GPS位置始终返回null

Question

我正在尝试访问活动中的gps位置，但是在调用null类的getLastKnownLocation时总是得到LocationManager。我还添加了以下权限。我的GPS已启用，并且设备上没有互联网。请指导我我在做什么错

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

，并签入代码。下面是我的代码。

public class MainActivity extends  AppCompatActivity implements LocationListener {
    private TextView latituteField;
    private TextView longitudeField;
    private LocationManager locationManager;
    private String provider;

    /** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        try {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
                    != PackageManager.PERMISSION_GRANTED) {

                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        2);

            }
        } catch (Exception e) {
            e.printStackTrace();
        }


        latituteField = (TextView) findViewById(R.id.TextView02);
        longitudeField = (TextView) findViewById(R.id.TextView04);

        // Get the location manager
        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
        Location location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if (location != null){
            latituteField.setText(location.getLatitude()+"");
            longitudeField.setText(location.getLongitude()+"");
        }else{
            latituteField.setText("not found");
            longitudeField.setText("not found");
        }

    }



    @Override
    public void onLocationChanged(Location location) {
        int lat = (int) (location.getLatitude());
        int lng = (int) (location.getLongitude());
        latituteField.setText(String.valueOf(lat));
        longitudeField.setText(String.valueOf(lng));
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String provider) {
        Toast.makeText(this, "Enabled new provider " + provider,
                Toast.LENGTH_SHORT).show();

    }

    @Override
    public void onProviderDisabled(String provider) {
        Toast.makeText(this, "Disabled provider " + provider,
                Toast.LENGTH_SHORT).show();
    }
}

Answer 1

在您的build.gradle中实现它，

implementation 'com.google.android.gms:play-services-location:17.0.0'

尝试此代码。对我来说很好。.

package com.example.geolocation;

import android.Manifest;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationCallback;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationResult;
import com.google.android.gms.location.LocationServices;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

public class MainActivity extends AppCompatActivity implements LocationListener {
    private TextView latituteField;
    private TextView longitudeField;
    private LocationManager locationManager;
    private String provider;
    private FusedLocationProviderClient fusedLocationClient;
    private String TAG=MainActivity.class.getSimpleName();
    LocationCallback mLocationCallback;

    /** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        try {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
                    != PackageManager.PERMISSION_GRANTED) {

                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        2);

            }
        } catch (Exception e) {
            e.printStackTrace();
        }


        latituteField = (TextView) findViewById(R.id.TextView02);
        longitudeField = (TextView) findViewById(R.id.TextView04);

        // Get the location manager
        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER))
            Log.d(TAG, "onCreate: not enabled gps");
        else {
            LocationRequest mLocationRequest = LocationRequest.create();
            mLocationRequest.setInterval(60000);
            mLocationRequest.setFastestInterval(5000);
            mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
            mLocationCallback = new LocationCallback() {
                @Override
                public void onLocationResult(LocationResult locationResult) {
                    if (locationResult == null) {
                        Log.d(TAG, "locationStatusCheck: onLocationResult null");
                        return;
                    }
                    for (Location location : locationResult.getLocations()) {
                        if (location != null) {
                            //TODO: UI updates.
                            Log.d(TAG, "locationStatusCheck: onLocationResult not null");
                            double lat = (location.getLatitude());
                            double lng = (location.getLongitude());
                            latituteField.setText(String.valueOf(lat));
                            longitudeField.setText(String.valueOf(lng));
                            Log.d(TAG, "latitudeField: " + latituteField);
                            Log.d(TAG, "longitudeField: " + longitudeField);
                        }
                    }
                }
            };
            LocationServices.getFusedLocationProviderClient(getApplicationContext()).requestLocationUpdates(mLocationRequest, mLocationCallback, null);
        }
    }
    @Override
    public void onLocationChanged(Location location) {
        int lat = (int) (location.getLatitude());
        int lng = (int) (location.getLongitude());
        latituteField.setText(String.valueOf(lat));
        longitudeField.setText(String.valueOf(lng));
    }

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

    }

    @Override
    public void onProviderEnabled(String provider) {
        Toast.makeText(this, "Enabled new provider " + provider,
                Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onProviderDisabled(String provider) {
        Toast.makeText(this, "Disabled provider " + provider,
                Toast.LENGTH_SHORT).show();
    }
}