//subscribe to the window resize event
windowService.height$.subscribe((value:any) => {
//Do whatever you want with the value.
//You can also subscribe to other observables of the service
});
}
}
充分理解响应式编程总是有助于克服困难的问题。希望这能帮助到一些人。
<div (window:resize)="onResize($event)"
onResize(event) {
event.target.innerWidth;
}
或者使用HostListener装饰器:
@HostListener('window:resize', ['$event'])
onResize(event) {
event.target.innerWidth;
}
支持的全局目标有window、document和body。
在https://github.com/angular/angular/issues/13248在Angular中实现之前,强制订阅DOM事件并使用RXJS来减少事件的数量(如其他一些答案所示)会更好地提高性能。