Android上的LocationManager API似乎对一个只需要偶尔粗略估计用户位置的应用程序来说有点麻烦。
我正在开发的应用程序本身并不是一个定位应用程序，但它确实需要获取用户的位置，以便显示附近企业的列表。它不需要担心用户是否在移动或类似的事情。
以下是我想做的：
向用户显示附近位置的列表。预加载用户的位置，以便在“活动X”中需要它时，它将可用。我并不特别关心更新的准确性或频率。只要不太远，只要抓住一个位置就足够了。也许如果我想变得更漂亮，我会每隔几分钟左右更新一次位置，但这不是一个很大的优先事项。适用于任何具有GPS或网络位置提供商的设备。
这似乎并不难，但在我看来，我必须组建两个不同的位置提供商（GPS和NETWORK），并管理每个提供商的生命周期。不仅如此，我还必须在多个活动中复制相同的代码以满足#2。过去，我曾尝试使用getBestProvider（）将解决方案简化为仅使用一个位置提供程序，但这似乎只提供了最好的“理论”提供程序，而不是实际会为您提供最佳结果的提供程序。
有没有更简单的方法来实现这一点？
当前回答
我不确定基于位置的服务是否可以从GPS以外的其他基础设施获取位置，但根据那篇文章，这似乎是可能的：
应用程序可以调用几种类型的定位方法。使用移动电话网络：当前单元格ID可用于识别基站收发信机（BTS）设备正在通信以及该BTS的位置。显然，这种方法的准确性取决于单元格的大小，以及可能非常不准确。GSM蜂窝可以是2到20直径千米。另外与细胞ID一起使用的技术可以精度在150米以内。使用卫星：全球定位系统（GPS），受控美国国防部使用由24颗卫星组成的星座围绕地球运行。GPS确定通过计算设备的位置时间差信号来自不同的卫星到达接受者GPS信号是编码的，所以移动设备必须配备使用GPS接收器。GPS是可能是最准确的方法（如果GPS接收机具有清晰的天空视图），但它也有一些缺点：硬件可能很昂贵电池使用时，需要冷启动后的热身对可见卫星的初步定位。它还受到“峡谷效应”的影响在城市，卫星能见度是间歇性的。使用短程定位信标：相对小面积，如单个建筑，局域网可以提供其他位置服务。例如，适当地配备的设备可以使用蓝牙短程定位。
其他回答
要获取并显示用户的当前位置，还可以使用MyLocationOverlay。假设您的活动中有一个mapView字段。要显示用户位置，只需执行以下操作：
myLocationOverlay = new MyLocationOverlay(this, mapView);
myLocationOverlay.enableMyLocation();
mapView.getOverlays().add(myLocationOverlay);
这将从GPS或网络获取当前位置。如果两者都失败，enableMyLocation（）将返回false。
至于该区域周围事物的位置，ItemizedOverlay应该可以做到这一点。
我希望我没有误解你的问题。祝你好运
使用Fedor的解决方案，我经历了多次执行回调gotLocation。当gotLocation方法“足够长”时，这似乎是由于重写的LocationListener.onLocationChanged方法中的竞争条件所致。我不确定，但我猜removeUpdates会阻止Looper队列中新消息的入队，但它不会删除那些已经入队但尚未使用的消息。这就是比赛条件。
为了减少这种错误行为的可能性，可以在激发onLocationChanged事件之前调用removeUpdates，但我们仍然有竞争条件。
我找到的最佳解决方案是用requestSingleUpdate替换requestLocationUpdates。
这是我的版本，基于Fedor的解决方案，使用Handler向looper线程发送消息：
public class LocationResolver {
private Timer timer;
private LocationManager locationManager;
private LocationResult locationResult;
private boolean gpsEnabled = false;
private boolean networkEnabled = false;
private Handler locationTimeoutHandler;
private final Callback locationTimeoutCallback = new Callback() {
public boolean handleMessage(Message msg) {
locationTimeoutFunc();
return true;
}
private void locationTimeoutFunc() {
locationManager.removeUpdates(locationListenerGps);
locationManager.removeUpdates(locationListenerNetwork);
Location networkLocation = null, gpsLocation = null;
if (gpsEnabled)
gpsLocation = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (networkEnabled)
networkLocation = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
// if there are both values use the latest one
if (gpsLocation != null && networkLocation != null) {
if (gpsLocation.getTime() > networkLocation.getTime())
locationResult.gotLocation(gpsLocation);
else
locationResult.gotLocation(networkLocation);
return;
}
if (gpsLocation != null) {
locationResult.gotLocation(gpsLocation);
return;
}
if (networkLocation != null) {
locationResult.gotLocation(networkLocation);
return;
}
locationResult.gotLocation(null);
}
};
private final LocationListener locationListenerGps = new LocationListener() {
public void onLocationChanged(Location location) {
timer.cancel();
locationResult.gotLocation(location);
locationManager.removeUpdates(this);
locationManager.removeUpdates(locationListenerNetwork);
}
public void onProviderDisabled(String provider) {
}
public void onProviderEnabled(String provider) {
}
public void onStatusChanged(String provider, int status, Bundle extras) {
}
};
private final LocationListener locationListenerNetwork = new LocationListener() {
public void onLocationChanged(Location location) {
timer.cancel();
locationResult.gotLocation(location);
locationManager.removeUpdates(this);
locationManager.removeUpdates(locationListenerGps);
}
public void onProviderDisabled(String provider) {
}
public void onProviderEnabled(String provider) {
}
public void onStatusChanged(String provider, int status, Bundle extras) {
}
};
public void prepare() {
locationTimeoutHandler = new Handler(locationTimeoutCallback);
}
public synchronized boolean getLocation(Context context, LocationResult result, int maxMillisToWait) {
locationResult = result;
if (locationManager == null)
locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
// exceptions will be thrown if provider is not permitted.
