位置经度和纬度为空

Question

我的经度和纬度变量为空。

GpsTracker.java

package com.mymate.myownidea.fawad.my_mate;

import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import static android.content.Context.LOCATION_SERVICE;

/**
 * Created by shiva on 8/4/17.
 */

public class GpsTracker implements LocationListener {

    Context context;

    public GpsTracker(Context context) {
        super();
        this.context = context;
    }

    public Location getLocation(){
        if (ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED) {
            Log.e("fist","error");
            return null;
        }
        try {
            LocationManager lm = (LocationManager) context.getSystemService(LOCATION_SERVICE);
            boolean isGPSEnabled = lm.isProviderEnabled(LocationManager.GPS_PROVIDER);
            if (isGPSEnabled){
                lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 6000,10,this);
                Location loc = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                return loc;
            }else{
                Log.e("sec","errpr");
            }
        }catch (Exception e){
            e.printStackTrace();
        }
        return null;
    }

    @Override
    public void onLocationChanged(Location location) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onProviderDisabled(String provider) {
    }
}

和MainMenu.java

package com.mymate.myownidea.fawad.my_mate;

import android.location.Location;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.text.TextUtils;
import android.view.View;
import android.widget.Toast;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;



public class MainMenuActivity extends FragmentActivity {


    String user_type;

    Bundle bundle;

    Fragment newFragment;

    private FirebaseAuth mAuth;
    String uid;
    DatabaseReference rootRef;
    DatabaseReference uidRef;
    FirebaseUser currentFirebaseUser;

    public static String longitude;
    public static String latitude;
    String id;

    DatabaseReference databaseUser;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_menu);


        ActivityCompat.requestPermissions(MainMenuActivity.this, new String[] {
                android.Manifest.permission.ACCESS_FINE_LOCATION}, 123);

        GpsTracker gt = new GpsTracker(getApplicationContext());
        Location l = gt.getLocation();
        if( l == null){
            Toast.makeText(getApplicationContext(),"GPS unable to get Value",Toast.LENGTH_SHORT).show();
        }else {
            double lat = l.getLatitude();
            double lon = l.getLongitude();
            Toast.makeText(getApplicationContext(),"GPS Lat = "+lat+"\n lon = "+lon,Toast.LENGTH_SHORT).show();
        }


        Toast.makeText(getApplicationContext(), longitude + " " + latitude, Toast.LENGTH_SHORT).show();

      }
}

我的经度和纬度为零。 导入android函数时发生错误或发生某种逻辑错误。 我已经尝试了许多功能，但始终为空。 或者我使用的是旧方法。

Answer 1

有时可能需要一段时间才能在手机上找到位置。 因此，调用getLastKnownLocation()可能需要一段时间才能返回非空结果。

相反，您应该在onLocationChanged方法中获取位置数据，当位置可用时将调用该数据。

Answer 2

创建一个界面

 interface IOnLocationChanged {
        void onLocationchanged(Location location);
    }

在GpsTracker

private  IOnLocationChanged iOnLocationChanged;

    public GpsTracker(Context context,IOnLocationChanged iOnLocationChanged) {
        super();
        this.context = context;
        this.iOnLocationChanged = iOnLocationChanged;
    }

在onLocationChanged

@Override
    public void onLocationChanged(Location location) {
       if(iOnLocationChanged!=null){
       iOnLocationChanged.onLocationchanged(location);
       }
    }

在MainMenuActivity

public class MainMenuActivity extends FragmentActivity implements IOnLocationChanged{

 @Override
    public void onLocationchanged(Location location) {
        //get Your location here
    }

}