问即使在使用MenuController启用菜单之后，也无法在Ionic 3中看到sidemenu图标

EN

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {

  constructor(public navCtrl: NavController, private menu: MenuController) {
    this.menu.enable(true);
  }

  accountSettings() {
    this.navCtrl.push(AccountSettingsPage);
  }

  logout() {
    this.navCtrl.push(LoginPage);
  }

}

<ion-header>
  <ion-navbar hideBackButton="true">
    <button ion-button menuToggle>
      <ion-icon name="menu"></ion-icon>
    </button>
    <ion-title>Home</ion-title>
    <ion-buttons end>
      <button (click)="accountSettings()" icon-only ion-button>
        <ion-icon name="settings"></ion-icon>
      </button>
      <button (click)="logout()" icon-only ion-button>
        <ion-icon name="log-out"></ion-icon>
      </button>
    </ion-buttons>
  </ion-navbar>
</ion-header>

<ion-content padding>
 //some more code here
</ion-content-padding>

@IonicPage()
@Component({
  selector: 'page-add-contract',
  templateUrl: 'add-contract.html',
})
export class AddContractPage {

   constructor(private formBuilder: FormBuilder, private navCtrl: NavController, private menu: MenuController) {
    this.menu.enable(false);
   }

   ionViewDidEnter() {
      this.menu.swipeEnable(false);
   }

   ionViewDidLeave() {
     this.menu.swipeEnable(true);
     this.menu.enable(true);
   }

   //takes the user to Home page
   addContract(val: any) {
      this.navCtrl.push(HomePage);
   }
}