GPS定位研究之gps位置改变监听源码分析（Android10）
一、安卓中GPS定位更新监控
在安卓很多提供定位服务的App应用程序中，不仅需要获取当前的位置信息，还需要监视位置的变化，在位置改变时获取到当前的位置信息。gps定位中LocationManager提供了一种便捷、高效的位置监视方法requestLocationUpdates(String provider, long minTime, float minDistance,LocationListener listener)，可以根据位置的距离变化和时间间隔设定，产生位置改变事件的条件，这样可以避免因微小的距离变化而产生大量的位置改变事件 ，LocationManager中设定监听位置变化的参考代码如下:
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
以下将分析LocationManager中requestLocationUpdates到LocationManagerService中requestLocationUpdates的流程来分析GPS定位中的交互。
二、requestLocationUpdates调用流程追踪
2.1 LocationManager中requestLocationUpdates调用分析
LocationManager源码文件位于:
frameworks\base\location\java\android\location\LocationManager.java
LocationManager中对外提供了很多API接口供App调用来实现gps定位。其中位置改变监控的接口的实现代码如下:
//从代码中可以看到调用了 requestLocationUpdates(LocationRequest request, LocationListener listener,Looper looper, PendingIntent intent)
@RequiresPermission(anyOf = {ACCESS_COARSE_LOCATION, ACCESS_FINE_LOCATION})
public void requestLocationUpdates(@NonNull String provider, long minTime, float minDistance,
@NonNull LocationListener listener) {
checkProvider(provider);
checkListener(listener);
LocationRequest request = LocationRequest.createFromDeprecatedProvider(
provider, minTime, minDistance, false);
requestLocationUpdates(request, listener, null, null);
}
// 该方法最终调用了mService.requestLocationUpdates和LocationManagerService进行binder通信。
//所以requestLocationUpdates的真正实现存在于LocationManagerService
@UnsupportedAppUsage
private void requestLocationUpdates(LocationRequest request, LocationListener listener,
Looper looper, PendingIntent intent) {
String packageName = mContext.getPackageName();
// wrap the listener class
ListenerTransport transport = wrapListener(listener, looper);
try {
mService.requestLocationUpdates(request, transport, intent, packageName);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
在LocationManager中mService定义如下:
private final ILocationManager mService;
从定义可以看出类型为ILocationManager。在源码中没有搜索到ILocationManager.java类,存在ILocationManager.aidl，aidl文件在源码编译期间会生成对应java文件。源码中aidl具体的java代码如何查看可以参考:。
2.2 LocationManagerService中requestLocationUpdates调用分析
LocationManagerService源码文件位于:
frameworks\base\services\core\java\com\android\server\LocationManagerService.java
该文件中requestLocationUpdates方法的 关键实现如下:
@Override
public void requestLocationUpdates(LocationRequest request, ILocationListener listener,PendingIntent intent, String packageName) {
//...省略
Receiver receiver;
if (intent != null) {
receiver = getReceiverLocked(intent, pid, uid, packageName, workSource,
hideFromAppOps);
} else {
//LocationManager调用requestLocationUpdates的时候，intent=null。所以会执行如下的代码分支,getReceiverLocked会创建一个Receiver对象来管理app注册的监听。
receiver = getReceiverLocked(listener, pid, uid, packageName, workSource,
hideFromAppOps);
}
//该方法更新receiver的一些参数，方便后续收到位置更新之后进行遍历调用
requestLocationUpdatesLocked(sanitizedRequest, receiver, uid, packageName);
//...省略
}
}
@GuardedBy("mLock")
private void requestLocationUpdatesLocked(LocationRequest request, Receiver receiver,
int uid, String packageName) {
//...省略
UpdateRecord record = new UpdateRecord(name, request, receiver);
if (D) {
Log.d(TAG, "request " + Integer.toHexString(System.identityHashCode(receiver))
+ " " + name + " " + request + " from " + packageName + "(" + uid + " "
