离子 - 如何正确导入视图控制器?- 未捕获(承诺):错误:视图控制器没有提供程序

Question

我有一个弹出框，我希望我的应用程序根据所选项目的不同而有所不同。为了实现这一目标，我遵循了那个离子文档。

 Error: Uncaught (in promise): Error: No provider for ViewController!

因此，如果我将视图控制器添加到app.module.ts，则会收到以下错误：

Uncaught Error: Can't resolve all parameters for ViewController: (?, ?, ?)

问：如何正确导入视图控制器？

弹出框组件：

import { Component } from '@angular/core';
import { ViewController } from 'ionic-angular';
@Component({
  selector: 'popover',
  templateUrl: 'popover.html'
})
export class PopoverComponent {
  popoverItemList = [{name: 'Event erstellen'}, {name: 'Event Übersicht'}];
  selectedTitle: string;
  constructor(private viewCtrl: ViewController) {
    this.selectedTitle = "";
  }
  setSelectedTitle(selectedItem) {
   this.selectedTitle = selectedItem;
    this.viewCtrl.dismiss(this.selectedTitle);
  }
}

我这样称呼弹出框：

presentPopover(ev) {
   let popover = this.popoverCtrl.create(PopoverComponent, {
   });
   popover.present({
     ev: ev
   });
   popover.onDidDismiss((popoverData) => {
      if(popoverData === 'Event erstellen') {
        this.navCtrl.push(CreateEventPage, {
        });
      } else if(popoverData === 'Event Übersicht') {
        this.navCtrl.push(EventlistPage, {
        });
      }
    })

Answer 1

从 '@angular/core' 导入 { ViewChild };从"ionic-angular"导入 { 视图控制器 };

不是在构造中声明，而是在@ViewChild（视图控制器）视图中声明：视图控制器;

Answer 2

import { ModalController } from   '@ionic/angular';
constructor(private viewCtrl : ModalController) { }
this.viewCtrl.dismiss();

Answer 3

import { Component } from '@angular/core';
import { ViewController } from 'ionic-angular';
@Component({
  selector: 'popover',
  templateUrl: 'popover.html',
  providers : [ViewController] //add this line
})
export class PopoverComponent {
  popoverItemList = [{name: 'Event erstellen'}, {name: 'Event Übersicht'}];
  selectedTitle: string;
  constructor(private viewCtrl: ViewController) {
    this.selectedTitle = "";
  }
  setSelectedTitle(selectedItem) {
   this.selectedTitle = selectedItem;
    this.viewCtrl.dismiss(this.selectedTitle);
  }
}