ionic2APP 如何處理返回鍵問題

1、APP中難免會有自定義各種modal、alert，modal或alert處於激活狀態時android用戶按物理返回鍵，頁面被返回，而這些彈窗切沒有被返回，一種解決辦法是可以在每個組件內用生命周期鈎子ionViewWillLeave監聽有modal或是alert的頁面，如果處於激活狀態則先關閉它，當然這種狀態簡單卻不高效；

2、封裝一個服務，代碼如下

import {Injectable} from '@angular/core';
import {Subject}    from 'rxjs/Subject';
import {TranslateService} from 'ng2-translate';

@Injectable()
export class ToastService {
  comfirmSubject = new Subject();

  // comfirmObservable$ = this.comfirmSubject.asObservable();
  _isActive = false;
  gobackWhenClose = false;
  model = null;
  is_access_modal:boolean = false;

  set isActive(active: boolean) {
    if(active) {
      this._isActive = true;
    } else {
      this._isActive = false;
      if(this.model) {
        this.model.dismiss();
        this.model = null;
      }
    }


  }

  get isActive() {
    return this._isActive || this.model;
  }

  constructor(private translate: TranslateService) {}

  // 普通彈框
  confirm(params: any) {
    this.comfirmSubject.next(params);
    this.isActive = true;
  }

  // 業務成功后彈框，title帶成功的icon
  successConfirm(params: any) {
    params = Object.assign(params, {
      title: `<i class="icon-icons icon-icons-success"></i><span>${params['title'] || this.translate.get('TIPS.WENXINTISHI')['value']}</span>`
    });
    this.comfirmSubject.next(params);
    this.isActive = true;
  }

  // 業務失敗后彈框
  errorConfirm(params: any) {
    params = Object.assign(params, {
      title: `<i class="icon-icons icon-icons-error"></i><span>${params['title'] || this.translate.get('TIPS.WENXINTISHI')['value']}</span>`
    });

    // 錯誤提示處理
    let feedbacks = this.translate.get('FEEDBACK')['value'];

    let content = params['body'];
    if (content) {
      if (content.indexOf('MSG.CLINETFUNDNOTENOUGH') > -1) {  //購買基金余額不足時，后台返回數據做了拆分
        params['body'] = feedbacks['MSG.CLIENTFUNDNOTENOUGH'] + '<span class="red">'+ content.split('|')[1] + '</span>'
      } else {
        params['body'] = feedbacks[content] || content;
      }
    }

    this.comfirmSubject.next(params);
    this.isActive = true;
  }
}

然后在APP.component.ts中去監聽Android物理返回鍵，

}
if ( this.toastService.isActive && !this.toastService.is_access_modal) { // 當前有自定義toast，關閉toast
  this.toastService.isActive = false;  //包括toast和model
  if(this.toastService.gobackWhenClose) {
    this.toastService.gobackWhenClose = false;
    this.toastService._isActive = false;
    this.events.publish('backto');
  }
  return;
}

其中有多余的代碼（為了符合自己業務需求，主要是isActive這個變量及

this.toastService.isActive = false;

，請忽略多余沒用的代碼；