CSS: Position loading indicator in the center of the screen

use position:fixed instead of position:absolute

The first one is relative to your screen window. (not affected by scrolling)

The second one is relative to the page. (affected by scrolling)

Note : IE6 doesn't support position:fixed.


This is what I've done for Angular 4:

<style type="text/css">  
  .centered {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    transform: -webkit-translate(-50%, -50%);
    transform: -moz-translate(-50%, -50%);
    transform: -ms-translate(-50%, -50%);
    color:darkred;
  }
</style>

</head>

<body>
  <app-root>
        <div class="centered">
          <h1>Loading...</h1>
        </div>
  </app-root>
</body>

Here is a solution using an overlay that inhibits along with material design spinner that you configure one time in your app and you can call it from anywhere.

app.component.html

(put this somewhere at the root level of your html)

<div class="overlay" [style.height.px]="height" [style.width.px]="width" *ngIf="message.plzWait$ | async">
        <mat-spinner class="plzWait"  mode="indeterminate"></mat-spinner>
</div>

app.component.css

.plzWait{
  position: relative;
  left: calc(50% - 50px);
  top:50%;

}
.overlay{
  position: absolute;
  top:0px;
  left:0px;
  width: 100%;
  height: 100%;
  background: black;
  opacity: .5;
  z-index: 999999;
}

app.component.ts

height = 0;
width = 0;
constructor(
    private message: MessagingService
  }
ngOnInit() {
    this.height = document.body.clientHeight;
    this.width = document.body.clientWidth;
  }

messaging.service.ts

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

@Injectable({
    providedIn: 'root',
  })
export class MessagingService {
    // Observable string sources
  private plzWaitObservable = new Subject<boolean>();


  // Public Observables you subscribe to
  public plzWait$ = this.plzWaitObservable.asObservable();

  public plzWait = (wait: boolean) => this.plzWaitObservable.next(wait);
}

Some other component

constructor(private message: MessagingService) { }
somefunction() {
    this.message.plzWait(true);
    setTimeout(() => {
            this.message.plzWait(false);
    }, 5000);
}

.loader{
  position: fixed;
  left: 0px;
  top: 0px;
  width: 100%;
  height: 100%;
  z-index: 9999;
  background: url('//upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Phi_fenomeni.gif/50px-Phi_fenomeni.gif') 
              50% 50% no-repeat rgb(249,249,249);
}
<div class="loader"></div>