Javascript Angular 4 typescript Cordova摄像头插件错误“；财产'；摄像机&x27；不存在于类型'；导航器&x27&引用；

我正在尝试使用Cordova构建APK。Web部件代码是用Angular 4 typescript编写的。当ng构建时，它给了我以下错误

$/AngularCordova/my app/src/app/app.component.ts中的错误（19,26）： 类型“Navigator”上不存在属性“camera”。错误 $/AngularCordova/my app/src/app/app.component.ts（23,13）：提供 参数与调用目标的任何签名都不匹配

我在openCamera函数中替换了上面的代码。发生错误是因为我试图从窗口对象访问navigator对象

    import { Component, OnInit } from '@angular/core';

declare let cordova: any;
declare let navigator: any;
let device;

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent  implements OnInit {
    title = 'angular app';
    ngOnInit(){
      this.deviceinfo();
    }
    deviceinfo(){

        document.addEventListener('deviceready', () => {
        alert("On device ready event");
            try{
                alert('Using Cordova plugins with Angular 4. Cordova version: ');
            }catch(e){
                alert("Exception occures"+ e)
            }
        }, false)
    }
  openCamera() {
      if( window.navigator != undefined){
        window.navigator.camera.getPicture(
          (imageUri) => {
            alert(imageUri);
          }, 
          (error) =>{
            alert("Unable to obtain picture: " + error, "app");

          }, {
              quality: 50,
              allowEdit: true,
              correctOrientation: true  //Corrects Android orientation quirks
          }
        );

    }
  }
}

if( navigator != undefined){
  navigator.camera.getPicture(
    (imageUri) => {
      alert(imageUri);
    },
    (error) =>{
      alert("Unable to obtain picture: "+error);

    }, {
      quality: 50,
      allowEdit: true,
      correctOrientation: true  
    }
  );

}