+ (record.mIsForegroundUid ? "foreground" : "background")
+ (isThrottlingExemptLocked(receiver.mCallerIdentity)
? " [whitelisted]" : "") + ")");
}
UpdateRecord oldRecord = receiver.mUpdateRecords.put(name, record);
if (oldRecord != null) {
oldRecord.disposeLocked(false);
}
if (!provider.isUseableLocked() && !isSettingsExemptLocked(record)) {
// Notify the listener that updates are currently disabled - but only if the request
// does not ignore location settings
receiver.callProviderEnabledLocked(name, false);
}
receiver.updateMonitoring(true);
}
//getReceiverLocked方法会缓存LocationManager传过来的位置监听器，后续有位置改变就会遍历mReceivers中的缓存对象，然后通知通知位置改变
@GuardedBy("mLock")
private Receiver getReceiverLocked(ILocationListener listener, int pid, int uid,String packageName, WorkSource workSource, boolean hideFromAppOps) {
IBinder binder = listener.asBinder();
Receiver receiver = mReceivers.get(binder);
if (receiver == null) {
//创建接收对象
receiver = new Receiver(listener, null, pid, uid, packageName, workSource,
hideFromAppOps);
if (!linkToListenerDeathNotificationLocked(receiver.getListener().asBinder(),
receiver)) {
return null;
}
//缓存接收对象
mReceivers.put(binder, receiver);
}
return receiver;
}
在以上分析中，位置监听api调用之后追踪会创建Receiver对象进行包装。Receiver类定义在LocationManagerService.java中，以下是该类中和位置变化监听相关的部分代码:
private final class Receiver extends LinkedListenerBase implements PendingIntent.OnFinished {
//...省略
//缓存位置改变的监听回调
private final ILocationListener mListener;
//...省略
//唯一标识
private final Object mKey;
final HashMap<String, UpdateRecord> mUpdateRecords = new HashMap<>();
//...省略
private Receiver(ILocationListener listener, PendingIntent intent, int pid, int uid,String packageName, WorkSource workSource, boolean hideFromAppOps) {
super(new CallerIdentity(uid, pid, packageName), "LocationListener");
mListener = listener;
mPendingIntent = intent;
if (listener != null) {
mKey = listener.asBinder();
} else {
mKey = intent;
}
//省略
}
//...省略
//位置改变调用接口，最终会调用到mListener.onLocationChanged
public boolean callLocationChangedLocked(Location location) {
if (mListener != null) {
try {
mListener.onLocationChanged(new Location(location));
// call this after broadcasting so we do not increment
// if we throw an exception.
incrementPendingBroadcastsLocked();
} catch (RemoteException e) {
return false;
}
}
//...省略
}
//...省略
}
由以上Receiver的分析可以知道，如果有位置变化会调用Receiver.callLocationChangedLocked(location)。
在LocationManagerService中通过"callLocationChangedLocked"定位到被调用的地方如下:
//LocationManagerService.java中的方法
private void handleLocationChangedLocked(Location location, LocationProvider provider) {
//...省略
if (!receiver.callLocationChangedLocked(notifyLocation)) {
Slog.w(TAG, "RemoteException calling onLocationChanged on "
+ receiver);
receiverDead = true;
}
//...省略
}
在LocationManagerService中通过"handleLocationChangedLocked"定位到被调用的地方在LocationProvider 类中，该类定义在LocationManagerService中。核心关键代码如下:
private class LocationProvider implements AbstractLocationProvider.LocationProviderManager {
//...省略
//根据传入的gps提供商名称创建位置提供者
private LocationProvider(String name) {
this(name, false);
}
//根据传入的gps提供商名称创建位置提供者
private LocationProvider(String name, boolean isManagedBySettings) {
mName = name;
mIsManagedBySettings = isManagedBySettings;
mProvider = null;
//...省略
}
