一：原理分析
- 主要sendExtraCommand方法中传递两个参数， 根据如下源码可以知道第一个参数传递
delete_aiding_data,第二个参数传递null即可。
@Override
public boolean sendExtraCommand(String command, Bundle extras) {
long identity = Binder.clearCallingIdentity();
boolean result = false;
if ("delete_aiding_data".equals(command)) {
result = deleteAidingData(extras);
} else if ("force_time_injection".equals(command)) {
sendMessage(INJECT_NTP_TIME, 0, null);
result = true;
} else if ("force_xtra_injection".equals(command)) {
if (mSupportsXtra) {
xtraDownloadRequest();
result = true;
}
} else {
Log.w(TAG, "sendExtraCommand: unknown command " + command);
}
Binder.restoreCallingIdentity(identity);
return result;
}
private boolean deleteAidingData(Bundle extras) {
int flags;
if (extras == null) {
flags = GPS_DELETE_ALL;
} else {
flags = 0;
if (extras.getBoolean("ephemeris")) flags |= GPS_DELETE_EPHEMERIS;
if (extras.getBoolean("almanac")) flags |= GPS_DELETE_ALMANAC;
if (extras.getBoolean("position")) flags |= GPS_DELETE_POSITION;
if (extras.getBoolean("time")) flags |= GPS_DELETE_TIME;
if (extras.getBoolean("iono")) flags |= GPS_DELETE_IONO;
if (extras.getBoolean("utc")) flags |= GPS_DELETE_UTC;
if (extras.getBoolean("health")) flags |= GPS_DELETE_HEALTH;
if (extras.getBoolean("svdir")) flags |= GPS_DELETE_SVDIR;
if (extras.getBoolean("svsteer")) flags |= GPS_DELETE_SVSTEER;
if (extras.getBoolean("sadata")) flags |= GPS_DELETE_SADATA;
if (extras.getBoolean("rti")) flags |= GPS_DELETE_RTI;
if (extras.getBoolean("celldb-info")) flags |= GPS_DELETE_CELLDB_INFO;
if (extras.getBoolean("all")) flags |= GPS_DELETE_ALL;
}
if (flags != 0) {
native_delete_aiding_data(flags);
return true;
}
return false;
}
根据flags值GPS_DELETE_ALL清除数据
static void android_location_GpsLocationProvider_delete_aiding_data(JNIEnv* /* env */,
jobject /* obj */,
jint flags)
{
if (sGpsInterface)
sGpsInterface->delete_aiding_data(flags);
}
/**
* 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);
二：实现方式
java层主要代码如下：
LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Bundle bundle = null;
locationManager.sendExtraCommand(LocationManager.GPS_PROVIDER, "force_xtra_injection", bundle);
locationManager.sendExtraCommand(LocationManager.GPS_PROVIDER, "force_time_injection", bundle);
//GPS cold start
locationManager.sendExtraCommand(LocationManager.GPS_PROVIDER, "delete_aiding_data", bundle);
所需权限配置如下， 6.0版本可能需要动态申请权限。
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_LOCATION_EXTRA_COMMANDS"/>
喜欢源码分析系列可参考其他文章：
Android源码分析（一）-----如何快速掌握Android编译文件
Android源码分析（二）-----如何编译修改后的framework资源文件
Android源码分析（三）-----系统框架设计思想
Android源码分析（四）-----Android源码编译及刷机步骤
Android源码分析（五）-----如何从架构师的角度去设计Framework框架