AndroidGPS架构分析

1、以下摘自daniel wood的博客：android gps架构分析（gps启动过程图）gps启动过程图（基于google android 2.2代码）下面再贴一张从googlei/o大会文档里面截来的图android gps架构分析-previewandroid gps架构分析daniel wood 20101222转载时请注明出处和作者文章出处：作者：daniel wood-看android的gps模块有两个月了吧，终于可以写点东西出来。首先来看看gps模块的代码结构：framework：1.frameworks/base/location/java/android/location这里主

2、要是用来被app调用的，api包是android.location。2.frameworks/base/location/java/com/android/internal/location这个目录是framework对location服务的内部实现。3.frameworkservicesjavacomandroidserver这个目录只有一个文件|- locationmanagerservice.java是location服务对内部实现的一种封装。jni：frameworks/base/core/jni/android_location_gpslocationprovider.cppjni层

3、只有一个文件，起到承上启下的作用。上层承接framework，下层调用hal层具体硬件抽象实现。hal：hardware abstract layer 硬件抽象层hardwarelibhardware_legacygpshardwarelibhardware_legacyincludehardware_legacygps.hhal层相当于一个linux应用程序接口，通过open，close等操作，操作硬件设备。android的源代码只实现了模拟器的gps接口，具体在文件gps_qemu.c中。在2.2版本中提供了对qcom公司的gps的实现，在以下目录：hardwareqcom下面介绍几个重要

4、的数据结构：1. gpsinterface接口是gps模块中最重要的数据结构，它是底层驱动实现的接口，如果要porting到自己的板子上，就需要实现这些接口。该接口的定义在gps.h中，模拟器实现在gps_qemu.c中。/* represents the standard gps interface. */typedef struct /* opens the interface and provides the callback routines* to the implemenation of this interface.*/int (*init)( gpscallbacks* cal

5、lbacks );/* starts navigating. */int (*start)( void );/* stops navigating. */int (*stop)( void );/* closes the interface. */void (*cleanup)( void );/* injects the current time. */int (*inject_time)(gpsutctime time, int64_t timereference,int uncertainty);/* injects current location from another locat

6、ion provider* (typically cell id).* latitude and longitude are measured in degrees* expected accuracy is measured in meters*/int (*inject_location)(double latitude, double longitude, float accuracy);/* specifies that the next call to start will not use the* information defined in the flags. gps_dele

7、te_all is passed for* a cold start.*/void (*delete_aiding_data)(gpsaidingdata flags);/* fix_frequency represents the time between fixes in seconds.* set fix_frequency to zero for a single-shot fix.*/int (*set_position_mode)(gpspositionmode mode, int fix_frequency);/* get a pointer to extension infor

8、mation. */const void* (*get_extension)(const char* name); gpsinterface;2. gpscallbacks回调函数 这个是回调函数结构体，定义也在gps.h中。它们的实现是在android_location_gpslocationprovider.cpp中，google已经实现了，我们不需要做任何动作。/* gps callback structure. */typedef struct gps_location_callback location_cb;gps_status_callback status_cb;gps_sv_

9、status_callback sv_status_cb;gps_nmea_callback nmea_cb; gpscallbacks;/* callback with location information. */typedef void (* gps_location_callback)(gpslocation* location);/* callback with status information. */typedef void (* gps_status_callback)(gpsstatus* status);/* callback with sv status inform

10、ation. */typedef void (* gps_sv_status_callback)(gpssvstatus* sv_info);/* callback for reporting nmea sentences. */typedef void (* gps_nmea_callback)(gpsutctime timestamp, const char* nmea, int length);3. gpslocation表示locatin数据信息，底层驱动获得location的raw信息，通常是nmea码，然后通过解析就得到了location信息。/* represents a loc

11、ation. */typedef struct /* contains gpslocationflags bits. */uint16_t flags;/* represents latitude in degrees. */double latitude;/* represents longitude in degrees. */double longitude;/* represents altitude in meters above the wgs 84 reference* ellipsoid. */double altitude;/* represents speed in met

12、ers per second. */float speed;/* represents heading in degrees. */float bearing;/* represents expected accuracy in meters. */float accuracy;/* timestamp for the location fix. */gpsutctime timestamp; gpslocation;android gps架构分析（一）android gps架构分析daniel wood 20101222转载时请注明出处和作者文章出处：作者：daniel wood- 介绍完了

13、主体代码结构以及重要的数据结构后，下面来看看gps的定位服务（locationmanager）的启动过程。我总是喜欢追本溯源地从源头去认识事物。因为“人之初，性本善”，从事物的本性去认识事物。locationmanager 这项服务是在systemserver.java 中启动的，也就是系统启动之后，这个服务就已经启动了：systemserver.java frameworkbaseservicesjavacomandroidserver在systemserver.java的init2函数中启动了一个线程来注册android的诸多服务，如：bluetooth service，networkma

14、nagement service，notification manager等，当然也包括location service。systemserver.java frameworksbaseservicesjavacomandroidserverpublic static final void init2() slog.i(tag, entered the android system server!);thread thr = new serverthread();thr.setname(android.server.serverthread);thr.start();在serverthread

15、线程的run函数中locationmanager服务的代码段如下：2.1版本try log.i(tag, location manager);servicemanager.addservice(context.location_service, new locationmanagerservice(context); catch (throwable e) log.e(tag, failure starting location manager, e);2.2的代码中代码段如下形式：try slog.i(tag, location manager);location = new locatio

16、nmanagerservice(context);servicemanager.addservice(context.location_service, location); catch (throwable e) slog.e(tag, failure starting location manager 在run函数的后半部分，是服务对系统的反馈，就是systemready()函数。 locationmanager服务的反馈函数如下：if (locationf != null) locationf.systemready();其中的locationf 是locationmanagerserv

17、ice的final类型，就是一旦赋值，不能更改。final locationmanagerservice locationf = location;哇！locationmanager这项服务的反馈机制只在2.2的代码里面才有啊。2.1中的反馈机制中并没有locationmanager（当然有其他的服务反馈）。而在2.1版本中locationmanagerservice的构造函数如下：locationmanagerservice.java frameworksbaseservicesjavacomandroidserverpublic locationmanagerservice(context

18、 context) super();mcontext = context;thread thread = new thread(null, this, locationmanagerservice);thread.start();if (local_logv) log.v(tag, constructed locationmanager service);2.2版本 public locationmanagerservice(context context) super();mcontext = context;if (local_logv) slog.v(tag, constructed l

19、ocationmanager service);2.1是在构造函数的时候就启动一个自身服务线程。见构造函数。2.2是在反馈机制中通过systemready函数启动自身服务线程。如下：void systemready() / we defer starting up the service until the system is readythread thread = new thread(null, this, locationmanagerservice);thread.start();通过线程run函数，调用initialize函数:public void run()process.se

20、tthreadpriority(process.thread_priority_background);looper.prepare();mlocationhandler = new locationworkerhandler();initialize();looper.loop();发表于： 2010-12-22，修改于： 2010-12-24 09:37， android gps架构分析（二）android gps架构分析daniel wood 20101222转载时请注明出处和作者文章出处：作者：daniel wood-initialize函数locationmanagerservice

21、.javaframeworksbaseservicesjavacomandroidserverprivate void initialize() / create a wake lock, needs to be done before calling loadproviders() belowpowermanager powermanager = (powermanager) mcontext.getsystemservice(context.power_service);mwakelock = powermanager.newwakelock(powermanager.partial_wa

22、ke_lock, wakelock_key);/ load providersloadproviders(); .initialize函数中最重要的就是loadproviders函数了，该函数调用loadproviderslocked，然后loadproviderslocked函数又调用_loadproviderslocked函数。为什么要这么折腾呢?先来看一部分的_loadproviderslocked函数：private void _loadproviderslocked() / attempt to load real providers firstif (gpslocationprov

23、ider.issupported() / create a gps location providergpslocationprovider gpsprovider = new gpslocationprovider(mcontext, this);mgpsstatusprovider = gpsprovider.getgpsstatusprovider();mnetinitiatedlistener = gpsprovider.getnetinitiatedlistener();addprovider(gpsprovider);mgpslocationprovider = gpsprovid

24、er; .注意这个if语句，狠重要，因为在这个语句中得到了hal层的gps接口gpsinterface。就是通过调用gpslocationprovider的issupported()函数才调用到gps.cpphardware/libhardware_legacy/gps中的gps_get_interface()。这个issupported函数才是第一个吃螃蟹的人。（而不是jni层的init函数，这个下面会提到)。gpslocationprovider.cpp frameworksbaselocationjavacomandroidinternallocationpublic static bo

