这就是我试图在我的Android应用程序中获取位置的方式。但每次我启动我的应用程序时它给我NullPointerException但我检查该位置是否为空。这里发生了什么？请帮帮我。
public Location getLocation () {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
if (isNetworkEnabled) {
//updates will be send according to these arguments
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return location;
}
这个方法在我正在调用的服务中运行。我正在使用AsyncTask将我的位置发送到服务器这样：
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();
Log.i(LOG, "Service started");
Log.i("asd", "This is sparta");
new SendToServer().execute(Double.toString(getLocation().getLongitude()),Double.toString(getLocation().getLatitude());
return START_STICKY;
}
这是我的logcat：
3-04 12:55:03.748 3235-3235/sourcemate.com.locationsender E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: sourcemate.com.locationsender, PID: 3235
java.lang.RuntimeException: Unable to start service sourcemate.com.locationsender.LocationService@2f790e5a with Intent { cmp=sourcemate.com.locationsender/.LocationService }: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLongitude()' on a null object reference
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2914)
at android.app.ActivityThread.access$2100(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1401)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLongitude()' on a null object reference
at sourcemate.com.locationsender.LocationService.onStartCommand(LocationService.java:75)
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:2897)
at android.app.ActivityThread.access$2100(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1401)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
答案 0 :(得分：0)
请将此课程用于地点。
import android.Manifest;
import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
// flag for GPS status
public boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
// flag for GPS status
boolean canGetLocation = false;
//flag for WIFi
boolean isWifiEnabled = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
// private static final long MIN_TIME_BW_UPDATES = 1000 ; // 1 sec
// Declaring a Location Manager
protected LocationManager locationManager;
public GPSTracker(Context context) {
this.mContext = context;
getLocation();
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
isWifiEnabled = locationManager.isProviderEnabled(LocationManager.PASSIVE_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled && !isWifiEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
if (isWifiEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.PASSIVE_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
if (String.valueOf(latitude).equalsIgnoreCase("0.0") || String.valueOf(longitude).equalsIgnoreCase("0.0")) {
// showSettingsAlert();
canGetLocation = false;
}
}
} catch (Exception e) {
}
return location;
}
/**
* Stop using GPS listener
* Calling this function will stop using GPS in your app
* */
public void stopUsingGPS() {
if (locationManager != null) {
if (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// public void requestPermissions(@NonNull String[] permissions, int requestCode)
// 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 Activity#requestPermissions for more details.
return;
}
locationManager.removeUpdates(GPSTracker.this);
}
}
/**
* Function to get latitude
* */
public double getLatitude(){
if(location != null){
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
* */
public double getLongitude(){
if(location != null){
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
/**
* Function to check GPS/wifi enabled
* @return boolean
* */
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
* On pressing Settings button will lauch Settings Options
* */
public void showSettingsAlert(){
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext,AlertDialog.THEME_HOLO_LIGHT);
// Setting Dialog Title
alertDialog.setTitle("GPS settings");
// Setting Dialog Message
alertDialog.setMessage("GPS is not enabled. Please turn ON GPS.");
// On pressing Settings button
alertDialog.setNeutralButton("Settings", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// Showing Alert Message
alertDialog.show();
}
@Override
public void onLocationChanged(Location location) {
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public IBinder onBind(Intent arg0) {
return null;
}
}
并将此类用作 -
GPSTracker gps = new GPSTracker(CLASSNAME.this);
double latitude = gps.getLatitude();
double longitude = gps.getLongitude();
修改
请在清单文件中添加。
<!-- Required to show current location -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
答案 1 :(得分：0)
