在Angular 2中的路线之间导航时显示加载屏幕

在Angular 2中更改路线时如何显示加载屏幕？

当前的Angular Router提供导航事件。您可以订阅这些内容并相应地更改UI。请记住要计入其他事件，例如，NavigationCancel并NavigationError在路由器转换失败时停止旋转器。

app.component.ts-您的根组件

...
import {
  Router,
  // import as RouterEvent to avoid confusion with the DOM Event
  Event as RouterEvent,
  NavigationStart,
  NavigationEnd,
  NavigationCancel,
  NavigationError
} from '@angular/router'

@Component({})
export class AppComponent {

  // Sets initial value to true to show loading spinner on first load
  loading = true

  constructor(private router: Router) {
    this.router.events.subscribe((e : RouterEvent) => {
       this.navigationInterceptor(e);
     })
  }

  // Shows and hides the loading spinner during RouterEvent changes
  navigationInterceptor(event: RouterEvent): void {
    if (event instanceof NavigationStart) {
      this.loading = true
    }
    if (event instanceof NavigationEnd) {
      this.loading = false
    }

    // Set loading state to false in both of the below events to hide the spinner in case a request fails
    if (event instanceof NavigationCancel) {
      this.loading = false
    }
    if (event instanceof NavigationError) {
      this.loading = false
    }
  }
}

app.component.html-您的根视图

<div class="loading-overlay" *ngIf="loading">
    <!-- show something fancy here, here with Angular 2 Material's loading bar or circle -->
    <md-progress-bar mode="indeterminate"></md-progress-bar>
</div>

提高性能的答案：如果您关心性能，有更好的方法，则实现起来会有些繁琐，但是提高性能值得进行额外的工作。代替使用*ngIf有条件地显示微调器，我们可以利用Angular的功能NgZone并Renderer打开/关闭微调器，这将在我们更改微调器的状态时绕过Angular的更改检测。与使用*ngIf或async管道相比，我发现这可以使动画更流畅。

这与我以前的答案有些相似，但有一些调整：

app.component.ts-您的根组件

...
import {
  Router,
  // import as RouterEvent to avoid confusion with the DOM Event
  Event as RouterEvent,
  NavigationStart,
  NavigationEnd,
  NavigationCancel,
  NavigationError
} from '@angular/router'
import {NgZone, Renderer, ElementRef, ViewChild} from '@angular/core'


@Component({})
export class AppComponent {

  // Instead of holding a boolean value for whether the spinner
  // should show or not, we store a reference to the spinner element,
  // see template snippet below this script
  @ViewChild('spinnerElement')
  spinnerElement: ElementRef

  constructor(private router: Router,
              private ngZone: NgZone,
              private renderer: Renderer) {
    router.events.subscribe(this._navigationInterceptor)
  }

  // Shows and hides the loading spinner during RouterEvent changes
  private _navigationInterceptor(event: RouterEvent): void {
    if (event instanceof NavigationStart) {
      // We wanna run this function outside of Angular's zone to
      // bypass change detection
      this.ngZone.runOutsideAngular(() => {
        // For simplicity we are going to turn opacity on / off
        // you could add/remove a class for more advanced styling
        // and enter/leave animation of the spinner
        this.renderer.setElementStyle(
          this.spinnerElement.nativeElement,
          'opacity',
          '1'
        )
      })
    }
    if (event instanceof NavigationEnd) {
      this._hideSpinner()
    }
    // Set loading state to false in both of the below events to
    // hide the spinner in case a request fails
    if (event instanceof NavigationCancel) {
      this._hideSpinner()
    }
    if (event instanceof NavigationError) {
      this._hideSpinner()
    }
  }

  private _hideSpinner(): void {
    // We wanna run this function outside of Angular's zone to
    // bypass change detection,
    this.ngZone.runOutsideAngular(() => {
      // For simplicity we are going to turn opacity on / off
      // you could add/remove a class for more advanced styling
      // and enter/leave animation of the spinner
      this.renderer.setElementStyle(
        this.spinnerElement.nativeElement,
        'opacity',
        '0'
      )
    })
  }
}

app.component.html-您的根视图

<div class="loading-overlay" #spinnerElement style="opacity: 0;">
    <!-- md-spinner is short for <md-progress-circle mode="indeterminate"></md-progress-circle> -->
    <md-spinner></md-spinner>
</div>