25、olean issupported() return native_is_supported();然而issupported只有一句话，果然是高手，一击必中。然后就调用native方法，也就是jni层定义的方法。native_is_supported函数对于jni层是android_location_gpslocationprovider_is_supported方法。android_location_gpslocationprovider.cpp frameworksbasecorejnistatic jboolean android_location_gpslocationprovider

26、_is_supported(jnienv* env, jclass clazz) if (!sgpsinterface)sgpsinterface = gps_get_interface();return (sgpsinterface != null);前面已经提到jni起到承上启下的作用，gps_get_interface函数属于hal层的调用，在文件gps.cpp中。gps.cpp hardwarelibhardware_legacygpsconst gpsinterface*gps_get_interface()if (sgpsinterface = null)gps_find_hard

27、ware();return sgpsinterface;然后通过gps_find_hardware函数去得到gps接口，下面只模拟器中的gpsinterface。static voidgps_find_hardware( void )#ifdef have_qemu_gps_hardwareif (qemu_check() sgpsinterface = gps_get_qemu_interface();if (sgpsinterface) logd(using qemu gps hardware emulationn);return;#endif#ifdef have_gps_hardwar

28、esgpsinterface = gps_get_hardware_interface();#endifif (!sgpsinterface)logd(no gps hardware on this devicen);gps_qemu.c hardwarelibhardware_legacygpsconst gpsinterface* gps_get_qemu_interface()return &qemugpsinterface;qemugpsinterface的整体实现就在文件gps_qemu.c中。static const gpsinterface qemugpsinterface =

29、qemu_gps_init,qemu_gps_start,qemu_gps_stop,qemu_gps_cleanup,qemu_gps_inject_time,qemu_gps_inject_location,qemu_gps_delete_aiding_data,qemu_gps_set_position_mode,qemu_gps_get_extension,;发表于： 2010-12-22，修改于： 2010-12-24 10:42，已浏览574次，android gps架构分析（三）android gps架构分析daniel wood 20101222转载时请注明出处和作者文章出处：

30、作者：daniel wood-在底层得到gps的接口之后， if (gpslocationprovider.issupported()（在文件locationmanagerservice.java中调用）语句得到true，然后进行下一步操作，在这里new了一个gpslocationprovider对象。代码如下：gpslocationprovider gpsprovider = new gpslocationprovider(mcontext, this);注意gpslocationprovider构造函数里面的两个参数：mcontext, this。下面来看看gpslocationprovi

31、der的构造函数的前面几句：public gpslocationprovider(context context, ilocationmanager locationmanager) mcontext = context;mlocationmanager = locationmanager;mnihandler = new gpsnetinitiatedhandler(context, this); . 在gpslocationprovider类里面的成员变量mlocationmanager是构造函数的第二个参数，就是说是locationmanagerservice对象。这一点在这里先明确。接

32、着看_loadproviderslocked函数。private void _loadproviderslocked() / attempt to load real providers firstif (gpslocationprovider.issupported() / create a gps location providergpslocationprovider gpsprovider = new gpslocationprovider(mcontext, this);mgpsstatusprovider = gpsprovider.getgpsstatusprovider();m

33、netinitiatedlistener = gpsprovider.getnetinitiatedlistener();addprovider(gpsprovider);mgpslocationprovider = gpsprovider;/ create a passive location provider, which is always enabledpassiveprovider passiveprovider = new passiveprovider(this);addprovider(passiveprovider);menabledproviders.add(passive

34、provider.getname();/ initialize external network location and geocoder servicesresources resources = mcontext.getresources();string servicename = resources.getstring(ernal.r.string.config_networklocationprovider);if (servicename != null) mnetworklocationprovider =new locationproviderp

35、roxy(mcontext, locationmanager.network_provider,servicename, mlocationhandler);addprovider(mnetworklocationprovider);servicename = resources.getstring(ernal.r.string.config_geocodeprovider);if (servicename != null) mgeocodeprovider = new geocoderproxy(mcontext, servicename);updateprov

