Ionic V3 app looses focus after Keyboard appearance

Ionic Framework ionic-v3
1

Hi

I have an Ionic app using ionic v3, In the login page when i input wrong username and password the application div or input looses focus. its like the keyboard hide and leaves the keyboard space.I tried following the link setting-focus-to-an-input-in-ionic but didnt work. see code my below:

 class LoginPage {
    isEnabled: boolean = false;
    public usercreds: Credentials = {
        username: '',
        password: '',
    };

    @ViewChild('username') inputUsername: any;
    @ViewChild('password') inputPassword: any;

    constructor(
        public navCtrl: NavController,
        public firebaseAnalytics: FirebaseAnalytics,
        public alertCtrl: AlertController,
        public loadingCtrl: LoadingController,
        private auth: AuthService,
        private navParams: NavParams,
        platform: Platform,
    ) {
        this.firebaseAnalytics
            .logEvent('page_view', { page: 'Login' })
            .then((res: any) => console.log(res))
            .catch((error: any) => console.error(error));

        if (this.navParams.get('Logout')) {
            this.auth
                .Logout()
                .then(() => {
                    this.navCtrl.setRoot(LandingPage);
                })
                .catch();
        } else {
            this.auth
                .isLoggedIn()
                .then(isLoggedIn => {
                    if (isLoggedIn) {
                        this.navCtrl.setRoot(HomePage);
                    }
                })
                .catch();
        }
        const page: this = this;
        platform.registerBackButtonAction(() => {
            page.goToLanding();
        });
    }

    ionViewLoaded(): void {
        setTimeout(() => {
            this.inputUsername.setFocus();
            this.inputPassword.setFocus();
        }, 150);
    }

    public async login(user: Credentials): Promise<void> {
        this.response = '';
        this.inputUsername.setFocus();
        this.inputPassword.setFocus();
        const loadingCtrl: Loading = this.loadingCtrl.create({
            content: 'logging in, please wait...',
        });
        try {
            this.isEnabled = true;
            loadingCtrl.present();
            await this.auth.Login(user.username, user.password);
            loadingCtrl.dismiss();
            this.isEnabled = false;
            this.navCtrl.setRoot(ImpactPage);
        } catch (e) {
            let message: string = 'Login attempt failed, please try again later.';

            if (e && e.error_description) {
                message = e.error_description;
            }
            this.alertCtrl
                .create({
                    title: 'Login Failed',
                    message: message,
                    buttons: [
                        {
                            text: 'Dismiss',
                            handler: () => {
                                window.scrollTo(0, 0);
                                window.document.body.scrollTop = 0;
                            },
                        },
                    ],
                    enableBackdropDismiss: true,
                })
                .present();
            this.isEnabled = false;
            loadingCtrl.dismiss();
        }
    }
}

I also added <preference name="KeyboardDisplayRequiresUserAction" value="false" /> in the config.xml file still doesn’t work. Please assist. Thank you.