Android源码分析（十五）----GPS冷启动实现原理分析

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

巴特西

Android源码分析（十五）----GPS冷启动实现原理分析

一：原理分析

二：实现方式

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