我的位置应用程序未访问 getLastKnownLocation

Question

我正在尝试检索设备的位置，但由于某种原因没有接收到该位置。有人可以检查我的代码并让我知道代码中的错误是什么。谢谢。

MainActivity

 public class MainActivity extends AppCompatActivity implements LocationListener {
    LocationManager locManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        //get a reference to the location services to initialize the location manager object
        locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);


        // Creating an empty criteria object
        Criteria criteria = new Criteria();

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }

        // Get name of the provider in this case which would be gps
       // String provider = locManager.getBestProvider(criteria, false);

       // if (provider != null && !provider.equals("")) {
            // Get the location
          //  Location location = locManager.getLastKnownLocation(provider);


Location location = getLastKnownLocation();

        private Location getLastKnownLocation() {
            LocationManager mLocationManager = (LocationManager) getApplicationContext().getSystemService(LOCATION_SERVICE);
            List<String> providers = mLocationManager.getProviders(true);
            Location bestLocation = null;
            for (String provider : providers) {
                Location l = mLocationManager.getLastKnownLocation(provider);
                if (l == null) {
                    continue;
                }
                if (bestLocation == null || l.getAccuracy() < bestLocation.getAccuracy()) {
                    // Found best last known location: %s", l);
                    bestLocation = l;
                }
            }
            return bestLocation;
        }
            //set frequency of location update parameters
            locManager.requestLocationUpdates(provider, 120000, 10, this);

            if (location != null)
                onLocationChanged(location);
            else {
                TextView tvLongitude = (TextView) findViewById(R.id.curr_longitude);
                tvLongitude.setText("Location can't be retrieved");
                Toast.makeText(getBaseContext(), "Location can't be retrieved", Toast.LENGTH_SHORT).show();
            }

     /*   } else {
            //create a toast indicating error.
            Toast.makeText(getBaseContext(), "OOPS something went wrong", Toast.LENGTH_SHORT).show();

        }*/
}


    public void onLocationChanged(Location location) {
        // text view for company caption
        TextView jackFruit = (TextView) findViewById(R.id.jack_fruit);
        // Get TextView curr_longitude
        TextView tvLongitude = (TextView) findViewById(R.id.curr_longitude);

        // Getting TextView curr_latitude
        TextView tvLatitude = (TextView) findViewById(R.id.curr_latitude);

        // setting company caption
        jackFruit.setText("Jackfruit Systems: My current location");

        // Setting Current Longitude in the TextView
        tvLongitude.setText("Longitude:" + location.getLongitude());

        // Setting Current Latitude in the TextView
        tvLatitude.setText("Latitude:" + location.getLatitude());
    }

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

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
}

---

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.jackfruit.driverlocationinfo">

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

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

我为 sdk 版本 23 尝试了另一种方法。

MainActivity

 @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
// calling location service via location manager
        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        //calling location listener to get location coordinates on change of location
        locationListener = new LocationListener() {
            @Override
            public void onLocationChanged(Location location) {
                altitude = location.getAltitude();//calling altitude
                longitude = location.getLongitude();//calling longitude
                latitude = location.getLatitude();//calling latitude

                longitudeValue = Double.toString(longitude);//converting double longitude to string
                latitudeValue = Double.toString(latitude);//converting double latitude to string
                altitudeValue = Double.toString(altitude);//converting double altitude to string
            }

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

            }

            @Override
            public void onProviderEnabled(String provider) {

            }

            @Override
            public void onProviderDisabled(String provider) {
                //calling settings options in device when location is disabled
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                startActivity(intent);
            }
        };
        // adding permissions for location service for api level 23
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

            requestPermissions(new String[]{
                    Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION,
                    Manifest.permission.INTERNET
            }, 10);
            return;
        } else {
            //after above check start the method:
            locationConfiguration();
        }
}

    //another permission check if the first permissions miss any permission lib. packages
    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 10:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
                    locationConfiguration();
                return;
        }
    }


    //method to call location provider
    private void locationConfiguration() {
        provider = locationManager.getProvider(LocationManager.GPS_PROVIDER);
        location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000, 0, locationListener);
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 5000, 0, locationListener);
        provider.supportsAltitude();

    }

Answer 2

如果您为Android 6.0+编译应用程序，您需要在运行时请求权限。

有代码，Android Studio 建议Location location = locManager.getLastKnownLocation(provider); 行

if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }

这是官方文档的the link。

编辑 我试图在我的手机上运行这段代码。这没有用:) that question 的代码帮助了我：

public class MainActivity extends AppCompatActivity implements LocationListener {
 LocationManager locManager;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
  setSupportActionBar(toolbar);
  //get a reference to the location services to initialize the location manager object
  locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);


  // Creating an empty criteria object
  Criteria criteria = new Criteria();

  if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
   return;
  }

  // Get name of the provider in this case which would be gps
  // String provider = locManager.getBestProvider(criteria, false);

  // if (provider != null && !provider.equals("")) {
  // Get the location
  //  Location location = locManager.getLastKnownLocation(provider);


  Location location = getLastKnownLocation();


  //set frequency of location update parameters
  locManager.requestLocationUpdates(provider, 120000, 10, this);

  if (location != null)
   onLocationChanged(location);
  else {
   TextView tvLongitude = (TextView) findViewById(R.id.curr_longitude);
   tvLongitude.setText("Location can't be retrieved");
   Toast.makeText(getBaseContext(), "Location can't be retrieved", Toast.LENGTH_SHORT).show();
  }

  /*   } else {
                //create a toast indicating error.
                Toast.makeText(getBaseContext(), "OOPS something went wrong", Toast.LENGTH_SHORT).show();

            }*/
 }

 private Location getLastKnownLocation() {
  if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
   return;
  }
  LocationManager mLocationManager = (LocationManager) getApplicationContext().getSystemService(LOCATION_SERVICE);
  List < String > providers = mLocationManager.getProviders(true);
  Location bestLocation = null;
  for (String provider: providers) {
   Location l = mLocationManager.getLastKnownLocation(provider);
   if (l == null) {
    continue;
   }
   if (bestLocation == null || l.getAccuracy() < bestLocation.getAccuracy()) {
    // Found best last known location: %s", l);
    bestLocation = l;
   }
  }
  return bestLocation;
 }

 public void onLocationChanged(Location location) {
  // text view for company caption
  TextView jackFruit = (TextView) findViewById(R.id.jack_fruit);
  // Get TextView curr_longitude
  TextView tvLongitude = (TextView) findViewById(R.id.curr_longitude);

  // Getting TextView curr_latitude
  TextView tvLatitude = (TextView) findViewById(R.id.curr_latitude);

  // setting company caption
  jackFruit.setText("Jackfruit Systems: My current location");

  // Setting Current Longitude in the TextView
  tvLongitude.setText("Longitude:" + location.getLongitude());

  // Setting Current Latitude in the TextView
  tvLatitude.setText("Latitude:" + location.getLatitude());
 }

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

 }

 @Override
 public void onProviderEnabled(String provider) {

 }

 @Override
 public void onProviderDisabled(String provider) {

 }
}

对我来说，首选提供商是“gps”，但它返回null Location。

附：抱歉格式化。您可以在 Android Studio 中按 Ctrl+Alt+L 来正确格式化。