在Angular 2中的路线之间导航时显示加载屏幕-Java 学习之路

103

当我在Angular 2中更改路线时如何显示加载屏幕？

5 回答

当前的角度路由器提供导航事件 . 您可以订阅这些并相应地进行UI更改 . 请记住在其他事件（例如 NavigationCancel 和 NavigationError ）中计数以阻止您的微调器，以防路由器转换失败 .

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) {
    router.events.subscribe((event: RouterEvent) => {
      this.navigationInterceptor(event)
    })
  }

  // 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>

Performance Improved Answer ：如果您关心性能，那么有一种更好的方法，实施起来稍微繁琐，但性能提升值得额外工作 . 我们可以利用Angular的 NgZone 和 Renderer 来打开/关闭将绕过Angular 's change detection when we change the spinner'状态的微调器，而不是使用 *ngIf 来有条件地显示微调器 . 与使用 *ngIf 或 async 管道相比，我发现这可以使动画更流畅 .

这类似于我之前的回答和一些调整：

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((event: RouterEvent) => {
      this._navigationInterceptor(event)
    })
  }

  // 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>

回复于 2024-04-28T05:28:46+08:00

UPDATE:3 现在我已经升级到新的路由器，如果使用 CanDeactivate guard， @borislemke 的方法将无效 . 我贬低我的旧方法， ie: 这个答案

UPDATE2 ：新路由器中的路由器事件看起来很有希望the answer由 @borislemke 似乎涵盖了微调器实现的主要方面，我还没有测试它，但我推荐它 .

UPDATE1: 我在 Old-Router 的时代写了这个答案，当时曾经只有一个事件 route-changed 通过 router.subscribe() 通知 . 我也觉得下面的方法超载，并试图只使用 router.subscribe() ，它 backfired ，因为没有办法检测 canceled navigation . 所以我不得不回到冗长的方法（双重工作） .

如果您在Angular2中了解自己的方式，那么这就是您需要的

Boot.ts

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

bootstrap(MyApp, [SpinnerService]);

Root Component- (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 { }

Spinner-Component （将订阅Spinner-service以相应地更改活动的值）

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）

定义要由spinner-component订阅的observable以更改更改时的状态，并定义用于了解和设置微调器活动/非活动的函数 .

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;
  }
}

All Other Routes' Components

（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();
  }
}

回复于 2024-04-28T05:28:46+08:00

为什么不使用简单的CSS：

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

在你的风格：

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

或者甚至我们可以为第一个答案做到这一点：

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

然后就是这么简单

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

这里的技巧是，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选择器我们可以显示和隐藏加载 .

回复于 2024-04-28T05:28:46+08:00

如果您只有第一条路线需要特殊逻辑，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');
                   });

我需要隐藏我的页脚，否则会出现在页面顶部 . 此外，如果您只想要第一页的加载器，您可以使用它 .

回复于 2024-04-28T05:28:46+08:00

168

你也可以使用这个existing solution . 演示is here . 它看起来像youtube加载栏 . 我刚刚找到它并将其添加到我自己的项目中 .

回复于 2024-04-28T05:28:46+08:00

在Angular 2中的路线之间导航时显示加载屏幕

5 回答

AppComponent

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