Android GPS架构分析(五)
2011-06-03 17:00
501 查看
言归正传,分析sGpsInterface->init方法。
gps_qume.c
在sGpsInterface->init中,也就是在qemu_gps_init方法,首先调用了gps_state_init,其次注册了回调函数,再说一次,这个回调函数就是在JNI层实现的,而且有JNI层传下来的函数。
在这个gps_state_init函数中,首先打开串口,然后建立socket通信,然后建立线程监听底层数据上报,分别对应于代码中黄低部分。
3)建立线程监听事件
来看看GpsEventThread的run函数。
run函数中还是需要调用native函数:JNI:android_location_GpsLocationProvider_wait_for_event函数。这个函数就是在一个while循环里面等待事件的触发(由回调函数触发),然后调用GpsLocationProvider类的数据上报函数(Location数据)。这个在后面还会讲到。
分析完了enable函数以后就轮到enableLocationTracking函数了。
GpsLocationProvider.java
同样地,也采取Handler的方式。调用的是handleEnableLocationTracking函数。
调用startNavigating函数。
在startNavigating函数中,最有作用的语句就是调用native方法native_start。调用到了JNI层的android_location_GpsLocationProvider_start函数。
android_location_GpsLocationProvider.cpp
gps_qume.c
static int qemu_gps_init(GpsCallbacks* callbacks) { GpsState* s = _gps_state; if (!s->init) gps_state_init(s); if (s->fd < 0) return -1; s->callbacks = *callbacks; return 0; } |
static void gps_state_init( GpsState* state ) { state->init = 1; state->control[0] = -1; state->control[1] = -1; state->fd = -1; state->fd = qemu_channel_open( &state->channel, QEMU_CHANNEL_NAME, O_RDONLY ); if (state->fd < 0) { D("no gps emulation detected"); return; } D("gps emulation will read from '%s' qemud channel", QEMU_CHANNEL_NAME ); if ( socketpair( AF_LOCAL, SOCK_STREAM, 0, state->control ) < 0 ) { LOGE("could not create thread control socket pair: %s", strerror(errno)); goto Fail; } if ( pthread_create( &state->thread, NULL, gps_state_thread, state ) != 0 ) { LOGE("could not create gps thread: %s", strerror(errno)); goto Fail; } D("gps state initialized"); return; Fail: gps_state_done( state ); } |
3)建立线程监听事件
mEventThread = new GpsEventThread(); mEventThread.start(); |
public void run() { if (DEBUG) Log.d(TAG, "GpsEventThread starting"); // Exit as soon as disable() is called instead of waiting for the GPS to stop. while (mEnabled) { // this will wait for an event from the GPS, // which will be reported via reportLocation or reportStatus native_wait_for_event(); } if (DEBUG) Log.d(TAG, "GpsEventThread exiting"); } } |
static void android_location_GpsLocationProvider_wait_for_event(JNIEnv* env, jobject obj) { pthread_mutex_lock(&sEventMutex); while (sPendingCallbacks == 0) { pthread_cond_wait(&sEventCond, &sEventMutex); } ... } |
GpsLocationProvider.java
public void enableLocationTracking(boolean enable) { synchronized (mHandler) { mHandler.removeMessages(ENABLE_TRACKING); Message m = Message.obtain(mHandler, ENABLE_TRACKING); m.arg1 = (enable ? 1 : 0); mHandler.sendMessage(m); } } |
private void handleEnableLocationTracking(boolean enable) { if (enable) { mTTFF = 0; mLastFixTime = 0; startNavigating(); } else { mAlarmManager.cancel(mWakeupIntent); mAlarmManager.cancel(mTimeoutIntent); stopNavigating(); } } |
private void startNavigating() { if (!mStarted) { if (DEBUG) Log.d(TAG, "startNavigating"); mStarted = true; int positionMode; if (Settings.Secure.getInt(mContext.getContentResolver(), Settings.Secure.ASSISTED_GPS_ENABLED, 1) != 0) { positionMode = GPS_POSITION_MODE_MS_BASED; } else { positionMode = GPS_POSITION_MODE_STANDALONE; } if (!native_start(positionMode, false, 1)) { mStarted = false; Log.e(TAG, "native_start failed in startNavigating()"); return; } ... |
android_location_GpsLocationProvider.cpp
相关文章推荐
- Android GPS架构分析<二>
- Android GPS架构分析(一)
- Android GPS架构分析(gps启动过程图)
- Android GPS架构分析(gps启动过程图)
- Android GPS架构分析(二)
- Android GPS架构分析(一)
- Android GPS架构分析(三)
- Android GPS架构分析
- Android GPS架构分析-preview
- Android GPS架构分析(四)
- Android GPS架构分析(五)
- Android GPS架构分析详解
- Android GPS架构分析(六)
- Android GPS架构分析(一)
- Android GPS架构分析(二)
- Android GPS架构分析(二)
- Android GPS架构分析(三)
- Android GPS架构分析(三)
- Android GPS架构分析-preview
- Android GPS架构分析(四)