**I see that you want the Current Lat and Long of the User, the above method using GPS is not efficient.
Try this to Get the Lat and Long**
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
private GoogleApiClient mGoogleApiClient;
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
mLocationRequest = LocationRequest.create()
.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
.setInterval(10 * 1000) // 10 seconds, in milliseconds
.setFastestInterval(1 * 1000); // 1 second, in milliseconds
public class YourActivity extends AppCompact implements
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener {
@Override
public void onConnected(Bundle bundle) {
Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
if (location == null) {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
else {
handleNewLocation(location);
}
}
@Override
public void onConnectionSuspended(int i) {
Log.i(TAG, "Location services suspended. Please reconnect.");
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
mGoogleApiClient.connect();
}
@Override
protected void onPause() {
super.onPause();
if (mGoogleApiClient.isConnected()) {
mGoogleApiClient.disconnect();
}
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
if (connectionResult.hasResolution()) {
try {
// Start an Activity that tries to resolve the error
connectionResult.startResolutionForResult(this, CONNECTION_FAILURE_RESOLUTION_REQUEST);
} catch (IntentSender.SendIntentException e) {
e.printStackTrace();
}
} else {
Log.i(TAG, "Location services connection failed with code " + connectionResult.getErrorCode());
}
@Override
public void onLocationChanged(Location location) {
handleNewLocation(location);
}
答案 2 :(得分：0)
为此创建服务。 它的功能是获取lat和lng。
public class Location_Service extends Service implements
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener {
private Handler handler = new Handler();
private GoogleApiClient mGoogleApiClient;
private LocationRequest mLocationRequest;
public static final String BROADCAST_ACTION = "Hello World";
private static final int TWO_MINUTES = 2;
public MyLocationListener listener;
public Location previousBestLocation = null;
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
intent = new Intent(BROADCAST_ACTION);
mGoogleApiClient.connect();
return START_STICKY;
}
@Override
public void onCreate() {
super.onCreate();
}
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onConnected(Bundle bundle) {
if (mGoogleApiClient.isConnected()) {
mLocationRequest = LocationRequest.create();
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
mLocationRequest.setInterval(10000); // Update location every second
listener = new MyLocationListener();
LocationServices.FusedLocationApi.requestLocationUpdates(
mGoogleApiClient, mLocationRequest, listener);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
public class MyLocationListener implements LocationListener {
public void onLocationChanged(final Location loc) {
// Log.i("**************************************", "Location changed");
if (isBetterLocation(loc, previousBestLocation)) {
// Log.e("Lat/Long : ", "" + loc.getLatitude() + "/" + loc.getLongitude());
// Log.d("Provider : ", "" + loc.getProvider());
Utils._LATITUDE = Double.parseDouble(String.valueOf(loc.getLatitude()));
Utils._LONGITUDE = Double.parseDouble(String.valueOf(loc.getLongitude()));
}
}
}
protected boolean isBetterLocation(Location location,
Location currentBestLocation) {
if (currentBestLocation == null) {
// A new location is always better than no location
return true;
}
// Check whether the new location fix is newer or older
long timeDelta = location.getTime() - currentBestLocation.getTime();
boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
boolean isNewer = timeDelta > 0;
// If it's been more than two minutes since the current location, use
// the new location
// because the user has likely moved
if (isSignificantlyNewer) {
return true;
// If the new location is more than two minutes older, it must be
// worse
} else if (isSignificantlyOlder) {
return false;
}
// Check whether the new location fix is more or less accurate
int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation
.getAccuracy());
boolean isLessAccurate = accuracyDelta > 0;
boolean isMoreAccurate = accuracyDelta < 0;
boolean isSignificantlyLessAccurate = accuracyDelta > 200;
// Check if the old and new location are from the same provider
boolean isFromSameProvider = isSameProvider(location.getProvider(),
currentBestLocation.getProvider());
// Determine location quality using a combination of timeliness and
// accuracy
if (isMoreAccurate) {
return true;
} else if (isNewer && !isLessAccurate) {
return true;
} else if (isNewer && !isSignificantlyLessAccurate
&& isFromSameProvider) {
return true;
}
return false;
}
/**
* Checks whether two providers are the same
*/
private boolean isSameProvider(String provider1, String provider2) {
if (provider1 == null) {
return provider2 == null;
}
return provider1.equals(provider2);
}
}
在你的清单文件中添加以下行
<!-- Required to show current location -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
答案 3 :(得分：0)
花了很多时间解决这个问题之后，我终于意识到GPS不能在任何地方工作，就我而言，我的停车场和办公楼，除非有wifi或启用并使用网络定位服务，否则不可以。