36、iderslocked();在构造完gpslocationprovider之后将其add到全局变量arraylist mproviders中，备以后调用。在2.2中采取了一种passiveprovider的类，而在2.1中是通过locationproviderproxy代理类的方式。2.1中locationproviderproxy作为gpslocationprovider的代理作用在locationmanagerservice中，而2.2中的passiveprovider感觉这个类是个空壳。有待研究。然后启动了nerwork location和geocoder 两个service。但是可惜的

37、是这两个服务都无法启动，因为他们是通过配置文件conifg.xml frameworkbasecoreresresvalues得到服务的名字，然后启动服务的。但是在这个配置文件中，两个服务的名字都是null。conifg.xml frameworkbasecoreresresvaluesnullnull其实这也导致了，在调用getfromlocationname和getfromlocation两个函数时提示“service not available”，这个google android 2.2的bug。_loadproviderslocked函数的最后一句是调用updateprovidersl

38、ocked函数，仍然在locationmanagerservic.java文件中。locationmanagerservic.javaprivate void updateproviderslocked() for (int i = mproviders.size() - 1; i = 0; i-) locationproviderinterface p = mproviders.get(i);boolean isenabled = p.isenabled();string name = p.getname();boolean shouldbeenabled = isallowedbysett

39、ingslocked(name);if (isenabled & !shouldbeenabled) updateproviderlistenerslocked(name, false); else if (!isenabled & shouldbeenabled) updateproviderlistenerslocked(name, true); 从上面_loadproviderslocked函数的代码来看，在mproviders这个arraylist 中有两个元素（这一点未求证），一个是gpsprovider，另一个是passiveprovider。gpsprovider是 gpsloc

40、ationprovider类型的，它的isenabled函数返回的是false，因为它并没有被enable。而 passiveprovider是passiveprovider类型，它总是enable的。所以gpsprovider会调用else语句中的updateproviderlistenerslocked(name, true)函数。我们主要分析这个else语句，对于passiveprovider不做分析。private void updateproviderlistenerslocked(string provider, boolean enabled) int listeners = 0

41、;locationproviderinterface p = mprovidersbyname.get(provider);if (p = null) return;arraylist deadreceivers = null;arraylist records = mrecordsbyprovider.get(provider);if (records != null) final int n = records.size();for (int i=0; in; i+) updaterecord record = records.get(i);/ sends a notification m

42、essage to the receiverif (!record.mreceiver.callproviderenabledlocked(provider, enabled) if (deadreceivers = null) deadreceivers = new arraylist();deadreceivers.add(record.mreceiver);listeners+;if (deadreceivers != null) for (int i=deadreceivers.size()-1; i=0; i-) removeupdateslocked(deadreceivers.g

43、et(i);if (enabled) /enabled的值是truep.enable();if (listeners 0) p.setmintime(getmintimelocked(provider);p.enablelocationtracking(true); else p.enablelocationtracking(false);p.disable();我们只关注主体部分代码，就是在if(enabled)这个语句段里面，启动了gps的服务，具体将在下一篇进行分析。 发表于： 2010-12-24，修改于： 2010-12-24 13:29，已浏览852次，有评论5条android g

44、ps架构分析（四）android gps架构分析daniel wood 20101224转载时请注明出处和作者文章出处：作者：daniel wood-通过调用gpslocationprovider类的enable和enablelocationtracking函数就把gps的locationmanager服务启动起来了。下面对这两个函数进行分析。首先是enable函数。gpslocationprovider.javapublic void enable() synchronized (mhandler) mhandler.removemessages(enable);message m = me

45、ssage.obtain(mhandler, enable);m.arg1 = 1;mhandler.sendmessage(m);对了，这个要提一点，在2.2中加入了一个providerhandler类（extends handler），这个在2.1中是没有的，其实是换汤不换药的，对于函数调用的过程来说没有本质的改变。对于handler的机制我还没有研究过。public void handlemessage(message msg)switch (msg.what) case enable:if (msg.arg1 = 1) handleenable(); else handledisabl

46、e();break;case enable_tracking:handleenablelocationtracking(msg.arg1 = 1);break;.在handlemessage函数中，定义了各种message对应的处理函数。对于enable消息还带有一个参数，enable函数里面带的参数值为1，所以调用handleenable函数。private void handleenable() if (debug) log.d(tag, handleenable);if (menabled) return;menabled = native_init();if (menabled) if (msuplserverhost != null) native_set_agps_server(agps_type_s