我正在开发基于小型位置的Android应用程序，其中我需要用户当前位置。一旦发生某些位置变化，我也会更新用户的当前位置。我的代码如下：
private final LocationListener locationListener = new LocationListener() {
public void onLocationChanged(Location location) {
updateWithNewLocation(location);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status,
Bundle extras) {}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LocationManager locationManager;
String svcName = Context.LOCATION_SERVICE;
locationManager = (LocationManager)getSystemService(svcName);
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setPowerRequirement(Criteria.POWER_LOW);
criteria.setAltitudeRequired(false);
criteria.setBearingRequired(false);
criteria.setSpeedRequired(false);
criteria.setCostAllowed(true);
String provider = locationManager.getBestProvider(criteria, true);
//Location l = locationManager.getLastKnownLocation(locationManager.NETWORK_PROVIDER);
Location l = locationManager.getLastKnownLocation(provider);
updateWithNewLocation(l);
locationManager.requestLocationUpdates(provider, 2000, 10, locationListener);
}
private void updateWithNewLocation(Location location)
{
TextView myLocationText;
myLocationText = (TextView)findViewById(R.id.myLocationText);
String latLongString = "No location found";
if (location != null) {
double lat = location.getLatitude();
double lng = location.getLongitude();
latLongString = "Lat:" + lat + "\nLong:" + lng;
}
myLocationText.setText("Your Current Position is:\n" +
latLongString);
}
我的问题是，当我使用提供商作为网络时，它工作正常。但是当它选择gps作为提供者时，它会给出null值。我第一次知道它给了我空值。我也使用onLocationChanged方法，但它仍然没有给我正确的输出。 当我打开我的应用程序时，它显示输出空值，它也启动gps以获取我的位置。我等了一段时间才得到更新的位置，但它没有给我有效的输出。 我的代码有什么问题吗？ 我正在使用android设备。
需要帮助......谢谢......
答案 0 :(得分：0)
更改此行
Location l = locationManager.getLastKnownLocation(provider);
locationManager.requestLocationUpdates(provider, 2000, 10, locationListener);
到
Location l = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
locationManager.requestLocationUpdates( LocationManager.GPS_PROVIDER, 2000, 10, locationListener);
然后我认为它会起作用。
或者您可以按照this教程使用gps获取位置
答案 1 :(得分：0)
您是否在清单中输入了这些权限？
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_GPS"/>
答案 2 :(得分：0)
当您使用提供商作为网络时，您会立即获得该位置，因为它获取网络提供商的最近塔的位置值。但是当您使用GPS时，需要一些时间来获取当前位置值。在您的情况下（看到代码之后），很明显您使用网络提供程序获取最后一个已知位置，因此它获取位置，并且在使用gps提供程序时需要一些时间，更重要的是如果您在近距离区域，则需要更多时间通过gps提供程序获取位置值。
答案 3 :(得分：0)
此处，系统正在尝试根据您设置的标准选择最佳提供商
e.g. criteria.setPowerRequirement(Criteria.POWER_LOW);
但GPS提供商不符合您指定的标准。 这就是为什么它可能无法正常工作。要么更改标准，要么只想从GPS提供商获取位置更新，然后使用以下代码，
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,2000, 10, locationListener);
答案 4 :(得分：0)
请在使用用户当前位置时使用此课程
private GPSTracker gps;
gps = new GPSTracker(this);
if (gps.canGetLocation()) {
/*----get Lat and Long---------*/
double lat = gps.getLatitude();
double lon = gps.getLongitude();
String mLatitute = Double.toString(lat);
String mLongitute = Double.toString(lon);
}
GPS追踪服务：
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
// flag for GPS status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
// flag for GPS status
boolean canGetLocation = false;
Location location = null; // 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
// 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);
if (!isGPSEnabled && !isNetworkEnabled) {
// 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.e("Network", "Network Enabled");
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.e("GPS", "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;
}
/**
* Stop using GPS listener Calling this function will stop using GPS in your
* app
* */
public void stopUsingGPS() {
if (locationManager != null) {
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);
// Setting Dialog Title
alertDialog.setTitle("GPS is settings");
// Setting Dialog Message
alertDialog
.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// On pressing Settings button
alertDialog.setPositiveButton("Settings",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Intent intent = new Intent(
Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
public void onLocationChanged(Location location) {
}
public void onProviderDisabled(String provider) {
}
public void onProviderEnabled(String provider) {
}
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public IBinder onBind(Intent arg0) {
return null;
}
}