private void requestLocationUpdates(LocationRequest request, LocationListener listener,
            Looper looper, PendingIntent intent) {

        String packageName = mContext.getPackageName();

        // wrap the listener class
        ListenerTransport transport = wrapListener(listener, looper);

        try {
            mService.requestLocationUpdates(request, transport, intent, packageName);
       } catch (RemoteException e) {
           throw e.rethrowFromSystemServer();
       }
}

private int mQuality = POWER_LOW;
private long mInterval = 60 * 60 * 1000;   // 60 minutes
private long mFastestInterval = (long)(mInterval / FASTEST_INTERVAL_FACTOR);  // 10 minutes
private boolean mExplicitFastestInterval = false;
private long mExpireAt = Long.MAX_VALUE;  // no expiry
private int mNumUpdates = Integer.MAX_VALUE;  // no expiry
private float mSmallestDisplacement = 0.0f;    // meters
private WorkSource mWorkSource = null;
private boolean mHideFromAppOps = false; // True if this request shouldn't be counted by AppOps

private String mProvider = LocationManager.FUSED_PROVIDER;  // for deprecated APIs that explicitly request a provider

package android.location;

import android.location.Location;
import android.os.Bundle;

/**
 * {@hide}
 */
oneway interface ILocationListener
{
    void onLocationChanged(in Location location);
    void onStatusChanged(String provider, int status, in Bundle extras);
    void onProviderEnabled(String provider);
    void onProviderDisabled(String provider);
}

      ListenerTransport(LocationListener listener, Looper looper) {
            mListener = listener;

            if (looper == null) {
                mListenerHandler = new Handler() {
                    @Override
                    public void handleMessage(Message msg) {
                        _handleMessage(msg);
                    }
                };
            } else {
                mListenerHandler = new Handler(looper) {
                    @Override
                    public void handleMessage(Message msg) {
                        _handleMessage(msg);
                    }
                };
            }
        }

@Override
public void requestLocationUpdates(LocationRequest request, ILocationListener listener,
            PendingIntent intent, String packageName) {
        ...
        // providers may use public location API's, need to clear identity
        long identity = Binder.clearCallingIdentity();
        try {
            // We don't check for MODE_IGNORED here; we will do that when we go to deliver
            // a location.
            checkLocationAccess(pid, uid, packageName, allowedResolutionLevel);

            synchronized (mLock) {
                Receiver recevier = checkListenerOrIntentLocked(listener, intent, pid, uid,
                        packageName, workSource, hideFromAppOps);
                requestLocationUpdatesLocked(sanitizedRequest, recevier, pid, uid, packageName);
            }
        } finally {
            Binder.restoreCallingIdentity(identity);
        }
}

private void requestLocationUpdatesLocked(LocationRequest request, Receiver receiver,
            int pid, int uid, String packageName) {
        // Figure out the provider. Either its explicitly request (legacy use cases), or
        // use the fused provider
        if (request == null) request = DEFAULT_LOCATION_REQUEST;
        String name = request.getProvider();
    
        ...

        boolean isProviderEnabled = isAllowedByUserSettingsLocked(name, uid);
        if (isProviderEnabled) {
            applyRequirementsLocked(name);
        } else {
            // Notify the listener that updates are currently disabled
            receiver.callProviderEnabledLocked(name, false);
        }
        // Update the monitoring here just in case multiple location requests were added to the
        // same receiver (this request may be high power and the initial might not have been).
        receiver.updateMonitoring(true);
    }

 private class UpdateRecord {
        final String mProvider;
        final LocationRequest mRealRequest;  // original request from client
        LocationRequest mRequest;  // possibly throttled version of the request
        final Receiver mReceiver;
        boolean mIsForegroundUid;
        Location mLastFixBroadcast;
        long mLastStatusBroadcast;
        ...
 }

 private void applyRequirementsLocked(String provider) {
        ...

