我正在尝试找到一个Android项目的当前位置。加载应用程序时，我的当前位置始终为null。我已经在清单等中设置了权限。当我找到当前位置时，我打算使用坐标来查找到地图上其他位置的距离。我的代码片段如下。为什么我总是得到一个空值？
locMan = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Criteria crit = new Criteria();
towers = locMan.getBestProvider(crit, false);
location = locMan.getLastKnownLocation(towers);
if (location != null) {
System.out.println("Location is not null!");
lat = (int) (location.getLatitude() *1E6);
longi = (int) (location.getLongitude() * 1E6);
GeoPoint ourLocation = new GeoPoint(lati, longi);
OverlayItem overlayItem = new OverlayItem(ourLocation, "1st String",
"2nd String");
CustomPinpoint custom = new CustomPinpoint(d, MainMap.this);
custom.insertPinpoint(overlayItem);
overlayList.add(custom);
overlayList.clear();
} else {
System.out.println("Location is null! " + towers);
Toast.makeText(MainMap.this, "Couldn't get provider",Toast.LENGTH_SHORT)
.show();
}
答案 0 :(得分：35)
getLastKnownLocation()使用之前由其他应用程序找到的位置。如果没有应用程序执行此操作，则getLastKnownLocation()将返回null。
您可以对代码执行一项操作，以便更有可能获得最后已知位置 - 迭代所有已启用的提供程序，而不仅仅是最佳提供程序。例如，
private Location getLastKnownLocation() {
List<String> providers = mLocationManager.getProviders(true);
Location bestLocation = null;
for (String provider : providers) {
Location l = mLocationManager.getLastKnownLocation(provider);
ALog.d("last known location, provider: %s, location: %s", provider,
l);
if (l == null) {
continue;
}
if (bestLocation == null
|| l.getAccuracy() < bestLocation.getAccuracy()) {
ALog.d("found best last known location: %s", l);
bestLocation = l;
}
}
if (bestLocation == null) {
return null;
}
return bestLocation;
}
如果您的应用无法在没有位置的情况下进行交易，并且如果没有最后的已知位置，则需要监听位置更新。你可以看看这个类的例子，
https://github.com/farble1670/autobright/blob/master/src/org/jtb/autobright/EventService.java
查看方法onStartCommand()，检查网络提供程序是否已启用。如果没有，它使用最后已知的位置。如果已启用，则会注册以接收位置更新。
答案 1 :(得分：8)
如果您在主类中使用以下方法找到设备的当前位置
public void find_Location(Context con) {
Log.d("Find Location", "in find_location");
this.con = con;
String location_context = Context.LOCATION_SERVICE;
locationManager = (LocationManager) con.getSystemService(location_context);
List<String> providers = locationManager.getProviders(true);
for (String provider : providers) {
locationManager.requestLocationUpdates(provider, 1000, 0,
new LocationListener() {
public void onLocationChanged(Location location) {}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status,
Bundle extras) {}
});
Location location = locationManager.getLastKnownLocation(provider);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
addr = ConvertPointToLocation(latitude, longitude);
String temp_c = SendToUrl(addr);
}
}
}
并在清单文件中添加用户权限方法
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
答案 2 :(得分：0)
试试这个不会给你空当前位置
class GetLastLocation extends TimerTask {
LocationManager mlocManager = (LocationManager)
getSystemService(Context.LOCATION_SERVICE);
LocationListener mlocListenerTmp = new CustomLocationListener();
private final Handler mLocHandler;
public GetLastLocation(Handler mLocHandler) {
this.mLocHandler = mLocHandler;
}
@Override
public void run() {
timer.cancel();
mlocManager.removeUpdates(mlocListenerTmp);
Location location = mlocManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
{
if (mlocListenerTmp != null) {
mlocManager.removeUpdates(mlocListenerTmp);
}
currentLocation = location;
}
if (location != null) {
String message = String.format(
"Location \n Longitude: %1$s \n Latitude: %2$s",
location.getLongitude(), location.getLatitude());
Log.d("loc", " :" + message);
Bundle b = new Bundle();
{
b.putBoolean("locationRetrieved", true);
{
Message msg = Message.obtain();
{
msg.setData(b);
mLocHandler.sendMessage(msg);
}
}
}
} else {
Log.d(
"loc",
":No GPS or network signal please fill the location manually!");
location = mlocManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
currentLocation = location;
Bundle b = new Bundle();
{
b.putBoolean("locationRetrieved", true);
{
Message msg = Message.obtain();
{
msg.setData(b);
mLocHandler.sendMessage(msg);
}
}
}
} else {
Bundle b = new Bundle();
{
b.putBoolean("locationRetrieved", false);
{
Message msg = Message.obtain();
{
msg.setData(b);
mLocHandler.sendMessage(msg);
}
}
}
}
}
}
}
像这样称呼它
timer.schedule(new GetLastLocation(mLocHandler), 3000);
和customLocationclass如下
public class CustomLocationListener implements LocationListener {
@Override
public void onLocationChanged(Location loc) {
loc.getLatitude();
loc.getLongitude();
currentLocation = loc;
String Text = "My current location is: " + "Latitud = "
+ loc.getLatitude() + "Longitud = " + loc.getLongitude();
Log.d("loc", "onLocationChanged" + Text);
}
@Override
public void onProviderDisabled(String provider) {}
@Override
public void onProviderEnabled(String provider) {}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {}
}
答案 3 :(得分：0)
如果您在marshmallow设备中试用它，请尝试手动为您的应用启用位置权限。
答案 4 :(得分：0)
使用以下方法打开您的GPS。它可以帮助您显示当前位置，而不会出现任何错误。在onCreate中调用它
public void displayLocationSettingsRequest(Context context, int requestCode) {
GoogleApiClient googleApiClient = new GoogleApiClient.Builder(context)
.addApi(LocationServices.API).build();
googleApiClient.connect();
LocationRequest locationRequest = LocationRequest.create();
locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
locationRequest.setInterval(10000);
locationRequest.setFastestInterval(10000 / 2);
LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder().addLocationRequest(locationRequest);
builder.setAlwaysShow(true);
PendingResult<LocationSettingsResult> result = LocationServices.SettingsApi.checkLocationSettings(googleApiClient, builder.build());
result.setResultCallback(result1 -> {
final Status status = result1.getStatus();
if (status.getStatusCode() == LocationSettingsStatusCodes.RESOLUTION_REQUIRED)
try {
status.startResolutionForResult((Activity) context, requestCode);
} catch (IntentSender.SendIntentException ignored) {
}
});
答案 5 :(得分：0)
如果您的提供商列表出现空错误，请更改...
List<String> providers = mLocationManager.getProviders(true);
到...
List<String> providers = locationManager.getAllProviders();
这对我有用，请确保您的AndroidManifest.xml文件中包含以下内容...
<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_NETWORK_STATE"/>
答案 6 :(得分：-1)
您是否尝试过反转代码？例如，if（location == null）然后打印该位置为null，否则打印位置不为null。我曾经遇到过这个问题，似乎已经解决了这个问题（我不知道为什么）。试试吧。
如果这不起作用，也许谷歌地图API返回空值，在这种情况下，它是GM-API或调用方法的问题。任何这些都可能是问题。
希望这有帮助，
-JXP