更新：3现在我已经升级到新的路由器，如果您使用防护，@ borislemke的方法将不起作用CanDeactivate。我正在退化为我的旧方法，ie:这个答案

更新2：在新的路由器看好和路由器事件，答案由@borislemke似乎涵盖微调实施的主要方面，我havent't测试，但我推荐它。

UPDATE1：我在的时代写了这个答案Old-Router，当时过去只有一个事件route-changed通过router.subscribe()。我也感到下面的方法过于繁琐router.subscribe()，并尝试仅使用它来完成它，但事与愿违，因为无法检测到canceled navigation。所以我不得不回到冗长的方法（双重工作）。

如果您知道如何在Angular2中解决问题，这就是您所需要的

引导程序

import {bootstrap} from '@angular/platform-browser-dynamic';
import {MyApp} from 'path/to/MyApp-Component';
import { SpinnerService} from 'path/to/spinner-service';

bootstrap(MyApp, [SpinnerService]);

根组件-（MyApp）

import { Component } from '@angular/core';
import { SpinnerComponent} from 'path/to/spinner-component';
@Component({
  selector: 'my-app',
  directives: [SpinnerComponent],
  template: `
     <spinner-component></spinner-component>
     <router-outlet></router-outlet>
   `
})
export class MyApp { }

微调组件（将订阅Spinner-service以相应地更改active的值）

import {Component} from '@angular/core';
import { SpinnerService} from 'path/to/spinner-service';
@Component({
  selector: 'spinner-component',
  'template': '<div *ngIf="active" class="spinner loading"></div>'
})
export class SpinnerComponent {
  public active: boolean;

  public constructor(spinner: SpinnerService) {
    spinner.status.subscribe((status: boolean) => {
      this.active = status;
    });
  }
}

Spinner-Service（引导此服务）

定义微调器组件要订阅的可观察对象以更改更改状态，并具有知道和设置微调器活动/不活动的功能。

import {Injectable} from '@angular/core';
import {Subject} from 'rxjs/Subject';
import 'rxjs/add/operator/share';

@Injectable()
export class SpinnerService {
  public status: Subject<boolean> = new Subject();
  private _active: boolean = false;

  public get active(): boolean {
    return this._active;
  }

  public set active(v: boolean) {
    this._active = v;
    this.status.next(v);
  }

  public start(): void {
    this.active = true;
  }

  public stop(): void {
    this.active = false;
  }
}

所有其他路线的组成部分

（样品）：

import { Component} from '@angular/core';
import { SpinnerService} from 'path/to/spinner-service';
@Component({
   template: `<div *ngIf="!spinner.active" id="container">Nothing is Loading Now</div>`
})
export class SampleComponent {

  constructor(public spinner: SpinnerService){} 

  ngOnInit(){
    this.spinner.stop(); // or do it on some other event eg: when xmlhttp request completes loading data for the component
  }

  ngOnDestroy(){
    this.spinner.start();
  }
}

为什么不只使用简单的CSS：

<router-outlet></router-outlet>
<div class="loading"></div>

并按照您的风格：

div.loading{
    height: 100px;
    background-color: red;
    display: none;
}
router-outlet + div.loading{
    display: block;
}

甚至我们可以为第一个答案这样做：

<router-outlet></router-outlet>
<spinner-component></spinner-component>

然后只是

spinner-component{
   display:none;
}
router-outlet + spinner-component{
    display: block;
}

这里的窍门是，新的路由和组件将始终出现在router-outlet之后，因此使用简单的CSS选择器就可以显示和隐藏负载。

如果只有第一条路线需要特殊的逻辑，则可以执行以下操作：

AppComponent

    loaded = false;

    constructor(private router: Router....) {
       router.events.pipe(filter(e => e instanceof NavigationEnd), take(1))
                    .subscribe((e) => {
                       this.loaded = true;
                       alert('loaded - this fires only once');
                   });

我需要隐藏我的页面页脚，否则该页脚将显示在页面顶部。另外，如果您只想为第一页加载程序，则可以使用它。

您也可以使用此现有解决方案。演示在这里。看起来就像youtube加载栏。我刚刚找到它并将其添加到我自己的项目中。