How to dismiss Loader after data is ready

问题:

In my Ionic 2 app, I have a component that consumes a service which makes an http GET to fetch some data. My component then calls this service and when data is available it sets and presents it.

It looks like following:

export class FarmList implements OnInit {

  items: Object;


  constructor(public testService: TestService, public nav: NavController){
  }

  ngOnInit(){

    this.getData()
  }

  getData(){

    let loading = Loading.create({
      content: 'Please wait..',
      spinner: 'crescent'
    })

    this.nav.present(loading)

    this.testService.fetchData().then(data => this.items = data)

  }
...

}

While my component fetches the data asynchronously, I am trying to have a loader spinning and once the data is available, I want the loader to disappear.

However, with my current code the spinner keeps spinning even after data is available and displayed as can be seen the screenshot:

getData() is the method that makes service call. How can I fix this? Is it the correct way to implement loader?

回答1:

You can find a working plunker here.

Like you can see in the code of that plunker, I would make a few changes in order to make your code work properly:

  export class FarmList implements OnInit {

  items: Object;

  // Define the loading var here, so we can access later when the information is ready
  loading : any;

  constructor(public testService: TestService, public nav: NavController){
  }

  // Instead of 'ngOnInit', I would use 'ionViewWillEnter'
  ionViewWillEnter(){
    this.getData()
  }

  getData(){

    this.loading = Loading.create({
      content: 'Please wait..',
      spinner: 'crescent'
    })

    this.nav.present(this.loading)

    this.testService.fetchData().then(data => { 
                                       this.items = data;

                                       // After we get the data, we hide the loading
                                       this.hideLoading()});

  }

  // I 've added this method so we can grab the loading var and use it 
  // to hide the loading component.
  private hideLoading(){
    this.loading.dismiss();
  }
...

}

================================

UPDATE:

As of the release of Ionic 2.0.0-beta.8 (2016-06-06) changelog:

onPageWillEnter was renamed to ionViewWillEnter

回答2:

Following code works for me:

  async someFunction() {

    const loader = await this.loading.create({
      message: 'Loading...',
    });

    loader.present().then(() => {               // show loader
      this._someService.getData().subscribe(result => {

      },
        error => {
          console.log(error);
        });

      loader.dismiss();                         // dismiss loader
    });
  }

回答3:

ionic 4 - How to implement loading functionality:

import { LoadingController } from '@ionic/angular';

private timeoutTime = 10000;

async showLoading(){
        let loading = await this.loadingController.create({
            message: "Loading...",
            spinner: "bubbles"
        });
        loading.present();

        setTimeout(() => {
            loading.dismiss();  
        }, this.timeoutTime);
}

fetchProducts(){
        this.showLoading();

        this.productService.getProductsList().subscribe(res => {
            this.timeoutTime = 600; //dismiss loading bar after given seconds

            this.productsList = res['data'];

        });
}

I have implemented in my 2-3 projects. It works. BTW in this case i do not need to write below code in every function,

let loading = await this.loadingController.create({
            message: "Loading...",
            spinner: "bubbles"
        });
loading.present();

just call

this.showloading()

function before execution and call

this.timeoutTime = 600; 

at the time of execution completion