Ionic: How to not stack multiple toast notifications?

Question

I got the following Ionic code fragment for displaying alarms / errors in an industrial App:

showError(message: string) {
  let toast = this.toastController.create({
      message: message,
      position: 'top',
      duration: 5000,
      cssClass: 'danger',
      showCloseButton: true
  });
  toast.present();
}

The App triggers the error message every time it detects a connection issues, which will be also roughly on a 5 second timer.

Multiple calls to this method will lead to 2 or more error messages shown on top of each other if the timing of this code is changed. Can I somehow detect that a toast is already being displayed? Also then, the 5000 msec timer would not be necessary and I can just remove the error message again when the connection is re-established.

Thanks and BR Florian

Answer 1

You could store your Toast object in a variable outside your function, and call the dismiss() method before showing the next toast :

Ionic 4

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


toast: HTMLIonToastElement;    

showError(message: string) {
    try {
        this.toast.dismiss();
    } catch(e) {}

    this.toast = this.toastController.create({
        message: message,
        position: 'top',
        duration: 5000,
        color: 'danger',
        showCloseButton: true
    });
    toast.present();
}

Ionic 3

import { ToastController, Toast } from 'ionic-angular';


toast: Toast;    

showError(message: string) {
    try {
        this.toast.dismiss();
    } catch(e) {}

    this.toast = this.toastController.create({
        message: message,
        position: 'top',
        duration: 5000,
        cssClass: 'danger',
        showCloseButton: true
    });
    toast.present();
}

Answer 2

Here my solution :-)

// ToastService.ts
import { Injectable } from '@angular/core';
import { ToastController, Toast } from 'ionic-angular';

@Injectable()
export class ToastService {

  private toasts: Toast[] = [];

  constructor(private toastCtrl: ToastController) {}

  push(msg) {
    let toast = this.toastCtrl.create({
      message: msg,
      duration: 1500,
      position: 'bottom'
    });

    toast.onDidDismiss(() => {
      this.toasts.shift()
      if (this.toasts.length > 0) {
        this.show()
      }
    })

    this.toasts.push(toast)

    if (this.toasts.length === 1) {
      this.show()
    }
  }

  show() {
    this.toasts[0].present();
  }

}

Answer 3

I had troubles using all of the answer pre-aug 20. The toast would still present multiple times. Fixed it as simple as checking and setting a boolean value to proceed or to not proceed. By setting it directly to true, it won't run multiple times.

isToastPresent = false;

async presentToast(message: string, color?: Colors, header?: string): Promise<void> {
  if (!this.isToastPresent) {
    this.isToastPresent = true;

    const toast = await this.toastController.create({
      message: message,
      header: header || undefined,
      duration: 3500,
      position: 'top',
      color: color || Colors.dark,
    });

    toast.present();

    toast.onDidDismiss().then(() => (this.isToastPresent = false));
  }
}