try {
gpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
} catch (Exception ex) {
}
try {
networkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
} catch (Exception ex) {
}
// don't start listeners if no provider is enabled
if (!gpsEnabled && !networkEnabled)
return false;
if (gpsEnabled)
locationManager.requestSingleUpdate(LocationManager.GPS_PROVIDER, locationListenerGps, Looper.myLooper());
//locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListenerGps);
if (networkEnabled)
locationManager.requestSingleUpdate(LocationManager.NETWORK_PROVIDER, locationListenerNetwork, Looper.myLooper());
//locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListenerNetwork);
timer = new Timer();
timer.schedule(new GetLastLocationTask(), maxMillisToWait);
return true;
}
private class GetLastLocationTask extends TimerTask {
@Override
public void run() {
locationTimeoutHandler.sendEmptyMessage(0);
}
}
public static abstract class LocationResult {
public abstract void gotLocation(Location location);
}
}
我从定制的looper线程中使用这个类，如下所示：
public class LocationGetter {
private final Context context;
private Location location = null;
private final Object gotLocationLock = new Object();
private final LocationResult locationResult = new LocationResult() {
@Override
public void gotLocation(Location location) {
synchronized (gotLocationLock) {
LocationGetter.this.location = location;
gotLocationLock.notifyAll();
Looper.myLooper().quit();
}
}
};
public LocationGetter(Context context) {
if (context == null)
throw new IllegalArgumentException("context == null");
this.context = context;
}
public synchronized Coordinates getLocation(int maxWaitingTime, int updateTimeout) {
try {
final int updateTimeoutPar = updateTimeout;
synchronized (gotLocationLock) {
new Thread() {
public void run() {
Looper.prepare();
LocationResolver locationResolver = new LocationResolver();
locationResolver.prepare();
locationResolver.getLocation(context, locationResult, updateTimeoutPar);
Looper.loop();
}
}.start();
gotLocationLock.wait(maxWaitingTime);
}
} catch (InterruptedException e1) {
e1.printStackTrace();
}
if (location != null)
coordinates = new Coordinates(location.getLatitude(), location.getLongitude());
else
coordinates = Coordinates.UNDEFINED;
return coordinates;
}
}
其中Coordinates是一个简单的类，具有两个财产：纬度和经度。
对@Fedor解决方案的改进。我们可以使用位置管理器的requestSingleUpdate方法，而不是使用“0”时间间隔和“0”距离请求位置。更新的代码（kotlin版本）
import android.annotation.SuppressLint
import android.content.Context
import android.location.Criteria
import android.location.Location
import android.location.LocationListener
import android.location.LocationManager
import android.os.Bundle
import java.util.*
@SuppressLint("MissingPermission")
class AppLocationProvider {
private lateinit var timer: Timer
private var locationManager: LocationManager? = null
private lateinit var locationCallBack: LocationCallBack
private var gpsEnabled = false
private var networkEnabled = false
private var locationListener: LocationListener = object : LocationListener {
override fun onLocationChanged(location: Location) {
timer.cancel()
locationCallBack.locationResult(location)
}
override fun onProviderDisabled(provider: String) {}
override fun onProviderEnabled(provider: String) {}
override fun onStatusChanged(provider: String, status: Int, extras: Bundle) {}
}
fun getLocation(context : Context, callBack: LocationCallBack): Boolean {
locationCallBack = callBack
if (locationManager == null)
locationManager = context.getSystemService(Context.LOCATION_SERVICE) as LocationManager?
//exceptions will be thrown if provider is not permitted.
try {
gpsEnabled = locationManager!!.isProviderEnabled(LocationManager.GPS_PROVIDER)
} catch (ex: Exception) {
ex.printStackTrace()
}
try {
networkEnabled = locationManager!!.isProviderEnabled(LocationManager.NETWORK_PROVIDER)
} catch (ex: Exception) {
ex.printStackTrace()
}
//don't start listeners if no provider is enabled
if (!gpsEnabled && !networkEnabled)
return false
val criteria = Criteria()
if (gpsEnabled) {
criteria.accuracy = Criteria.ACCURACY_FINE
} else {
criteria.accuracy = Criteria.ACCURACY_COARSE
}
locationManager!!.requestSingleUpdate(criteria, locationListener, null)
timer = Timer()
timer.schedule(GetLastKnownLocation(), 5000)
return true
}
inner class GetLastKnownLocation : TimerTask() {
override fun run() {
locationManager!!.removeUpdates(locationListener)
var netLoc: Location? = null
var gpsLoc: Location? = null
if (gpsEnabled)
gpsLoc = locationManager!!.getLastKnownLocation(LocationManager.GPS_PROVIDER)
if (networkEnabled)
netLoc = locationManager!!.getLastKnownLocation(LocationManager.NETWORK_PROVIDER)
//check which value use the latest one
if (gpsLoc != null && netLoc != null) {
if (gpsLoc.time > netLoc.time)
locationCallBack.locationResult(gpsLoc)
else
locationCallBack.locationResult(netLoc)
return
}
if (gpsLoc != null) {
locationCallBack.locationResult(gpsLoc)
return
}
if (netLoc != null) {
locationCallBack.locationResult(netLoc)
return
}
locationCallBack.locationResult(null)
}
}
interface LocationCallBack {
fun locationResult(location: Location?)
}
}
要获取位置，只需调用getLocation方法-
AppLocationProvider().getLocation(context, object : AppLocationProvider.LocationCallBack {
override fun locationResult(location: Location?) {
// use location, this might get called in a different thread if a location is a last known location. In that case, you can post location on main thread
}
})
注：在调用getLocation方法之前，必须授予所需的位置权限。
在过去一年多的时间里，我使用GPS_PROVIDER和NETWORK_PROVIDER的组合来获取当前位置，它运行得很好，但从过去几个月开始，我在经过长时间的延迟后才获取位置，所以我改用了最新的API FusedLocationProviderClient，它运行的很好。
下面是我使用FusedLocationProviderClient编写的获取当前位置的类。在下面的代码中，我使用了一个计时器等待一段时间以获取当前位置，我安排了计时器15秒的延迟，您可以根据您的情况进行更改。
private static FusedLocationService ourInstance;
private final LocationRequest locationRequest;
private FusedLocationProviderClient mFusedLocationClient;
private Location mLastLocation;
private Context context;
private FindOutLocation findOutLocation;
private boolean callbackTriggered = false;
private Timer timer;
public static FusedLocationService getInstance(Context pContext) {
if (null == ourInstance) ourInstance = new FusedLocationService(pContext);
return ourInstance;
}
private FusedLocationService(Context pContext) {
context = pContext;
mFusedLocationClient = LocationServices.getFusedLocationProviderClient(context);
locationRequest = getLocationRequest();
requestLocation(context);
}
public Location getLastKnownLocation() {
return mLastLocation;
}
private void requestLocation(Context context) {
if (ActivityCompat.checkSelfPermission(context, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(context, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
return;
}
mFusedLocationClient.requestLocationUpdates(locationRequest, mLocationCallback, null);
mFusedLocationClient.getLastLocation().addOnSuccessListener(location -> {
if (location != null) {
mLastLocation = location;
triggerCallback(mLastLocation);
}
});
}
private LocationRequest getLocationRequest() {
LocationRequest locationRequest = new LocationRequest();
long INTERVAL = 10 * 1000;
long FASTEST_INTERVAL = 5 * 1000;
locationRequest.setInterval(INTERVAL);
locationRequest.setFastestInterval(FASTEST_INTERVAL);
locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
return locationRequest;
}
private LocationCallback mLocationCallback = new LocationCallback() {
@Override
public void onLocationResult(LocationResult locationResult) {
for (Location location : locationResult.getLocations()) {
if (location != null) mLastLocation = location;
}
if (null != mLastLocation) triggerCallback(mLastLocation);
}
};
public static abstract class FindOutLocation {
public abstract void gotLocation(Location location);
}
@SuppressLint("MissingPermission")
public void findLocation(FindOutLocation findOutLocation) {
long TIMER_TIME_OUT = 15 * 1000;
this.findOutLocation = findOutLocation;
callbackTriggered = false;
try {
requestLocation(context);
timer = new Timer();
timer.schedule(new GetLastLocation(context), TIMER_TIME_OUT);
} catch (Exception e) {
e.printStackTrace();
}
}
private class GetLastLocation extends TimerTask {
Context context;
GetLastLocation(Context context) {
this.context = context;
}
@Override
public void run() {
triggerCallback(mLastLocation);
}
}
private void triggerCallback(Location location) {
if (null != location) mLastLocation = location;
if (!callbackTriggered && null != findOutLocation) {
callbackTriggered = true;
removeLocationUpdates();
findOutLocation.gotLocation(location);
findOutLocation = null;
}
}
private void removeLocationUpdates() {
if (null != timer) timer.cancel();
if (null != mFusedLocationClient)
mFusedLocationClient.removeLocationUpdates(mLocationCallback);
}
}
这是从活动中调用的，下面是代码
FusedLocationService.FindOutLocation findOutLocation = new FusedLocationService.FindOutLocation() {
@Override
public void gotLocation(Location currentLocation) {
if (currentLocation != null) {
/*TODO DO SOMETHING WITH CURRENT LOCATION*/
}
}
};
FusedLocationService.getInstance(this).findLocation(findOutLocation);
在AndroidManifest.xml中添加以下条目
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<!-- Needed only if your app targets Android 5.0 (API level 21) or higher. -->
<uses-feature android:name="android.hardware.location.gps" />
在Activity Class中创建自定义方法：
private void getTheUserPermission() {
ActivityCompat.requestPermissions(this, new String[]
{Manifest.permission.ACCESS_FINE_LOCATION}, REQUEST_LOCATION);
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
LocationGetter locationGetter = new LocationGetter(FreshMenuSearchActivity.this, REQUEST_LOCATION, locationManager);
if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
locationGetter.OnGPS();
} else {
locationGetter.getLocation();
}
}
生成用户定义的类名LocationGetter：-
public class LocationGetter {
private int REQUEST_LOCATION;
private FreshMenuSearchActivity mContext;
private LocationManager locationManager;
private Geocoder geocoder;
public LocationGetter(FreshMenuSearchActivity mContext, int requestLocation, LocationManager locationManager) {
this.mContext = mContext;
this.locationManager = locationManager;
this.REQUEST_LOCATION = requestLocation;
}
public void getLocation() {
if (ActivityCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(mContext,
Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(mContext, new String[]
{Manifest.permission.ACCESS_FINE_LOCATION}, REQUEST_LOCATION);
} else {
Location LocationGps = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
Location LocationNetwork = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
Location LocationPassive = locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
if (LocationGps != null) {
double lat = LocationGps.getLatitude();
double longi = LocationGps.getLongitude();
getTheAddress(lat, longi);
} else if (LocationNetwork != null) {
double lat = LocationNetwork.getLatitude();
double longi = LocationNetwork.getLongitude();
getTheAddress(lat, longi);
} else if (LocationPassive != null) {
double lat = LocationPassive.getLatitude();
double longi = LocationPassive.getLongitude();
getTheAddress(lat, longi);
} else {
Toast.makeText(mContext, "Can't Get Your Location", Toast.LENGTH_SHORT).show();
}
}
}
private void getTheAddress(double latitude, double longitude) {
List<Address> addresses;
geocoder = new Geocoder(mContext, Locale.getDefault());
try {
addresses = geocoder.getFromLocation(latitude, longitude, 1);
String address = addresses.get(0).getAddressLine(0);
String city = addresses.get(0).getLocality();
String state = addresses.get(0).getAdminArea();
String country = addresses.get(0).getCountryName();
String postalCode = addresses.get(0).getPostalCode();
String knownName = addresses.get(0).getFeatureName();
Log.d("neel", address);
} catch (IOException e) {
e.printStackTrace();
}
}
public void OnGPS() {
final AlertDialog.Builder builder = new AlertDialog.Builder(mContext);
builder.setMessage("Enable GPS").setCancelable(false).setPositiveButton("YES", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
mContext.startActivity(new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS));
}
}).setNegativeButton("NO", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
final AlertDialog alertDialog = builder.create();
alertDialog.show();
}
}
