Why does the QR Scanner Ionic plugin generate an error? - ios

Question

EDIT: I managed to make the plugin work, but when I test the app on my iPhone and click the button, Xcode sends me a warning: THREAD WARNING: ['QRScanner'] took '468.501953' ms. Plugin should use a background thread.
I tried so many things and follow so many articles and tutorials (also here, on SO) to get rid of this. I'm building an Ionic app, using the QR Scanner plugin that this framework provides. My app.module.ts is:
// Here are the basic Ionic import statements.
// Eventually, I import the plugin to scan QR codes.
import { QRScanner, QRScannerStatus } from '#ionic-native/qr-scanner';
#NgModule({
declarations: [ MyApp, HomePage ],
imports: [ BrowserModule, IonicModule.forRoot(MyApp) ],
bootstrap: [IonicApp],
entryComponents: [ MyApp, HomePage ],
providers: [ StatusBar, SplashScreen, QRScanner,
{provide: ErrorHandler, useClass: IonicErrorHandler}
]
})
export class AppModule { }
The folder structure is:
My app has only one page, HomePage, and the content of the src/pages/home/home.ts file is:
import { Component } from '#angular/core';
import { NavController } from 'ionic-angular';
import { QRScanner, QRScannerStatus } from '#ionic-native/qr-scanner';
#Component({
selector: 'page-home',
templateUrl: 'home.html'
})
export class HomePage {
constructor(public navCtrl: NavController, private qrScanner: QRScanner) { }
scanQrCode() {
this.qrScanner.prepare().then((status: QRScannerStatus) => {
if (status.authorized) {
let scanSub = this.qrScanner.scan().subscribe((text: string) => { console.log('Scanned something', text);
this.qrScanner.hide();
scanSub.unsubscribe();
});
} else if (status.denied) {
// ...
} else {
// ...
}
}).catch((e: any) => console.log('Error is', e));
}
}
Inside the src/pages/home/home.html file, I have:
<ion-header>
<ion-navbar>
<ion-title>
Ionic Blank
</ion-title>
</ion-navbar>
</ion-header>
<ion-content padding>
<button ion-button (click)="scanQrCode()"></button>
</ion-content>
I build the app and run it on my iPhone 5, but when I click the button to scan a code, Xcode sends this: Error is [Object object]. Do you know why?