GPS HAL層代碼在目錄trunk/Android/hardware/xxx/gps/skytraqskytraq_gsp.c，向下與硬件驅動通訊，向上提供接口
GPS JNI層層代碼在目錄trunk/Android/frameworks/base/services/jni/com_android_server_location_GpsLocationProvider.cpp C與java轉換，給java層提供接口
GPS framework層代碼目錄Android/frameworks/base/services/java/com/android/server下，主要文件是location服務對內部的封裝並提供provider服務
Android/frameworks/base/location/java/com/android/internal/location這個是framework對location服務內部的實現
啓動GPS服務代碼流程如下
public static void main(String[] args)
-->ServerThread thr = new ServerThread();
-->location = new LocationManagerService(context);
-->ServiceManager.addService(Context.LOCATION_SERVICE, location);
-->locationF.systemRunning()
-->systemRunning()
-->loadProvidersLocked();
-->GpsLocationProvider gpsProvider = new GpsLocationProvider(mContext, this, mLocationHandler.getLooper());
-->class_init_native();
-->android_location_GpsLocationProvider_class_init_native(JNIEnv* env, jclass clazz)
-->err = module->methods->open(module, GPS_HARDWARE_MODULE_ID, &device);
-->pen_gps(const struct hw_module_t *module, char const *name, struct hw_device_t **device)
-->sGpsInterface = gps_device->get_gps_interface(gps_device);
-->const GpsInterface *gps__get_gps_interface(struct gps_device_t *dev)
-->return &skytraqGpsInterface;
-->GpsLocationProvider.isSupported()
-->native_is_supported()
-->android_location_GpsLocationProvider_is_supported(JNIEnv* env, jclass clazz)
-->return (sGpsInterface != NULL);
-->updateProvidersLocked
--> updateProviderListenersLocked
--> applyRequirementsLocked(provider);
--> p.setRequest(providerRequest, worksource);
--> public void setRequest(ProviderRequest request, WorkSource source)
--> sendMessage(SET_REQUEST, 0, new GpsRequest(request, source));
-->public void handleMessage(Message msg)
-->handleSetRequest(gpsRequest.request, gpsRequest.source);
-->startNavigating(singleShot);
-->native_set_position_mode(mPositionMode, GPS_POSITION_RECURRENCE_PERIODIC,interval, 0, 0)
-->native_start()
Android系統運行的第一個進程就是init進程，在該進程中創建的第一個虛擬機就是zygote，zygote孵化的第一個虛擬機就是Dalvik,該進程就是SystemServer,
對於的SystemServer代碼是framework\base\services\java\com\android\server\SystemServer.java
該SystemServer對於的第一個運行函數就是main
public static void main(String[] args) //SystemServer運行的第一個函數
ServerThread thr = new ServerThread(); //初始化一個server線程
class ServerThread
{
public void initAndLoop()
{
if (!disableLocation) //開始的時候這裏的 disableLocation = false
{
try{
Slog.i(TAG, "Location Manager");
<1> location = new LocationManagerService(context); //實例化一個LocationManagerService服務，該服務主要用來管理GPS地理位置的變化
ServiceManager.addService(Context.LOCATION_SERVICE, location); //將這個service添加到SystemManager中
}
catch (Throwable e)
{
reportWtf("starting Location Manager", e);
}
try {
Slog.i(TAG, "Country Detector");
countryDetector = new CountryDetectorService(context);//實例化一個CountryDetectorService服務，用來探測不同國家，也就是不同地區和時區
ServiceManager.addService(Context.COUNTRY_DETECTOR, countryDetector);
} catch (Throwable e) {
reportWtf("starting Country Detector", e);
}
}
ActivityManagerService.self().systemReady(new Runnable()
{
public void run()
{
try
{
<2> if (locationF != null) locationF.systemRunning();//在<1>的位置已給locationF賦值，在這裏調用LocationManagerService的systemRunning()函數
}
catch(Throwable e)
{
reportWtf("Notifying Location Service running", e);
}
}
}
}
}
接下來分析LocationManagerService(context)
/**framework\base\services\java\com\android\server\LocationManagerService.java**/
public class LocationManagerService extends ILocationManager.Stub
{
public void systemRunning() //該函數有<2>處調用
{
synchronized (mLock)
{
/*GPS啓動到運行及監聽都在這兩個函數裏*/
<3> loadProvidersLocked(); //在這裏加載各種provider
<4> updateProvidersLocked(); //加載後更新
}
}
}
/**framework\base\services\java\com\android\server\LocationManagerService.java**/
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;
// Create a gps location provider
