Question

我正在开发xamarin android app。我试图在oncreate方法中获取纬度，经度和城市名称以传递给服务。但是我只在onlocation change方法中获取这些值，并且无法在oncreate中获取这些值以传递给服务。

有人可以帮我解决这个问题吗？感谢。

 namespace Myapp
    {
        [Activity(Label = "Test")]
        class Test: AppCompatActivity, ILocationListener
        {

            LocationManager locMgr;

            string tag = "Test";

            private Android.Support.V7.Widget.Toolbar mToolBar;
            private RecyclerView mRecyclerView;
            private RecyclerView.LayoutManager mLayoutManager;
            private MyAdapter mAdapter;


            public static string latitude = null;
            public static string longitude = null;
            public static string cityname = null;



            protected async override void OnCreate(Bundle bundle)
            {
                base.OnCreate(bundle);
                SetContentView(Android.Resource.Layout.test);
                mToolBar = FindViewById<Android.Support.V7.Widget.Toolbar>(Android.Resource.Id.toolbar);
                SetSupportActionBar(mToolBar);
                SupportActionBar.Title = "Test";
                Window.AddFlags(WindowManagerFlags.DrawsSystemBarBackgrounds);
                mRecyclerView = FindViewById<RecyclerView>(Android.Resource.Id.testing);

               mLayoutManager = new LinearLayoutManager(this);
                mRecyclerView.SetLayoutManager(mLayoutManager);


                ProgressDialog progress = new ProgressDialog(this);
                progress.Indeterminate = true;
                progress.SetProgressStyle(ProgressDialogStyle.Spinner);
                progress.SetMessage("Contacting server. Please wait...");
                progress.SetCancelable(false);
                progress.Show();


                locMgr = GetSystemService(Context.LocationService) as LocationManager;


                if (locMgr.AllProviders.Contains(LocationManager.NetworkProvider)
                    && locMgr.IsProviderEnabled(LocationManager.NetworkProvider))
                {
                    locMgr.RequestLocationUpdates(LocationManager.NetworkProvider, 2000, 1, this);
                }
                else
                {
                    Toast.MakeText(this, "The Network Provider does not exist or is not enabled!", ToastLength.Long).Show();
                }

    **Here I need to pass the latitude, longitude and city name to my service.**       

                  progress.Dismiss();



                    mAdapter = new MyAdapter(Count, mRecyclerView, this);
                    //  mAdapter.ItemClick += OnItemClick;
                    mRecyclerView.SetAdapter(mAdapter);
                }



            }


            public async void GetAddress()
            {
                Geocoder geocoder = new Geocoder(this);
                IList<Address> addressList = await geocoder.GetFromLocationAsync(Convert.ToDouble(latitude), Convert.ToDouble(longitude), 10);

                Address address = addressList.FirstOrDefault();
                if (address != null)
                {
                    StringBuilder deviceAddress = new StringBuilder();
                    for (int i = 0; i < address.MaxAddressLineIndex; i++)
                    {
                        deviceAddress.Append(address.GetAddressLine(i))
                                     .AppendLine(",");
                    }

                    cityname = address.GetAddressLine(1);
                 //   Toast.MakeText(this, address.GetAddressLine(1), ToastLength.Long).Show();
                }
                else
                {
                   // _addressText.Text = "Unable to determine the address.";

                }
            }


            public void OnLocationChanged(Android.Locations.Location location)
            {
              //  Log.Debug(tag, "Location changed");
             //   latitude.Text = "Latitude: " + location.Latitude.ToString();
             //   longitude.Text = "Longitude: " + location.Longitude.ToString();
             //   provider.Text = "Provider: " + location.Provider.ToString();


                latitude = location.Latitude.ToString();
                longitude = location.Longitude.ToString();

                GetAddress();

             //   String[] s = cityname.Split(',');



            }
            public void OnProviderDisabled(string provider)
            {
                Log.Debug(tag, provider + " disabled by user");
            }
            public void OnProviderEnabled(string provider)
            {
                Log.Debug(tag, provider + " enabled by user");
            }
            public void OnStatusChanged(string provider, Availability status, Bundle extras)
            {
                Log.Debug(tag, provider + " availability has changed to " + status.ToString());
            }





        }
    }

Answer 1

与桌面编程不同，在Android上，您无法处理应用程序的生命周期步骤。只有在生命周期发生变化并在那里处理时，您才会收到通知。简而言之，获取最新位置的唯一方法是等待onLocationChanged被调用。

我的建议是在onLocationChanged方法中启动服务或启动服务，然后在调用onLocationChanged时，将位置传达给您的服务。或者您的服务可能是LocationListener并绕过那里的通信。

Answer 2

下面是我编写的一个简单示例的链接，该示例演示如何在OnCreate中创建位置请求，然后在OnLocationChanged中获取结果。您已经拥有类成员的经度和纬度变量。您可以在OnLocationChanged中设置这些变量，但需要从OnLocationChanged调用使用这些值执行某些操作的代码。

https://github.com/LCC-CIT/CS235AM-Demos/tree/master/GeolocationDemo/FusedLoationProvider

如何在android xamarin中获取从onlocationchanged到oncreate的值？

2 个答案: