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
在android系统中获取位置更新需要很多东西，需要大量的bolierplate代码。
你需要照顾好
Google Play服务可用性检查，更新Google play服务，如果它是旧的或不可用GoogleApiClient的对话框创建及其连接、断开等回调。停止并释放用于位置更新的资源处理位置权限方案检查位置服务是否打开或关闭获取最新位置也不是那么容易如果在一定时间后未找到位置，则回退到最后一个已知位置
我已经创建了Android EasyLocation（小型Android库），它将处理所有这些事情，您可以专注于业务逻辑。
您只需要扩展EasyLocationActivity
requestSingleLocationFix(easyLocationRequest);
or
requestLocationUpdates(easyLocationRequest);
点击此处查看示例应用程序和所需步骤https://github.com/akhgupta/Android-EasyLocation
其他回答
实际上，我们可以使用两个提供商（GPS和网络）。他们只是分享一个公共听众：
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 10 * 1000, (float) 10.0, listener);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 90 * 1000, (float) 10.0, listener);
这是必要的，因为总是需要及时调用OnLocationChanged（）方法。
public static Location getBestLocation(Context ctxt) {
Location gpslocation = getLocationByProvider(
LocationManager.GPS_PROVIDER, ctxt);
Location networkLocation = getLocationByProvider(
LocationManager.NETWORK_PROVIDER, ctxt);
Location fetchedlocation = null;
// if we have only one location available, the choice is easy
if (gpslocation != null) {
Log.i("New Location Receiver", "GPS Location available.");
fetchedlocation = gpslocation;
} else {
Log.i("New Location Receiver",
"No GPS Location available. Fetching Network location lat="
+ networkLocation.getLatitude() + " lon ="
+ networkLocation.getLongitude());
fetchedlocation = networkLocation;
}
return fetchedlocation;
}
/**
* get the last known location from a specific provider (network/gps)
*/
private static Location getLocationByProvider(String provider, Context ctxt) {
Location location = null;
// if (!isProviderSupported(provider)) {
// return null;
// }
LocationManager locationManager = (LocationManager) ctxt
.getSystemService(Context.LOCATION_SERVICE);
try {
if (locationManager.isProviderEnabled(provider)) {
location = locationManager.getLastKnownLocation(provider);
}
} catch (IllegalArgumentException e) {
Log.i("New Location Receiver", "Cannot access Provider " + provider);
}
return location;
}
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。
使用以下代码，它将提供可用的最佳提供商：
String locCtx = Context.LOCATION_SERVICE;
LocationManager locationMgr = (LocationManager) ctx.getSystemService(locCtx);
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setAltitudeRequired(false);
criteria.setBearingRequired(false);
criteria.setCostAllowed(true);
criteria.setPowerRequirement(Criteria.POWER_LOW);
String provider = locationMgr.getBestProvider(criteria, true);
System.out.println("Best Available provider::::"+provider);
在搜索了如何获得最佳精确用户位置的最佳实现后，我成功地结合了所有最佳方法，并提出了以下类：
/**
* Retrieve accurate location from GPS or network services.
*
*
* Class usage example:
*
* public void onCreate(Bundle savedInstanceState) {
* ...
* my_location = new MyLocation();
* my_location.init(main.this, locationResult);
* }
*
*
* public LocationResult locationResult = new LocationResult(){
* @Override
* public void gotLocation(final Location location){
* // do something
* location.getLongitude();
* location.getLatitude();
* }
* };
*/
class MyLocation{
/**
* If GPS is enabled.
* Use minimal connected satellites count.
*/
private static final int min_gps_sat_count = 5;
/**
* Iteration step time.
*/
private static final int iteration_timeout_step = 500;
LocationResult locationResult;
private Location bestLocation = null;
private Handler handler = new Handler();
private LocationManager myLocationManager;
public Context context;
private boolean gps_enabled = false;
private int counts = 0;
private int sat_count = 0;
private Runnable showTime = new Runnable() {
public void run() {
boolean stop = false;
counts++;
System.println("counts=" + counts);
//if timeout (1 min) exceeded, stop tying
if(counts > 120){
stop = true;
}
//update last best location
bestLocation = getLocation(context);
//if location is not ready or don`t exists, try again
if(bestLocation == null && gps_enabled){
System.println("BestLocation not ready, continue to wait");
handler.postDelayed(this, iteration_timeout_step);
}else{
//if best location is known, calculate if we need to continue to look for better location
//if gps is enabled and min satellites count has not been connected or min check count is smaller then 4 (2 sec)
if(stop == false && !needToStop()){
System.println("Connected " + sat_count + " sattelites. continue waiting..");
handler.postDelayed(this, iteration_timeout_step);
}else{
System.println("#########################################");
System.println("BestLocation found return result to main. sat_count=" + sat_count);
System.println("#########################################");
// removing all updates and listeners
myLocationManager.removeUpdates(gpsLocationListener);
myLocationManager.removeUpdates(networkLocationListener);
myLocationManager.removeGpsStatusListener(gpsStatusListener);
sat_count = 0;
// send best location to locationResult
locationResult.gotLocation(bestLocation);
}
}
}
};
/**
* Determine if continue to try to find best location
*/
private Boolean needToStop(){
if(!gps_enabled){
return true;
}
else if(counts <= 4){
return false;
}
if(sat_count < min_gps_sat_count){
//if 20-25 sec and 3 satellites found then stop
if(counts >= 40 && sat_count >= 3){
return true;
}
return false;
}
}
return true;
}
/**
* Best location abstract result class
*/
public static abstract class LocationResult{
public abstract void gotLocation(Location location);
}
/**
* Initialize starting values and starting best location listeners
*
* @param Context ctx
* @param LocationResult result
*/
public void init(Context ctx, LocationResult result){
context = ctx;
locationResult = result;
myLocationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
gps_enabled = (Boolean) myLocationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
bestLocation = null;
counts = 0;
// turning on location updates
myLocationManager.requestLocationUpdates("network", 0, 0, networkLocationListener);
myLocationManager.requestLocationUpdates("gps", 0, 0, gpsLocationListener);
myLocationManager.addGpsStatusListener(gpsStatusListener);
// starting best location finder loop
handler.postDelayed(showTime, iteration_timeout_step);
}
/**
* GpsStatus listener. OnChainged counts connected satellites count.
*/
public final GpsStatus.Listener gpsStatusListener = new GpsStatus.Listener() {
public void onGpsStatusChanged(int event) {
if(event == GpsStatus.GPS_EVENT_SATELLITE_STATUS){
try {
// Check number of satellites in list to determine fix state
GpsStatus status = myLocationManager.getGpsStatus(null);
Iterable<GpsSatellite>satellites = status.getSatellites();
sat_count = 0;
Iterator<GpsSatellite>satI = satellites.iterator();
while(satI.hasNext()) {
GpsSatellite satellite = satI.next();
System.println("Satellite: snr=" + satellite.getSnr() + ", elevation=" + satellite.getElevation());
sat_count++;
}
} catch (Exception e) {
e.printStackTrace();
sat_count = min_gps_sat_count + 1;
}
System.println("#### sat_count = " + sat_count);
}
}
};
/**
* Gps location listener.
*/
public final LocationListener gpsLocationListener = new LocationListener(){
@Override
public void onLocationChanged(Location location){
}
public void onProviderDisabled(String provider){}
public void onProviderEnabled(String provider){}
public void onStatusChanged(String provider, int status, Bundle extras){}
};
/**
* Network location listener.
*/
public final LocationListener networkLocationListener = new LocationListener(){
@Override
public void onLocationChanged(Location location){
}
public void onProviderDisabled(String provider){}
public void onProviderEnabled(String provider){}
public void onStatusChanged(String provider, int status, Bundle extras){}
};
/**
* Returns best location using LocationManager.getBestProvider()
*
* @param context
* @return Location|null
*/
public static Location getLocation(Context context){
System.println("getLocation()");
// fetch last known location and update it
try {
LocationManager lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setAltitudeRequired(false);
criteria.setBearingRequired(false);
criteria.setCostAllowed(true);
String strLocationProvider = lm.getBestProvider(criteria, true);
System.println("strLocationProvider=" + strLocationProvider);
Location location = lm.getLastKnownLocation(strLocationProvider);
if(location != null){
return location;
}
return null;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
如果启用gps，此类将尝试连接到min_gps_sat_count卫星。Else返回LocationManager.getBestProvider（）位置。检查代码！
