The loading spinner isn't appearing while the function is running

Question

The loading spinner isn't appearing while the function is running

Having trouble displaying a loading spinner while a function is running. I've tried different methods, but the spinner just won't appear.

Here's the HTML snippet:

<div class="row pt-3" id="firstRow">
 <div class="col">
  <button class="btn btn-dark back-button">
   <fa name="upload"></fa>
   <span>Load .csv file</span>
  </button>
  <input type="file" #fileImportInput name="File Upload" class="txtFileUpload p-3" (change)="fileChangeListener($event)" accept=".csv" />
    <img class="spinner" *ngIf="loading" src="../../../assets/img/gif-spinner/Spin-2s-200px.gif" />
 </div>
</div>

This is part of the TypeScript code:

export class MotionAnalysisComponent implements OnInit {
loading = false;

 fileChangeListener($event: any): void {
   this.loading = true;

   let files = $event.srcElement.files;

   if (this.isCSVFile(files[0])) {
    let input = $event.target;
    let reader = new FileReader();
    reader.readAsText(input.files[0]);

    reader.onload = () => {
     let csvData = reader.result;
     let csvRecordsArray = (<string>csvData).split(/\r\n|\n/);
     this.csvRecords = this.getDataRecordsArrayFromCSVFile(csvRecordsArray, 4);
   };

   reader.onerror = function () {
    alert('Unable to read ' + input.files[0]);
   };
  } else {
    alert("Please import valid .csv file.");
    this.fileReset();
  }

   this.loading = false;

If I remove the "this.loading = false" line within the function, the spinner appears after the function has finished executing and stays visible. How can I instruct the HTML to display the spinner during the function execution?

javascript angular typescript

Answer 1

Answer №1

In order to give the spinner enough time to initialize, you should execute the code asynchronously after marking loading as true. This can be accomplished by enclosing the code within a setTimeout callback function. Remember to reset the loading property at the end of this callback.

fileChangeListener($event) {
  this.loading = true;                    // Start by setting loading to true
  setTimeout(() => {                      // Utilize setTimeout for asynchronous execution
    let files = $event.srcElement.files;
    if (this.isCSVFile(files[0])) {
      ...
    } else {
      ...
    }
    this.loading = false;                 // Reset loading before exiting the callback
  }, 0);
}

For a demonstration, check out this stackblitz. Adjust the delay in setTimeout accordingly based on your specific needs (the example sets it to 0 ms).

Answer 2

In order to give the spinner enough time to initialize, you should execute the code asynchronously after marking loading as true. This can be accomplished by enclosing the code within a setTimeout callback function. Remember to reset the loading property at the end of this callback.

fileChangeListener($event) {
  this.loading = true;                    // Start by setting loading to true
  setTimeout(() => {                      // Utilize setTimeout for asynchronous execution
    let files = $event.srcElement.files;
    if (this.isCSVFile(files[0])) {
      ...
    } else {
      ...
    }
    this.loading = false;                 // Reset loading before exiting the callback
  }, 0);
}

For a demonstration, check out this stackblitz. Adjust the delay in setTimeout accordingly based on your specific needs (the example sets it to 0 ms).

Answer 3

Answer №2

My assumption is that

... a different section of the function...

represents a call to an observable or an asynchronous function, causing your

this.loading = false;

to be triggered immediately.

Without having full clarity on the content within that code block, it seems probable that you require a callback function that will execute once the asynchronous call has completed in order to properly set loading to false.

Answer 4

My assumption is that

... a different section of the function...

represents a call to an observable or an asynchronous function, causing your

this.loading = false;

to be triggered immediately.

Without having full clarity on the content within that code block, it seems probable that you require a callback function that will execute once the asynchronous call has completed in order to properly set loading to false.

Answer 5

Answer №3

@Component({
  selector: 'm-selector',
  templateUrl: './selector.component.html',
  changeDetection: ChangeDetectionStrategy.OnPush, <-- include this line
  styleUrls: ['./selector.component.scss']
})

implement a change detection method

next, within your constructor

constructor(
...,
private ref: ChangeDetectorRef <-- add this line
){ }

this allows you to manually request Angular to check for changes

you can then utilize it, like so:

this.loading = true
this.ref.markForCheck()

remember to call ref.markForCheck whenever you modify a variable impacting your HTML with *ngIf

this approach helps in reducing memory consumption by not constantly monitoring a specific variable

however, if your variable frequently changes, employing a listener is recommended

Answer 6

@Component({
  selector: 'm-selector',
  templateUrl: './selector.component.html',
  changeDetection: ChangeDetectionStrategy.OnPush, <-- include this line
  styleUrls: ['./selector.component.scss']
})

implement a change detection method

next, within your constructor

constructor(
...,
private ref: ChangeDetectorRef <-- add this line
){ }

this allows you to manually request Angular to check for changes

you can then utilize it, like so:

this.loading = true
this.ref.markForCheck()

remember to call ref.markForCheck whenever you modify a variable impacting your HTML with *ngIf

this approach helps in reducing memory consumption by not constantly monitoring a specific variable

however, if your variable frequently changes, employing a listener is recommended

Answer 7

Answer №4

To view debug information, it appears necessary to display the value of loading in your HTML:

Load .csv file

<p>loading {{ loading  }} </p>

<img class="spinner" *ngIf="loading" 
    src="../../../assets/img/gif-spinner/Spin-2s-200px.gif" />
</div>

If you notice that the value of loading updates correctly, then attempt to adjust the style accordingly:

img { 
     width: inherit; 
     height: inherit; 
     position: fixed; 
     top:0; 
     left:0; 
}

Could there be a typo? Your closing div tag seems to be incorrect: /div>

UPDATE:

Try setting the src attribute of the image using a template expression:

HTML:

<img class="spinner" 
     *ngIf="loading" 
     [src]="imagePath"/>

TypeScript:

imagePath = '../../../assets/img/gif-spinner/Spin-2s-200px.gif;'

Answer 8

To view debug information, it appears necessary to display the value of loading in your HTML:

Load .csv file

<p>loading {{ loading  }} </p>

<img class="spinner" *ngIf="loading" 
    src="../../../assets/img/gif-spinner/Spin-2s-200px.gif" />
</div>

If you notice that the value of loading updates correctly, then attempt to adjust the style accordingly:

img { 
     width: inherit; 
     height: inherit; 
     position: fixed; 
     top:0; 
     left:0; 
}

Could there be a typo? Your closing div tag seems to be incorrect: /div>

UPDATE:

Try setting the src attribute of the image using a template expression:

HTML:

<img class="spinner" 
     *ngIf="loading" 
     [src]="imagePath"/>

TypeScript:

imagePath = '../../../assets/img/gif-spinner/Spin-2s-200px.gif;'

The loading spinner isn't appearing while the function is running

Here's the HTML snippet:

This is part of the TypeScript code:

Answer №1

Answer №2

Answer №3

Answer №4

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