我正在调查三星Galaxy2（Android 2.3.5）上的GPS位置。 SG2支持A-GPS，因此我开启了GPS，Wifi网络和传感器辅助功能。它看起来运作良好，但有时GPS提供了与我目前的地方相距50多公里的完全不同的位置。此外，即使我只是将手机放在一个地方并且从未接触过，这个位置也经常变化。
我还是Android新手，所以我不确定导致这个问题的原因。以下是处理GPS位置的源代码。：
public class LocationMonitor extends Service implements LocationListener,Runnable {
.... other local variables here
Object locationUpdateNotifier= null;
public static GeoPoint ourLocation;
public void synchronize()
{
if(ourLocation == null)
{
ourLocation = getLastKnownLocation();
if(ourLocation == null) return;
}
//Load last time we synced
long lastSyncTime = some_value;
if(lastSyncTime < System.currentTimeMillis() - UPDATE_FREQ) //UPDATE_FREQ - default 30 minutes
{
handler.post(new Runnable() {
public void run() {
GpsPingTask pingTask = new GpsPingTask(context,String.valueOf(ourLocation.getLatitudeE6()/1E6),String.valueOf(ourLocation.getLongitudeE6()/1E6));
pingTask.execute((Void)null); //Send location to server
}
});
lastSyncTime = System.currentTimeMillis();
//Save new lastSync time
}
}
public void kill()
{
if(locationManager !=null)
locationManager.removeUpdates(this);
}
public void onLocationChanged(Location location) {
try
{
//Read latitude and longitude from location
//Create Geo point so we can get a english street name address
ourLocation = new GeoPoint((int)(location.getLatitude()*1E6),(int)(location.getLongitude()*1E6));
if(locationUpdateNotifier != null)
{
synchronized (locationUpdateNotifier) {
locationUpdateNotifier.notify();
}
}
if(!doneFirstUpdate)
{
doneFirstUpdate =true;
Log.i("LocationMointor", "LocationMonitor.onLocationChanged() done first update at 0 frequency, resetting to normal speed");
//Set it to update at the requested frequency
resetLocationUpdatesFreq();
}
startSynchronizeThread();
}
catch (Throwable e) {
Log.i("LocationMointor", "LocationMonitor.onLocationChanged(): " + e);
}
}
public void onProviderDisabled(
String provider) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String provider) {}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {}
public void setTemporaryLocationUpdateFreq(int pingFreqSecs) {
setTemporaryLocationUpdateFreq(pingFreqSecs, 10);
}
public void setTemporaryLocationUpdateFreq(int pingFreqSecs, int minimumDistanceMeters) {
if(!doneFirstUpdate)
doneFirstUpdate =true;
tempLocationUpdateFreq = pingFreqSecs;
tempLocationUpdateMeters = minimumDistanceMeters;
handler.post(new Runnable()
{
public void run() {
//Turn of location updates
if(locationManager !=null)
locationManager.removeUpdates(locationMonitor);
//Restart location updates with new frequency
locationManager.requestLocationUpdates(getGpsMode(), UPDATE_FREQ, tempLocationUpdateMeters,locationMonitor);
//locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, tempLocationUpdateFreq*1000, tempLocationUpdateMeters,locationMonitor);
}
});
}
private void startSynchronizeThread() {
if(!running)
new Thread(this).start();
}
public void resetLocationUpdatesFreq() {
locationUpdateNotifier = null;
handler.post(new Runnable()
{
public void run() {
//Turn of location updates
if(locationManager !=null) {
locationManager.removeUpdates(locationMonitor);
//Restart location updates with default location update frequency
//locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, MINIMUM_TIME_BETWEEN_UPDATE, MINIMUM_DISTANCECHANGE_FOR_UPDATE,locationMonitor);
}
}
});
}
public void setLocationUpdateFreq(int pingFreqMins) {
Log.i("LocationMointor", "LocationMonitor.setLocationUpdateFreq().mode: " + getGpsMode() + "pingFreq:" + pingFreqMins);
//Save new frequency value
SharedPreferences pref = context.getSharedPreferences(PREF_PING_FREQ, Context.MODE_PRIVATE);
Editor prefEditor= pref.edit();
prefEditor.putInt(PREF_PING_FREQ, 10);
prefEditor.commit();
handler.post(new Runnable()
{
public void run() {
//Turn of location updates
if(locationManager !=null)
locationManager.removeUpdates(locationMonitor);
//Restart location updates with new piong frequency
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, MINIMUM_TIME_BETWEEN_UPDATE, MINIMUM_DISTANCECHANGE_FOR_UPDATE,locationMonitor);
}
});
}
public void addUpdateNotify(Object notifyable)
{
this.locationUpdateNotifier = notifyable;
}
public GeoPoint getLastKnownLocation()
{
Criteria crit = new Criteria();
//Try get last known fine location
crit.setAccuracy(Criteria.ACCURACY_FINE);
String provider = locationManager.getBestProvider(crit, false);
Location loc = locationManager.getLastKnownLocation(provider);
//If we got no location, try coarse location
if(loc == null)
{
crit.setAccuracy(Criteria.ACCURACY_COARSE);
provider = locationManager.getBestProvider(crit, false);
loc = locationManager.getLastKnownLocation(provider);
//If nothing, return nothing
if(loc == null)
{
Log.i("LocationMointor", "LocationMonitor.getLastKnownLocation() got no location");
return null;
}
}
//Create geopoint and return it.
GeoPoint geoPoint = new GeoPoint((int)(loc.getLatitude()*1E6),(int)(loc.getLongitude()*1E6));
Log.i("LocationMointor", "LocationMonitor.getLastKnownLocation() got " +geoPoint);
return geoPoint;
}
@Override
public void run() {
running = true;
Object pauser = new Object();
do{
try
{
synchronize();
synchronized(pauser)
{
pauser.wait(UPDATE_FREQ);
}
}
catch(Throwable ex)
{
Log.e("LocationMointor", "LocationMonitor.run() " +ex);
}
}
while(running);
}
public void onCreate() {
super.onCreate();
this.context = this;
this.locationMonitor= this;
handler = new Handler();
//Get the location manager service
locationManager = (LocationManager)context.getSystemService(Context.LOCATION_SERVICE);
//Start gps to get our location
this.locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, UPDATE_FREQ, this);
}
@Override
public void onDestroy() {
super.onDestroy();
kill();
}
@Override
public IBinder onBind(Intent arg0) {
return mBinder;
}
private final IBinder mBinder = new MyBinder();
public class MyBinder extends Binder {
public LocationMonitor getService() {
return LocationMonitor.this;
}
}
}
请你帮我解决这个问题吗？ 提前谢谢。
答案 0 :(得分：2)
与原版Galaxy S手机不同，GS2的GPS工作正常。
从你的代码判断你正在使用getLastKnownLocation并在GPS不可用时回退到Coarse。所以我认为这正是发生的事情： - 你要么是一个非常过时的GPS位置 - 或者是一个粗略的位置，谷歌没有很好地映射你的区域，所以它已经关闭。
您可以通过添加日志或检查提供程序以及从getLastKnownLocation（）获取的非null位置对象的时间戳来检查这些假设。
答案 1 :(得分：0)
如果您检查真实设备上的位置并且您在同一地点停留，我发现自己可以从位置稍微改变一下（您也会在GPS软件中看到这一点，但不知道您正在寻找什么方向在你开车/搬家之前）。因此，位置可能略有变化，但通常不会达到50公里。您是否有其他设备可以测试它是否依赖设备来解决50公里的问题？