Android GPS learning (2): GPS service startup and initialization process

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1. Start GPS service

The code to add the LocationManagerService method to the startOtherServices method of SystemServer.java is as follows,

frameworks/base/services/java/com/android/server/SystemServer.java

traceBeginAndSlog("StartLocationManagerService");
try {
    
    
    location = new LocationManagerService(context);
    ServiceManager.addService(Context.LOCATION_SERVICE, location);

After adding the gps service to the system, in the startOtherServices method of SystemServer.java

final LocationManagerService locationF = location;

try {
    
    
    if (locationF != null) locationF.systemRunning();

Call the systemRunning method of LocationManagerService to complete the initialization of LocationManagerService.

2. Function call

frameworks/base/services/core/java/com/android/server/LocationManagerService.java

The loadProvidersLocked method will be called in the systemRunning method,

public void systemRunning() {
    
    
    synchronized (mLock) {
    
    
        // prepare providers
        loadProvidersLocked();
        updateProvidersLocked();
    }

The loadProvidersLocked method is mainly to add GPS positioning providers supported on the device,

private void loadProvidersLocked() {
    
    
    // create a passive location provider, which is always enabled
    PassiveProvider passiveProvider = new PassiveProvider(this);
    addProviderLocked(passiveProvider);
    mEnabledProviders.add(passiveProvider.getName());
    mPassiveProvider = passiveProvider;

    if (GnssLocationProvider.isSupported()) {
    
    
        // Create a gps location provider
        GnssLocationProvider gnssProvider = new GnssLocationProvider(mContext, this,
                mLocationHandler.getLooper());
        mGnssSystemInfoProvider = gnssProvider.getGnssSystemInfoProvider();
        mGnssBatchingProvider = gnssProvider.getGnssBatchingProvider();
        mGnssMetricsProvider = gnssProvider.getGnssMetricsProvider();
        mGnssStatusProvider = gnssProvider.getGnssStatusProvider();
        mNetInitiatedListener = gnssProvider.getNetInitiatedListener();
        addProviderLocked(gnssProvider);
        mRealProviders.put(LocationManager.GPS_PROVIDER, gnssProvider);
        mGnssMeasurementsProvider = gnssProvider.getGnssMeasurementsProvider();
        mGnssNavigationMessageProvider = gnssProvider.getGnssNavigationMessageProvider();
        mGpsGeofenceProxy = gnssProvider.getGpsGeofenceProxy();
    }

2.1, Framework calls the JNI layer method

GnssLocationProvider.java -> com_android_server_location_GnssLocationProvider.cpp

2.2, JNI layer calls Framework method

com_android_server_location_GnssLocationProvider.cpp -> GnssLocationProvider.java