<5> GpsLocationProvider gpsProvider = new GpsLocationProvider(mContext, this,
mLocationHandler.getLooper());
<6> if (GpsLocationProvider.isSupported()) //這裏調用JNI的函數接口
{
mGpsStatusProvider = gpsProvider.getGpsStatusProvider(); //獲取gps狀態provider
mNetInitiatedListener = gpsProvider.getNetInitiatedListener(); //初始網絡監聽
addProviderLocked(gpsProvider); //將gpsProvider添加到mProviders中
mRealProviders.put(LocationManager.GPS_PROVIDER, gpsProvider);
}
}
/**分析 <5> ***/
public class GpsLocationProvider implements LocationProviderInterface
{
static { class_init_native(); } //在這裏調用JNI的android_location_GpsLocationProvider_class_init_native函數
}
static void android_location_GpsLocationProvider_class_init_native(JNIEnv* env, jclass clazz)
{
err = module->methods->open(module, GPS_HARDWARE_MODULE_ID, &device);//打開GPS設備文件，對應trunk/Android/hardware/xxx/gps/skytraq/skytraq_gps.c
-->static int open_gps(const struct hw_module_t *module, char const *name, struct hw_device_t **device)
//獲取gpsInterface接口，該函數接口在trunk/Android/hardware/xxx/gps/skytraq/skytraq_gps.c中,對應的函數是gps__get_gps_interface
sGpsInterface = gps_device->get_gps_interface(gps_device);
}
const GpsInterface *gps__get_gps_interface(struct gps_device_t *dev)
{
return &skytraqGpsInterface;
}
/**分析 <6> **/
public static boolean GpsLocationProvider.isSupported()
{
return native_is_supported(); //該函數對應JNI的函數如下
}
static jboolean android_location_GpsLocationProvider_is_supported(JNIEnv* env, jclass clazz)
{
return (sGpsInterface != NULL);
}
GpsLocationProvider.isSupported()返回true，所以會走if{}裏面的。在網上查閱資料，都是基於2.3的系統，2.3的系統裏是直接在isSupported()函數裏來獲取接口，沒有在GpsLocationProvider類中實現調用class_init_native()來獲取接口
/**分析 <4> **/
/**framework\base\services\java\com\android\server\LocationManagerService.java**/
private void updateProvidersLocked()
{
for (int i = mProviders.size() - 1; i >= 0; i--)
{
boolean isEnabled = p.isEnabled(); //開始的時候返回false
boolean shouldBeEnabled = isAllowedByCurrentUserSettingsLocked(name); //在loadProvidersLocked()函數就說了，一直是enabled
所以會走else
else if (!isEnabled && shouldBeEnabled)
{
<7> updateProviderListenersLocked(name, true, mCurrentUserId);
changesMade = true;
}
}
/*發送廣播，app和framework都可以接受該廣播*/
if (changesMade) {
mContext.sendBroadcastAsUser(new Intent(LocationManager.PROVIDERS_CHANGED_ACTION),
UserHandle.ALL);
mContext.sendBroadcastAsUser(new Intent(LocationManager.MODE_CHANGED_ACTION),
UserHandle.ALL);
}
}
/**分析 <7> framework\base\services\java\com\android\server\locationManagerService.java **/
private void updateProviderListenersLocked(String provider, boolean enabled, int userId)
{
if (records != null)
{
//這裏主要是從UserHandle裏解析UserId 是否等於 mCurrentUserId，如果是則發送notification給receiver
}
if (enabled) //這裏的 enabled == true
{
<8> p.enable();
if (listeners > 0)
{
<9> applyRequirementsLocked(provider);
}
}
else
{
p.disable();
}
}
/**分析 <8> framework\base\services\java\com\android\server\location\gpsLocationProvider.java**/
public void enable()
{
synchronized (mLock)
{
if (mEnabled) return;//開始的時候這裏是false
mEnabled = true;
}
<10> sendMessage(ENABLE, 1, null);//發送消息
}
/**分析 <10> base\services\java\com\android\server\location\gpsLocationProvider.java**/
private void sendMessage(int message, int arg, Object obj)
{
// hold a wake lock until this message is delivered
// note that this assumes the message will not be removed from the queue before
// it is handled (otherwise the wake lock would be leaked).
mWakeLock.acquire();
<11> mHandler.obtainMessage(message, arg, 1, obj).sendToTarget(); //通過handler機制來發送消息
}
/**分析 <11> base\services\java\com\android\server\location\gpsLocationProvider.java**/
private final class ProviderHandler extends Handler
{
public void handleMessage(Message msg)
{
switch (message)
{
case ENABLE: //有<10>可知，message == ENABLE ， msg.arg1 == 1
if (msg.arg1 == 1) {
<12> handleEnable(); //所以會調用這個函數
} else {
handleDisable();
}
break;
.....