        if (records != null) {
            for (UpdateRecord record : records) {
                if (isCurrentProfile(UserHandle.getUserId(record.mReceiver.mIdentity.mUid))) {
                    if (checkLocationAccess(
                            record.mReceiver.mIdentity.mPid,
                            record.mReceiver.mIdentity.mUid,
                            record.mReceiver.mIdentity.mPackageName,
                            record.mReceiver.mAllowedResolutionLevel)) {
                        LocationRequest locationRequest = record.mRealRequest;
                        long interval = locationRequest.getInterval();

                        if (!isThrottlingExemptLocked(record.mReceiver.mIdentity)) {
                            if (!record.mIsForegroundUid) {
                                interval = Math.max(interval, backgroundThrottleInterval);
                            }
                            if (interval != locationRequest.getInterval()) {
                                locationRequest = new LocationRequest(locationRequest);
                                locationRequest.setInterval(interval);
                            }
                        }

                        record.mRequest = locationRequest;
                        providerRequest.locationRequests.add(locationRequest);
                        if (interval < providerRequest.interval) {
                            providerRequest.reportLocation = true;
                            providerRequest.interval = interval;
                        }
                    }
                }
            }

            if (providerRequest.reportLocation) {
                ...
            }
        }
        ...
         p.setRequest(providerRequest, worksource);
    }

    @Override
    public void setRequest(ProviderRequest request, WorkSource source) {
        sendMessage(SET_REQUEST, 0, new GpsRequest(request, source));
    }

        @Override
        public void handleMessage(Message msg) {
            int message = msg.what;
            switch (message) {
                case ENABLE:
                    if (msg.arg1 == 1) {
                        handleEnable();
                    } else {
                        handleDisable();
                    }
                    break;
                case SET_REQUEST:
                    GpsRequest gpsRequest = (GpsRequest) msg.obj;
                    handleSetRequest(gpsRequest.request, gpsRequest.source);
                    break;
                case UPDATE_NETWORK_STATE:
                    handleUpdateNetworkState((Network) msg.obj);
                    break;
                case REQUEST_SUPL_CONNECTION:
                    handleRequestSuplConnection((InetAddress) msg.obj);
                    break;
                case RELEASE_SUPL_CONNECTION:
                    handleReleaseSuplConnection(msg.arg1);
                    break;
                case INJECT_NTP_TIME:
                    handleInjectNtpTime();
                    break;
                case DOWNLOAD_XTRA_DATA:
                    handleDownloadXtraData();
                    break;
                case INJECT_NTP_TIME_FINISHED:
                    mInjectNtpTimePending = STATE_IDLE;
                    break;
                case DOWNLOAD_XTRA_DATA_FINISHED:
                    mDownloadXtraDataPending = STATE_IDLE;
                    break;
                case UPDATE_LOCATION:
                    handleUpdateLocation((Location) msg.obj);
                    break;
                case SUBSCRIPTION_OR_SIM_CHANGED:
                    subscriptionOrSimChanged(mContext);
                    break;
                case INITIALIZE_HANDLER:
                    handleInitialize();
                    break;
            }
            if (msg.arg2 == 1) {
                // wakelock was taken for this message, release it
                mWakeLock.release();
                if (Log.isLoggable(TAG, Log.INFO)) {
                    Log.i(TAG, "WakeLock released by handleMessage(" + messageIdAsString(message)
                            + ", " + msg.arg1 + ", " + msg.obj + ")");
                }
            }
        }

    @Override
    public void setRequest(ProviderRequest request, WorkSource source) {
        synchronized (mLock) {
            mRequest = request;
            mWorksource = source;
        }
        ILocationProvider service = getService();
        if (service == null) return;

        try {
            service.setRequest(request, source);
        } catch (RemoteException e) {
            Log.w(TAG, e);
        } catch (Exception e) {
            // never let remote service crash system server
            Log.e(TAG, "Exception from " + mServiceWatcher.getBestPackageName(), e);
        }
    }

private Runnable mNewServiceWork = new Runnable() {
        @Override
        public void run() {
            if (D) Log.d(TAG, "applying state to connected service");

            boolean enabled;
            ProviderProperties properties = null;
            ProviderRequest request;
            WorkSource source;
            ILocationProvider service;
            synchronized (mLock) {
                enabled = mEnabled;
                request = mRequest;
                source = mWorksource;
                service = getService();
            }

            if (service == null) return;

            try {
                // load properties from provider
                properties = service.getProperties();
                if (properties == null) {
                    Log.e(TAG, mServiceWatcher.getBestPackageName() +
                            " has invalid locatino provider properties");
                }

                // apply current state to new service
                if (enabled) {
                    service.enable();
                    if (request != null) {
                        service.setRequest(request, source);
                    }
                }
            } catch (RemoteException e) {
                Log.w(TAG, e);
            } catch (Exception e) {
                // never let remote service crash system server
                Log.e(TAG, "Exception from " + mServiceWatcher.getBestPackageName(), e);
            }

            synchronized (mLock) {
                mProperties = properties;
            }
        }
    };

    private static final ProviderProperties PROPERTIES = new ProviderProperties(
            true, true, false, false, true, true, true,
            Criteria.POWER_HIGH, Criteria.ACCURACY_FINE);

public abstract class LocationProviderBase {
    ...
        private final class Service extends ILocationProvider.Stub {
        @Override
        public void enable() {
            onEnable();
        }
        @Override
        public void disable() {
            onDisable();
        }
        @Override
        public void setRequest(ProviderRequest request, WorkSource ws) {
            onSetRequest(new ProviderRequestUnbundled(request), ws);
        }
        @Override
        public ProviderProperties getProperties() {
            return mProperties;
        }
        @Override
        public int getStatus(Bundle extras) {
            return onGetStatus(extras);
        }
        @Override
        public long getStatusUpdateTime() {
            return onGetStatusUpdateTime();
        }
        @Override
        public boolean sendExtraCommand(String command, Bundle extras) {
            return onSendExtraCommand(command, extras);
        }
        @Override
        public void dump(FileDescriptor fd, String[] args) {
            PrintWriter pw = new FastPrintWriter(new FileOutputStream(fd));
            onDump(fd, pw, args);
            pw.flush();
        }
    }
    public final void reportLocation(Location location) {
        try {
            mLocationManager.reportLocation(location, false);
        } catch (RemoteException e) {
            Log.e(TAG, "RemoteException", e);
        } catch (Exception e) {
            // never crash provider, might be running in a system process
            Log.e(TAG, "Exception", e);
        }
    }
    ...
    public abstract void onSetRequest(ProviderRequestUnbundled request, WorkSource source);
    ...
    public abstract int onGetStatus(Bundle extras);
    public abstract long onGetStatusUpdateTime();
...
}

ProviderPropertiesUnbundled PROPERTIES = ProviderPropertiesUnbundled.create(
            false, false, false, false, true, true, true, Criteria.POWER_LOW,
            Criteria.ACCURACY_FINE);

   /**
     * Test whether one location (a) is better to use than another (b).
     */
    private static boolean isBetterThan(Location locationA, Location locationB) {
      if (locationA == null) {
        return false;
      }
      if (locationB == null) {
        return true;
      }
      // A provider is better if the reading is sufficiently newer.  Heading
      // underground can cause GPS to stop reporting fixes.  In this case it's
      // appropriate to revert to cell, even when its accuracy is less.
      if (locationA.getElapsedRealtimeNanos() > locationB.getElapsedRealtimeNanos() + SWITCH_ON_FRESHNESS_CLIFF_NS) {
        return true;
      }

      // A provider is better if it has better accuracy.  Assuming both readings
      // are fresh (and by that accurate), choose the one with the smaller
      // accuracy circle.
      if (!locationA.hasAccuracy()) {
        return false;
      }
      if (!locationB.hasAccuracy()) {
        return true;
      }
      return locationA.getAccuracy() < locationB.getAccuracy();
    }