// called from any thread
@Override
public void onReportLocation(Location location) {
// no security check necessary because this is coming from an internal-only interface
// move calls coming from below LMS onto a different thread to avoid deadlock
mHandler.post(() -> {
synchronized (mLock) {
//此处调用了
handleLocationChangedLocked(location, this);
}
});
}
//...省略
}
由以上LocationProvider的构造函数可以分析出系统初始化的时候会构造一个GPS_PROVIDER的位置提供者用来提供GPS定位服务。通过在LocationManagerService初始化的分析找到了位置提供者初始化的逻辑。相关核心代码如下:
//LocationManagerService.java文件中
//此处调用了初始化
public void systemRunning() {
synchronized (mLock) {
initializeLocked();
}
}
@GuardedBy("mLock")
private void initializeLocked() {
//...省略
// prepare providers
//调用了初始化位置提供者函数
initializeProvidersLocked();
}
private void initializeProvidersLocked() {
//...省略
if (GnssLocationProvider.isSupported()) {
// Create a gps location provider
//创建gps位置提供管理器
LocationProvider gnssProviderManager = new LocationProvider(GPS_PROVIDER, true);
mRealProviders.add(gnssProviderManager);
addProviderLocked(gnssProviderManager);
//创建Gnss位置提供者，实际的位置数据在这个provider中进行通知
GnssLocationProvider gnssProvider = new GnssLocationProvider(mContext,
gnssProviderManager,
mHandler.getLooper());
//gps位置提供管理器和gnss数据提供者关联上
gnssProviderManager.attachLocked(gnssProvider);
mGnssSystemInfoProvider = gnssProvider.getGnssSystemInfoProvider();
mGnssBatchingProvider = gnssProvider.getGnssBatchingProvider();
mGnssMetricsProvider = gnssProvider.getGnssMetricsProvider();
mGnssCapabilitiesProvider = gnssProvider.getGnssCapabilitiesProvider();
mGnssStatusProvider = gnssProvider.getGnssStatusProvider();
mNetInitiatedListener = gnssProvider.getNetInitiatedListener();
mGnssMeasurementsProvider = gnssProvider.getGnssMeasurementsProvider();
mGnssMeasurementCorrectionsProvider =
gnssProvider.getGnssMeasurementCorrectionsProvider();
mGnssNavigationMessageProvider = gnssProvider.getGnssNavigationMessageProvider();
mGpsGeofenceProxy = gnssProvider.getGpsGeofenceProxy();
}
//省略
}
通过以上位置提供者初始化的逻辑可以分析到创建的gps位置管理器使用GnssLocationProvider 来提供具体的位置更新服务。
2.3 GnssLocationProvider中位置更新通知流程分析
GnssLocationProvider源码文件路径位于:
frameworks\base\services\core\java\com\android\server\location\GnssLocationProvider.java
以下是和位置改变更新通知的核心相关代码如下:
//GnssLocationProvider 继承AbstractLocationProvider
public class GnssLocationProvider extends AbstractLocationProvider implements
InjectNtpTimeCallback,
GnssSatelliteBlacklistCallback {
//省略
//以下函数说明jni层去调用 reportLocation
@NativeEntryPoint
private void reportLocation(boolean hasLatLong, Location location) {
sendMessage(REPORT_LOCATION, hasLatLong ? 1 : 0, location);
}
//sendMessage
private void sendMessage(int message, int arg, Object obj) {
//...省略
mHandler.obtainMessage(message, arg, 1, obj).sendToTarget();
}
//mHandler 初始化
mHandler = new ProviderHandler(looper);
//ProviderHandler为Handler类型，通过他发送消息通知位置改变
private final class ProviderHandler extends Handler {
public ProviderHandler(Looper looper) {
super(looper, null, true /*async*/);
}
@Override
public void handleMessage(Message msg) {
int message = msg.what;
switch (message) {
//省略
case REPORT_LOCATION:
//此处调用位置报告函数
handleReportLocation(msg.arg1 == 1, (Location) msg.obj);
break;
//省略
}
}
// 位置报告函数实现
private void handleReportLocation(boolean hasLatLong, Location location) {