}
}
}
/**分析 <12> framework\base\services\java\com\android\server\location\gpsLocationProvider.java**/
private void handleEnable()
{
<13> boolean enabled = native_init(); //調用JNI中的 static jboolean android_location_GpsLocationProvider_init(JNIEnv* env, jobject obj)
if (enabled)
{
mSupportsXtra = native_supports_xtra(); //native_supports_xtra()直接返回true，在class_init_native()已經賦值
if (mSuplServerHost != null)
{
/*這裏沒做任何事，因爲sAGpsInterface爲空，代碼流程如下*/
native_set_agps_server(AGPS_TYPE_SUPL, mSuplServerHost, mSuplServerPort);
-->static void android_location_GpsLocationProvider_set_agps_server(JNIEnv* env, jobject obj, jint type, jstring hostname, jint port)
-->if (!sAGpsInterface) return;
-->sAGpsInterface = (const AGpsInterface*)sGpsInterface->get_extension(AGPS_INTERFACE);
-->static const void *skytraq_gps_get_extension(const char* name)
{
ALOGD("%s: called", __FUNCTION__);
return NULL;
}
}
if (mC2KServerHost != null) { //同理這裏也直接返回了
native_set_agps_server(AGPS_TYPE_C2K, mC2KServerHost, mC2KServerPort);
}
}else{
synchronized (mLock) {
mEnabled = false;
}
Log.w(TAG, "Failed to enable location provider");
}
}
/**分析 <13> framework\base\services\jni\com_android_server_location_GpsLocationProvider.cpp **/
static jboolean android_location_GpsLocationProvider_init(JNIEnv* env, jobject obj)
{
<14> if (!sGpsInterface || sGpsInterface->init(&sGpsCallbacks) != 0)//sGpsInterface不爲null，在一開始的就已賦值，所以會調用init函數
return false;
.....
}
/**分析 <14> hardware\xxx\gps\skytraq\Skytraq_gps.c **/
static int skytraq_gps_init(GpsCallbacks* callbacks) //callbacks回調函數時有JNI傳下來的，在JNI中實現的
{
GpsState* s = &_gps_state; //該結構圖數組初始化的時候都爲0
if (!s->init)
<15> gps_state_init(s, callbacks);
}
/**分析 <15> hardware\xxx\gps\skytraq\Skytraq_gps.c **/
static void gps_state_init( GpsState* state, GpsCallbacks* callbacks )
{
state->fd = gps_channel_open(GPS_CHANNEL_NAME);
--> fd = open("/dev/skytraq_gps_ipc", O_RDWR | O_SYNC); //打開串口
int ret = ioctl(state->fd, GPS_IPC_SET, &gps_connect_info); //調用驅動函數ioctl設置gps
state->thread = callbacks->create_thread_cb( "gps_state_thread", gps_state_thread, state );//創建線程，用來監聽發送的命令和監聽數據上報，
}
/**分析<9> frwmework\base\services\java\com\android\server\LocationManagerService.java
private void applyRequirementsLocked(String provider)
{
//設置worksource和providerRequest
.....
<16> p.setRequest(providerRequest, worksource); //location provider 發送請求
}
/**分析<16> frwmework\base\services\java\com\android\server\location\GpsLocationProvider.java**/
public void setRequest(ProviderRequest request, WorkSource source)
{
<17> sendMessage(SET_REQUEST, 0, new GpsRequest(request, source)); //發送消息，SET_REQUEST == 3
}
/**分析<17> frwmework\base\services\java\com\android\server\location\GpsLocationProvider.java**/
public void handleMessage(Message msg)
{
...
case SET_REQUEST:
GpsRequest gpsRequest = (GpsRequest) msg.obj;
<18> handleSetRequest(gpsRequest.request, gpsRequest.source);
break;
}
/**分析<18> frwmework\base\services\java\com\android\server\location\GpsLocationProvider.java**/
private void handleSetRequest(ProviderRequest request, WorkSource source)
{
...
<19> startNavigating(singleShot);//開始導航
}
/**分析<19> frwmework\base\services\java\com\android\server\location\GpsLocationProvider.java**/
private void startNavigating(boolean singleShot)
{
<20> native_set_position_mode(mPositionMode, GPS_POSITION_RECURRENCE_PERIODIC, interval, 0, 0)//該函數在HAL層直接返回了，沒做任何事
<21> native_start()
}
/**分析<20> framework\base\services\jni\com_android_server_location_GpsLocationProvider.cpp**/
static jboolean android_location_GpsLocationProvider_set_position_mode(JNIEnv* env, jobject obj,
jint mode, jint recurrence, jint min_interval, jint preferred_accuracy, jint preferred_time)
{
if (sGpsInterface)
<22> return (sGpsInterface->set_position_mode(mode, recurrence, min_interval, preferred_accuracy,
preferred_time) == 0); //調用HAL層接口
}
/**分析<22> xxx\gps\skytraq\skytraq.gps.c**/
static int skytraq_gps_set_position_mode(GpsPositionMode mode,
GpsPositionRecurrence recurrence,
uint32_t min_interval,
uint32_t preferred_accuracy,
uint32_t preferred_time)
{
ALOGD("%s: called", __FUNCTION__);
return 0;
}
/**分析<21> framework\base\services\jni\com_android_server_location_GpsLocationProvider.cpp**/
static jboolean android_location_GpsLocationProvider_start(JNIEnv* env, jobject obj)
{
if (sGpsInterface)
<23> return (sGpsInterface->start() == 0); //調用HAL 層的static int skytraq_gps_start()
}
/**分析<23> xxx\gps\skytraq\skytraq.gps.c**/
static int skytraq_gps_start()
{
gps_state_start(s);
-->s->status = CMD_START;
/*在<15>線程函數gps_state_thread()中while(1)中等該命令，進入獲取數據*/
}
此時GPS就已運行
Android4.4 GPS框架分析
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