Ionic 3 无法在回调函数中拒绝承诺

Question

我在 Ionic 3 中编写了一个函数来获取用户的位置并使用用户的经度和纬度获取其地址。此功能还检查用户的位置设置是否启用，如果没有，它将调用this.diagnostic.switchToLocationSettings() 它基本上显示位置设置供用户打开。我还添加了this.diagnostic.registerLocationStateChangeHandler 方法来检查用户是否真的在我之前显示的位置设置中打开了位置。如果一切正常，我将继续运行其他流程，例如获取地理位置并转换为地址。

下面是我的完整代码：

  getMyLocation() {
    this.geoOptions = {
      enableHighAccuracy: false
    }
    const loadingMsg = this.loadingCtrl.create({
      content: "Getting your location..."
    })

    loadingMsg.present();



    this.diagnostic.isLocationEnabled().then(test => {
        this.diagnostic.registerLocationStateChangeHandler((state)=>{
        if((this.platform.is('ios')) && (state !== this.diagnostic.permissionStatus.GRANTED ||
           state !== this.diagnostic.permissionStatus.GRANTED_WHEN_IN_USE) ||
           (this.platform.is('android')) && (state === this.diagnostic.locationMode.LOCATION_OFF )){
            return Promise.reject("Please switch on your location");
          }
       })
      if (!test) {
        this.diagnostic.switchToLocationSettings()
      }

      // return this.geolocation.getCurrentPosition(this.geoOptions)
      return this.geolocation.getCurrentPosition(this.geoOptions)
      // console.log("Error! Please switch on your location");
      // return Promise.reject("Error! Please switch on your location");
    },(err:any)=>{
      loadingMsg.dismiss();
      console.log("error : " + err);

    }).then((pos: Geoposition) =>{

      return this.nativeGeocoder.reverseGeocode(pos.coords.latitude, pos.coords.longitude);

    },(err: PositionError)=>{
      loadingMsg.dismiss();
      console.log("error : " + err.message);
      return Promise.reject(err.message);

    }).then((result: NativeGeocoderReverseResult) =>{

      this.currentAddress = result.locality+", "+result.countryName;
      loadingMsg.dismiss();

    },(err:any)=>{

      console.log("error : " + err);
      loadingMsg.dismiss();
      return Promise.reject(err);

    })
  }

问题是如果在this.diagnostic.switchToLocationSettings() 被解雇后用户没有打开，我无法停止承诺链接。我试图停止链接的地方是在this.diagnostic.registerLocationStateChangeHandler 回调函数中。我是初学者承诺链式方法。

Answer 1

你可以这样做：

即您可以在需要abort promise chain的地方使用throw new Error('abort promise chain');return null;。

 this.diagnostic.isLocationEnabled().then(test => {
        this.diagnostic.registerLocationStateChangeHandler((state)=>{
        if((this.platform.is('ios')) && (state !== this.diagnostic.permissionStatus.GRANTED ||
           state !== this.diagnostic.permissionStatus.GRANTED_WHEN_IN_USE) ||
           (this.platform.is('android')) && (state === this.diagnostic.locationMode.LOCATION_OFF )){
            throw new Error('abort promise chain');//here
            return null;
          }
       })