//...省略
reportLocation(location);
//...省略
}
}
以上分析可知handleReportLocation最终调用reportLocation通知位置信息变化。reportLocation方法在父类AbstractLocationProvider 中实现。如下是AbstractLocationProvider 类中reportLocation核心实现代码:
public abstract class AbstractLocationProvider {
//...省略
//LocationManagerService初始化的时候传入赋值为gps 位置提供管理器
private final LocationProviderManager mLocationProviderManager;
protected AbstractLocationProvider(
Context context, LocationProviderManager locationProviderManager) {
mContext = context;
mLocationProviderManager = locationProviderManager;
}
//reportLocation最终使用了mLocationProviderManager.onReportLocation方法
protected void reportLocation(Location location) {
mLocationProviderManager.onReportLocation(location);
}
//...省略
}
由于mLocationProviderManager在初始化的时候赋值为GPS_PROVIDER的位置提供管理者，所以mLocationProviderManager.onReportLocation调用就变成了LocationProvider.onReportLocation。
三、GnssLocationProvider 中jni处理位置改变通知分析
在上面分析中,GnssLocationProvider 提供了一个通知位置改变的java函数reportLocation(boolean hasLatLong, Location location)，该函数在jni中被调用。在GnssLocationProvider中提供了一系列native方法，比如如下:
private static native void class_init_native();
private static native boolean native_is_supported();
private static native boolean native_is_gnss_visibility_control_supported();
private static native void native_init_once(boolean reinitializeGnssServiceHandle);
private native boolean native_init();
所以源码系统中存在GnssLocationProvider的jni实现文件。在源码中找到了对应的实现文件路径如下:
frameworks\base\services\core\jni\com_android_server_location_GnssLocationProvider.cpp
以下是抽取JNI位置更新的相关核心代码部分:
1. 缓存java层中GnssLocationProvider类的reportLocation 方法ID
static jmethodID method_reportLocation;
2.定义位置改变回调接口
struct GnssCallback : public IGnssCallback {
Return<void> gnssLocationCb(const GnssLocation_V1_0& location) override;
Return<void> gnssLocationCb_2_0(const GnssLocation_V2_0& location) override;
private:
Return<void> gnssLocationCbImpl(const T& location);
};
3. 获取reportLocation方法ID,方便后面反射调用
method_reportLocation = env->GetMethodID(clazz, "reportLocation",
"(ZLandroid/location/Location;)V");
4.位置改变回调方法具体实现
template<class T> Return<void> GnssCallback::gnssLocationCbImpl(const T& location) {
JNIEnv* env = getJniEnv();
jobject jLocation = translateGnssLocation(env, location);
env->CallVoidMethod(mCallbacksObj,
method_reportLocation,
boolToJbool(hasLatLong(location)),
jLocation);
checkAndClearExceptionFromCallback(env, __FUNCTION__);
env->DeleteLocalRef(jLocation);
return Void();
}
//1.0版本位置改变回调方法，最终通过反射调用通知java层位置改变
Return<void> GnssCallback::gnssLocationCb(const GnssLocation_V1_0& location) {
return gnssLocationCbImpl<GnssLocation_V1_0>(location);
}
//2.0版本位置改变回调方法，最终通过反射调用通知java层位置改变
Return<void>
GnssCallback::gnssLocationCb_2_0(const GnssLocation_V2_0& location) {
return gnssLocationCbImpl<GnssLocation_V2_0>(location);
}
5.初始化函数中通过gps硬件抽象层设置监听回调
static jboolean android_location_GnssLocationProvider_init(JNIEnv* env, jobject obj) {
// Set top level IGnss.hal callback.
sp<IGnssCallback> gnssCbIface = new GnssCallback();
if (gnssHal_V2_0 != nullptr) {
result = gnssHal_V2_0->setCallback_2_0(gnssCbIface);
} else if (gnssHal_V1_1 != nullptr) {
result = gnssHal_V1_1->setCallback_1_1(gnssCbIface);
} else {
result = gnssHal->setCallback(gnssCbIface);
}
}
四、总结
gps位置改变监听总的流程大概如下图所示: