Android系统Gps分析.docx
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Android系统Gps分析
Android系统Gps分析
1.
2.GPS架构
3.GPS分析
1.头文件
2.硬件适配层
3.JNI适配层
4.JavaFramework
1.接口和类简介
2.使用Gps编程接口
3.接口和类分析
4.参考文章
1GPS架构
2GPS分析
2.1头文件
头文件定义在：
hardware/libhardware/include/hardware/gps.h，定义了GPS底层相关的结构体和接口
∙GpsLocation
GPS位置信息结构体，包含经纬度，高度，速度，方位角等。
/** Flags to indicate which values are valid in a GpsLocation. */
typedef uint16_t GpsLocationFlags;
// IMPORTANT:
Note that the following values must match
// constants in GpsLocationProvider.java.
/** GpsLocation has valid latitude and longitude. */
#define GPS_LOCATION_HAS_LAT_LONG 0x0001
/** GpsLocation has valid altitude. */
#define GPS_LOCATION_HAS_ALTITUDE 0x0002
/** GpsLocation has valid speed. */
#define GPS_LOCATION_HAS_SPEED 0x0004
/** GpsLocation has valid bearing. */
#define GPS_LOCATION_HAS_BEARING 0x0008
/** GpsLocation has valid accuracy. */
#define GPS_LOCATION_HAS_ACCURACY 0x0010
/** Represents a location. */
typedef struct {
/** set to sizeof（GpsLocation） */
size_t size;
/** 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 meters 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;
/**FlagstoindicatewhichvaluesarevalidinaGpsLocation.*/
typedefuint16_tGpsLocationFlags;
//IMPORTANT:
Notethatthefollowingvaluesmustmatch
//constantsinGpsLocationProvider.java.
/**GpsLocationhasvalidlatitudeandlongitude.*/
#defineGPS_LOCATION_HAS_LAT_LONG0x0001
/**GpsLocationhasvalidaltitude.*/
#defineGPS_LOCATION_HAS_ALTITUDE0x0002
/**GpsLocationhasvalidspeed.*/
#defineGPS_LOCATION_HAS_SPEED0x0004
/**GpsLocationhasvalidbearing.*/
#defineGPS_LOCATION_HAS_BEARING0x0008
/**GpsLocationhasvalidaccuracy.*/
#defineGPS_LOCATION_HAS_ACCURACY0x0010
/**Representsalocation.*/
typedefstruct{
/**settosizeof（GpsLocation）*/
size_tsize;
/**ContainsGpsLocationFlagsbits.*/
uint16_tflags;
/**Representslatitudeindegrees.*/
doublelatitude;
/**Representslongitudeindegrees.*/
doublelongitude;
/**RepresentsaltitudeinmetersabovetheWGS84reference
*ellipsoid.*/
doublealtitude;
/**Representsspeedinmeterspersecond.*/
floatspeed;
/**Representsheadingindegrees.*/
floatbearing;
/**Representsexpectedaccuracyinmeters.*/
floataccuracy;
/**Timestampforthelocationfix.*/
GpsUtcTimetimestamp;
}GpsLocation;
∙GpsStatus
GPS状态包括5种状态，分别为未知，正在定位，停止定位，启动未定义，未启动。
/** GPS status event values. */
typedef uint16_t GpsStatusValue;
// IMPORTANT:
Note that the following values must match
// constants in GpsLocationProvider.java.
/** GPS status unknown. */
#define GPS_STATUS_NONE 0
/** GPS has begun navigating. */
#define GPS_STATUS_SESSION_BEGIN 1
/** GPS has stopped navigating. */
#define GPS_STATUS_SESSION_END 2
/** GPS has powered on but is not navigating. */
#define GPS_STATUS_ENGINE_ON 3
/** GPS is powered off. */AgpsCallbacks
AgpsInterface
#define GPS_STATUS_ENGINE_OFF 4
/** Represents the status. */
typedef struct {
/** set to sizeof（GpsStatus） */
size_t size;
GpsStatusValue status;
} GpsStatus;
/**GPSstatuseventvalues.*/
typedefuint16_tGpsStatusValue;
//IMPORTANT:
Notethatthefollowingvaluesmustmatch
//constantsinGpsLocationProvider.java.
/**GPSstatusunknown.*/
#defineGPS_STATUS_NONE0
/**GPShasbegunnavigating.*/
#defineGPS_STATUS_SESSION_BEGIN1
/**GPShasstoppednavigating.*/
#defineGPS_STATUS_SESSION_END2
/**GPShaspoweredonbutisnotnavigating.*/
#defineGPS_STATUS_ENGINE_ON3
/**GPSispoweredoff.*/AgpsCallbacks
AgpsInterface
#defineGPS_STATUS_ENGINE_OFF4
/**Representsthestatus.*/
typedefstruct{
/**settosizeof（GpsStatus）*/
size_tsize;
GpsStatusValuestatus;
}GpsStatus;
∙GpsSvInfo
GPS卫星信息，包含卫星编号，信号强度，卫星仰望角，方位角等。
/** Represents SV information. */
typedef struct {
/** set to sizeof（GpsSvInfo） */
size_t size;
/** Pseudo-random number for the SV. */
int prn;
/** Signal to noise ratio. */
float snr;
/** Elevation of SV in degrees. */
float elevation;
/** Azimuth of SV in degrees. */
float azimuth;
} GpsSvInfo;
/**RepresentsSVinformation.*/
typedefstruct{
/**settosizeof（GpsSvInfo）*/
size_tsize;
/**Pseudo-randomnumberfortheSV.*/
intprn;
/**Signaltonoiseratio.*/
floatsnr;
/**ElevationofSVindegrees.*/
floatelevation;
/**AzimuthofSVindegrees.*/
floatazimuth;
}GpsSvInfo;
∙GpsSvStatus
GPS卫星状态，包含可见卫星数和信息，星历时间，年历时间等。
/** Represents SV status. */
typedef struct {
/** set to sizeof（GpsSvStatus） */
size_t size;
/** Number of SVs currently visible. */
int num_svs;
/** Contains an array of SV information. */
GpsSvInfo sv_list[GPS_MAX_SVS];
/** Represents a bit mask indicating which SVs
* have ephemeris data.
