Android中FMRadio实现

转自：http://qiuzhenqing.blog.edu.cn/2010/576669.html。作者：qiuzhenqing

目前android还没有有关FMRadio的application接口类，下面对目前存在的一个实现案例进行分析。

硬件: BCM4329 + CPCAP

要求：BCM4327需要连接RX天线

audio analog out与CPCAP相连

软件：

FMRadio.apk --> Java应用

libfmradio_jni.so : frameworks/base/fmradio/jni --> Jni

libfmradioplayer.so ： --> HAL

libfmradiostackservice.so : --> HAL

libFMRadio.so 这是实现FM的基本功能库比如搜台依赖于libbluetooth libutils 之所以跟蓝牙相关，是因为BCM4329是个蓝牙+WIFI+FM的合成芯片，FM与蓝牙共用电源，发命令共用一个HCI。

libaudio.so

首先，在init.rc中，需要启动一个FM服务,这里叫fmradio，可执行文件叫fmradioserver

service fmradio /system/bin/fmradioserver

group bluetooth

fmradioserver的代码示例：

int main(int argc, char** argv)

{

....

FMRadioStackService::instantiate(); // start the fmradio.stack service

....

}

FMRadioStackService.cpp

void FMRadioStackService::instantiate() {

defaultServiceManager()->addService(

String16("fmradio.stack"), new FMRadioStackService());

}

通过这个FMRadioStackService类，FM的基本功能已经可用

class FMRadioStackService : public BnFMRadioStackService, protected Thread

{

public:

static void instantiate();

。。。

virtual bool powerOnDevice();

virtual bool powerOffDevice();

virtual void setFMRadioPlayerClient(const sp& client);

virtual bool open();

virtual bool getBand() const;

virtual bool setBand(RADIO_BAND bind);

virtual bool tune(unsigned int freq);

virtual bool currentFreq() const;

virtual bool setAudioMode(AUDIO_MODE mode);

virtual bool getAudioMode() const;

virtual bool seek(SEEK_DIRECTION direction);

virtual bool stopSeek();

virtual bool setVolume(unsigned int vol);

virtual bool getVolume() const;

virtual bool setEmphasisFilter(EMPHASIS_FILTER filter);

virtual bool getEmphasisFilter() const;

virtual bool setMute(MUTE_MODE mode);

virtual bool isMute() const;

virtual bool enableAudioTarget(AUDIO_TARGET val); // should be called after set band;

virtual bool disableAudioTarget(AUDIO_TARGET val);

virtual bool getRssiLevel();

virtual int getChipsetId();

virtual bool close();

static void fm_int_handler(FMRadio_Msgs_t, int, int, char*);

private:

sp m_client;

。。。。

};

FMRadioStackService继承了BnFMRadioStackService， BnFMRadioStackService继承了BBinder与IFMRadioStackService,实现了onTransact()。如果把整个FMRadio看作是Client/Server模式的话，Server端就算完成了。这里有一个私有成员变量m_client显得比较奇怪，其实它是用来向上notify状态的，通过virtual void setFMRadioPlayerClient(const sp& client)赋值。

根据binder机制，我们知道一定会有一个BpFMRadioStackService，它继承BBinder与IFMRadioStackService,通过remote()->transact()实现IFMRadioStackService接口，给Client上层提供各种FMRadio功能的调用,当然remote()->transact()通过BnFMRadioStackService调到了真正的底层服务。

通过JNI gMethods

static JNINativeMethod gMethods[] = {

{"powerOnDevice", "()Z", (void*)fmradio_powerOn },

{"powerOffDevice", "()Z", (void*)fmradio_powerOff },

{"open", "()Z", (void*)fmradio_open },

{"getBand", "()Z", (void*)fmradio_getBand },

{"setBand", "(I)Z", (void*)fmradio_setBand },

{"tune", "(I)Z", (void*)fmradio_tune },

{"currentFreq", "()Z", (void*)fmradio_currentFreq },

{"setAudioMode", "(I)Z", (void*)fmradio_setAudioMode },

{"getAudioMode", "()Z", (void*)fmradio_getAudioMode },

{"seek", "(I)Z", (void*)fmradio_seek },

{"stopSeek", "()Z", (void*)fmradio_stopSeek },

{"setVolume", "(I)Z", (void*)fmradio_setVolume },

{"getVolume", "()Z", (void*)fmradio_getVolume },

{"setEmphasisFilter", "(I)Z", (void*)fmradio_setEmphasisFilter },

{"getEmphasisFilter", "()Z", (void*)fmradio_getEmphasisFilter },

{"setMute", "(I)Z", (void*)fmradio_setMute },

{"isMute", "()Z", (void*)fmradio_isMute },

{"enableAudioTarget", "(I)Z", (void*)fmradio_enableAudioTarget },

{"disableAudioTarget","(I)Z", (void*)fmradio_disableAudioTarget },

{"close", "()Z", (void*)fmradio_close },

{"native_setup", "(Ljava/lang/Object;)V", (void*)fmradio_native_setup },

{"native_finalize", "()V", (void*)fmradio_native_finalize }

};

加上registerNativeMethods

if(AndroidRuntime::registerNativeMethods(env, "com/motorola/fmradio/FMRadioPlayer", gMethods, NELEM(gMethods))>= 0) {

result = JNI_VERSION_1_4;

}

我们把com.motorola.fmradio.FMRadioPlayer这个FM类提供给了application developer.

当然，你还需要写一个FMRadioPlayer.cpp 把这些native方法申明一下。

以下的故事应该从native_setup开始，因为它绑定了fmradio.stack服务，所以它被放在了FMRadioPlayer的构造函数中。

JNIEXPORT void JNICALL fmradio_native_setup(JNIEnv *env, jobject obj, jobject weak_this)

{

LOGI("IN JNI fmradio_native_setup/n");

sp fmstack = getFMRadioStackService();//这里会有binder = sm->getService(String16("fmradio.stack"));

。。。

}

以后的应用层内容（略）

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