ERROR Error: Uncaught (in promise): Error: Modal content has more than one root view.
JS: Error: Modal content has more than one root view.

onLogin()
{
    if(this.loading)
        return;

    this.loading=true;
    let options: ModalDialogOptions = {
        viewContainerRef: this.vcRef,
        context:null,
        fullscreen: false
    };
    console.log("Vamos a entrar en login");
    this._modalService.showModal(ViewLogin, options)
        .then((userResult: User) => {
            if(userResult!=null)
                {
                    console.log("ENTRA el user = Object." + userResult.nombre);
                    this.usuario=userResult;
                    this.res["login"]=userResult;
                    app.setResources(this.res);
                }
                console.log("ENTRA en el USER = NULLLLL");
                this.loading=false;
        }).catch((error)=>{this.loading=false; alert(error);});
}

import { Component, OnInit } from "@angular/core";
import { User } from "../../Model/User/user";
import {UserService} from "../../Model/User/user.service"
import { Page } from "tns-core-modules/ui/page";
import aplicacion = require("tns-core-modules/application");
import aplicacionSet=require("tns-core-modules/application-settings");
import { ModalDialogParams } from "nativescript-angular/modal-dialog";
import { SelectedIndexChangedEventData } from "nativescript-drop-down";


@Component({
    selector: "login",
    providers: [UserService],
    templateUrl: "./modal/login/login.html",
    styleUrls: ["./modal/login/login-common.css"]
})

export class ViewLogin implements OnInit {
user: User;
estadoLog="";
clave="";

loading=false;
public selectedIndex=0;
public dependientes: Array<string>=[];


constructor(
    private params:ModalDialogParams,
    private userService:UserService,
    private page:Page)
{
    console.log("entrando en login");
    this.user=new User(null);
    this.user.usuario="";
    this.user.clave="";
    this.userService.listar().subscribe(
    (res:Array<User>)=>{
         res.forEach(element => {
             this.dependientes.push(element.usuario);
         });
         this.selectedIndex=0;
         console.log("ADENTRO DE LA FUNCION SUBSCRIBE ----- " + res.length);
        },
         (error)=>{
         console.log("Error al hacer LOGIN: " + error);
     });

     this.page.on("unloaded", () => {
         this.params.closeCallback(null);
         });
         console.log("DESPUES DEL page.on");
}

public onchange(args: SelectedIndexChangedEventData) {
    console.log('El usuario selecionado es ' + this.dependientes[args.newIndex] + " new-> " + args.newIndex + " select-> " + this.selectedIndex);
    this.user.usuario=this.dependientes[args.newIndex];
}

teclado(numero:string)
{
    if(numero=='back')
        this.user.clave=this.user.clave.substring(0,this.user.clave.length-1);
    else
        this.user.clave+=numero;
    this.clave= Array(this.user.clave.length+1).join("*") ;
}

ngOnInit()
{

    this.page.actionBarHidden=true;
    if(aplicacionSet.hasKey("usuario"))
        this.user.usuario=aplicacionSet.getString("usuario");

}

summit(){
    if(this.loading)
        return;
    this.loading=true;
    this.estadoLog="";
    var res=aplicacion.getResources();
    this.userService.login(this.dependientes[this.selectedIndex],this.user.clave).subscribe(
        (resultado:User)=>
                {
                    if(resultado==null)
                        {
                            console.log("Login incorrecto: " + resultado);
                            this.estadoLog="Login incorrecto"
                            res["login"]=null;
                            aplicacion.setResources(res);
                            this.loading=false;
                            return false;
                        }
                    else
                        {
                            this.estadoLog="Login correcto";
                            res["login"]=resultado;

                            aplicacion.setResources(res);
                            aplicacionSet.setString("usuario",this.user.usuario);
                            console.log("lo hemos logrado: " + resultado.nombre);
                            console.log("login correcto");
                            this.params.closeCallback(resultado);
                            this.loading=false;
                            return true;
                        }
                },
        (error)=>
                {
                    console.log("No ha hecho login: " + error);
                    this.estadoLog = "Login incorrecto";
                    res["login"]=null;
                    aplicacion.setResources(res);
                    this.loading=false;
                    return false;
                }
    );

}

volver()
{
    this.params.closeCallback(null);
}
}

JS: ERROR Error: Uncaught (in promise): Error: Modal content has more than

one root view.
JS: Error: Modal content has more than one root view.
JS: at `file:///data/data/org.adealoxica.picking/files/app/tns_modules/nativescript-angular/directives/dialogs.js:99:23 [angular]`
JS: at Object.onInvoke `(file:///data/data/org.adealoxica.picking/files/app/tns_modules/@angular/core/bundles/core.umd.js:17343:37) [angular]`
JS: at `file:///data/data/org.adealoxica.picking/files/app/tns_modules/nativescript-angular/zone-js/dist/zone-nativescript.js:883:34 [angular]`
JS: at Object.onInvokeTask `(file:///data/data/org.adealoxica.picking/files/app/tns_modules/@angular/core/bundles/core.umd.js:17334:37) [angular]`
JS: at drainMicroTaskQueue `(file:///data/data/org.adealoxica.picking/files/app/tns_modules/nativescript-angular/zone-js/dist/zone-nativescript.js:595:35) [angular]`
JS: at ZoneTask.invokeTask `(file:///data/data/org.adealoxica.picking/files/app/tns_modules/nativescript-angular/zone-js/dist/zone-nativescript.js:500:21) [angular]`
JS:    ...