*/
uint32_t ephemeris_mask;
/** Represents a bit mask indicating which SVs
* have almanac data.
*/
uint32_t almanac_mask;
/**
* Represents a bit mask indicating which SVs
* were used for computing the most recent position fix.
*/
uint32_t used_in_fix_mask;
} GpsSvStatus;
/**RepresentsSVstatus.*/
typedefstruct{
/**settosizeof（GpsSvStatus）*/
size_tsize;
/**NumberofSVscurrentlyvisible.*/
intnum_svs;
/**ContainsanarrayofSVinformation.*/
GpsSvInfosv_list[GPS_MAX_SVS];
/**RepresentsabitmaskindicatingwhichSVs
*haveephemerisdata.
*/
uint32_tephemeris_mask;
/**RepresentsabitmaskindicatingwhichSVs
*havealmanacdata.
*/
uint32_talmanac_mask;
/**
*RepresentsabitmaskindicatingwhichSVs
*wereusedforcomputingthemostrecentpositionfix.
*/
uint32_tused_in_fix_mask;
}GpsSvStatus;
∙GpsCallbacks
回调函数定义
/** Callback with location information. 向上层传递GPS位置信息
* Can only be called from a thread created by create_thread_cb.
*/
typedef void （* gps_location_callback）（GpsLocation* location）;
/** Callback with status information. 向上层传递GPS状态信息
* Can only be called from a thread created by create_thread_cb.
*/
typedef void （* gps_status_callback）（GpsStatus* status）;
/** Callback with SV status information. 向上层传递GPS卫星信息
* Can only be called from a thread created by create_thread_cb.
*/
typedef void （* gps_sv_status_callback）（GpsSvStatus* sv_info）;
/** Callback for reporting NMEA sentences. 向上层传递MEMA数据
* Can only be called from a thread created by create_thread_cb.
*/
typedef void （* gps_nmea_callback）（GpsUtcTime timestamp, const char* nmea, int length）;
/** Callback to inform framework of the GPS engine's capabilities.告知GPS模块可以实现的功能
* Capability parameter is a bit field of GPS_CAPABILITY_* flags.
*/
typedef void （* gps_set_capabilities）（uint32_t capabilities）;
/** Callback utility for acquiring the GPS wakelock.上锁，防止处理GPS事件时中止。
* This can be used to prevent the CPU from suspending while handling GPS events.
*/
typedef void （* gps_acquire_wakelock）（）;
/** Callback utility for releasing the GPS wakelock. */释放锁
typedef void （* gps_release_wakelock）（）;
/** Callback for creating a thread that can call into the Java framework code.等待上层请求
* This must be used to create any threads that report events up to the framework.
*/
typedef pthread_t （* gps_create_thread）（const char* name, void （*start）（void *）, void* arg）;
/** GPS callback structure. */
typedef struct {
/** set to sizeof（GpsCallbacks） */
size_t size;
gps_location_callback location_cb;
gps_status_callback status_cb;
gps_sv_status_callback sv_status_cb;
gps_nmea_callback nmea_cb;
gps_set_capabilities set_capabilities_cb;
gps_acquire_wakelock acquire_wakelock_cb;
gps_release_wakelock release_wakelock_cb;
gps_create_thread create_thread_cb;
} GpsCallbacks;
/**Callbackwithlocationinformation.向上层传递GPS位置信息
*Canonlybecalledfromathreadcreatedbycreate_thread_cb.
*/
typedefvoid（*gps_location_callback）（GpsLocation*location）;
/**Callbackwithstatusinformation.向上层传递GPS状态信息
*Canonlybecalledfromathreadcreatedbycreate_thread_cb.
*/
typedefvoid（*gps_status_callback）（GpsStatus*status）;
/**CallbackwithSVstatusinformation.向上层传递GPS卫星信息
*Canonlybecalledfromathreadcreatedbycreate_thread_cb.
*/
typedefvoid（*gps_sv_status_callback）（GpsSvStatus*sv_info）;
/**CallbackforreportingNMEAsentences.向上层传递MEMA数据
*Canonlybecalledfromathreadcreatedbycreate_thread_cb.
*/
typedefvoid（*gps_nmea_callback）（GpsUtcTimetimestamp,constchar*nmea,intlength）;
/**CallbacktoinformframeworkoftheGPSengine'scapabilities.告知GPS模块可以实现的功能
*CapabilityparameterisabitfieldofGPS_CAPABILITY_*flags.
*/
typedefvoid（*gps_set_capabilities）（uint32_tcapabilities）;
/**CallbackutilityforacquiringtheGPSwakelock.上锁，防止处理GPS事件时中止。
*ThiscanbeusedtopreventtheCPUfromsuspendingw
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