GPS NMEA-0183标准数据介绍
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https://www.cnblogs.com/rechen/p/5135409.html (可以准确判断是否在定位)
源码分析：
https://www.ibm.com/developerworks/cn/opensource/os-cn-android-location/
1. 源码所在的目录
2.
http://ju.outofmemory.cn/entry/111182
3.
4. LocationManager生成实例的位置
5. frameworks/base/core/java/android/app/ContextImpl.java
registerService(LOCATION_SERVICE, new ServiceFetcher() {
public Object createService(ContextImpl ctx) {
IBinder b = ServiceManager.getService(LOCATION_SERVICE);
return new LocationManager(ctx, ILocationManager.Stub.asInterface(b));
}
});
而ServiceManager里的的"LOCATION_SERVICE"又是从com.android.server.SystemServer这个类添加进去的
if (!disableLocation) {
traceBeginAndSlog("StartLocationManagerService");
try {
location = new LocationManagerService(context);
ServiceManager.addService(Context.LOCATION_SERVICE, location);
} catch (Throwable e) {
reportWtf("starting Location Manager", e);
}
Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
traceBeginAndSlog("StartCountryDetectorService");
try {
countryDetector = new CountryDetectorService(context);
ServiceManager.addService(Context.COUNTRY_DETECTOR, countryDetector);
} catch (Throwable e) {
reportWtf("starting Country Detector", e);
}
Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
}
LocationManagerService的reportLocation方法触发了应用上层onLocationFound的回调
@Override
public void reportLocation(Location location, boolean passive) {
checkCallerIsProvider();
if (!location.isComplete()) {
Log.w(TAG, "Dropping incomplete location: " + location);
return;
}
mLocationHandler.removeMessages(MSG_LOCATION_CHANGED, location);
Message m = Message.obtain(mLocationHandler, MSG_LOCATION_CHANGED, location);
m.arg1 = (passive ? 1 : 0);
mLocationHandler.sendMessageAtFrontOfQueue(m);
}
顺藤摸瓜，最终找到
public boolean callLocationChangedLocked(Location location) {
if (mListener != null) {
try {
synchronized (this) {
// synchronize to ensure incrementPendingBroadcastsLocked()
// is called before decrementPendingBroadcasts()
mListener.onLocationChanged(new Location(location));
// call this after broadcasting so we do not increment
// if we throw an exeption.
incrementPendingBroadcastsLocked();
}
} catch (RemoteException e) {
return false;
}
} else {
那么LocationManagerService的reportLocation方法又是怎么被触发的呢？
1. ILocationManager.aidl
2. frameworks/base/location/java/android/location/ILocationManager.aidl
3.
4.
GPS定位漂移产生的原因：https://baike.1688.com/doc/view-d41865087.html
GPS的NEMA协议解析：https://blog.csdn.net/adazone/article/details/45152291
点到直线的距离计算公式：https://blog.csdn.net/bagboy_taobao_com/article/details/6291462
经纬度求坐标方位角： https://blog.csdn.net/u010175314/article/details/76093934
NMEA编码：https://baike.baidu.com/item/NMEA/9812575?fr=aladdin