Android GPS架构分析

/** Represents the standard
GPS interface. */
typedef struct {
/**
* Opens the interface and provides the
callback routines
* to the implemenation of this
interface.
*/
int
(*init)( GpsCallbacks* callbacks );
/** 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 location 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_DELETE_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 information. */
const void* (*get_extension)(const char*
name);
}
GpsInterface;

/** GPS callback structure.
*/
typedef struct {
gps_location_callback
location_cb;
gps_status_callback
status_cb;
gps_sv_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 information. */
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);

/** Represents a location.
*/
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 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;