Android FM模块学习之三 FM手动调频

前一章我们学习了FM的自动调频，接下来我们就看看FM手动调频是如何进行的。如果不清楚FM自动调频的过程，请打开超链接查看FM搜索频率流程。

首先来看一下流程图：

2.滑动刻度盘HorizontalNumberPicker控件在监听事件里使用方法valueToFrequency(newVal)

1.长按左右箭头居中的频率字符串，弹出FrequencyPickerDialog调频对话框确定调用tuneRadio(frequency)调频。

获取到频率

protected int valueToFrequency(int value) {
       mFrequency = mPrefs.getLowerLimit() + value *
                             mPrefs.getFrequencyStepSize();
       return mFrequency;
   }

发送一个handler 回调一个tuneRadio(frequency)调频。

Runnable mRadioChangeFrequency = new Runnable(){
       public void run() {
           mUpdatePickerValue = false;
           tuneRadio(mFrequency);
       }
   };

3.手动点击按钮左右箭头, 通过监听调用：

int frequency =FmSharedPreferences.getNextTuneFrequency();

int frequency =FmSharedPreferences.getPrevTuneFrequency();

tuneRadio(frequency);进行调频

getNextTuneFrequency()方法通过判断频率最大限制范围，后加200（刻度）

getPrevTuneFrequency()方法通过判断频率最小限制范围，后减200（刻度）

调频方法分析

private void tuneRadio(int frequency)

private void tuneRadio(int frequency){
      /* Issue the tune command only if tuneCommand is already not active */
      if((mService != null) && (mCommandActive != CMD_TUNE) && isFmOn()) {
         boolean bStatus = false;
         try {
             bStatus = mService.tune(frequency);
             if (bStatus) {
                 postTimeoutHandler(CMD_TUNE);
             }else {
               if (isFmOn()) {
                  mCommandFailed = CMD_TUNE;
                  Log.e(LOGTAG, "mService.tune failed");
                  showDialog(DIALOG_CMD_FAILED);
               }
             }mTunedStation.setName("");
             mTunedStation.setPI(0);
             mTunedStation.setPty(0);
             updateStationInfoToUI();
         }catch (RemoteException e) {
            e.printStackTrace();
         }
      }else {
         Log.e(LOGTAG, "Delayed Tune handler stopped");
      }
   }

通过回调引用类调用FMRadioService类的tune()方法进行调频

bStatus = mService.tune(frequency);

发送一个广播连接是否超时

postTimeoutHandler(CMD_TUNE);

设置调频名字，更新FMRadioUI界面信息

mTunedStation.setName("");

mTunedStation.setPI(0);

mTunedStation.setPty(0);

updateStationInfoToUI()

（通过IFMRadioSrevice.aidl通信机制onbind返回的类的引用调用FMRadioService中的调频方法）

FMRadioService中的tune方法

public boolean tune(int frequency)

public boolean tune(int frequency) {
      boolean bCommandSent=false;
      double doubleFrequency = frequency/1000.00;

      Log.d(LOGTAG, "tuneRadio:  " + doubleFrequency);
      if (mReceiver != null)
      {
         mReceiver.setStation(frequency);
         bCommandSent = true;
      }
      return bCommandSent;
   }

调用FMReceiver类的setStation方法调频

public boolean setStation (intfrequencyKHz)

public boolean setStation (int frequencyKHz) {
      int ret;

      mControl.setFreq(frequencyKHz);
      ret = mControl.setStation(sFd);
      if(ret < 0 )
      {
         return false;
      }
      else
      {
         return true;
      }
   }

调用FMRxControls类（FM读取控制台信息）设置频率

mControl.setFreq(frequencyKHz);

设置优化调频核心指定的频率

ret = mControl.setStation(sFd);

  public int setStation(int fd) {
      Log.d(TAG, "** Tune Using: "+fd);
      int ret = FmReceiverJNI.setFreqNative(fd, mFreq);
      Log.d(TAG, "** Returned: "+ret);
      return ret;
   }

最后调用FmReceiverJNI类

setFreqNative(fd, mFreq); 本地方法 JNI到 cpp文件

/*native interface */
static jint android_hardware_fmradio_FmReceiverJNI_setFreqNative
    (JNIEnv * env, jobject thiz, jint fd, jint freq)
{
    int err;
    double tune;
    struct v4l2_frequency freq_struct;
    freq_struct.type = V4L2_TUNER_RADIO;
    freq_struct.frequency = (freq*TUNE_MULT/1000);
    err = ioctl(fd, VIDIOC_S_FREQUENCY, &freq_struct);
    if(err < 0){
            return FM_JNI_FAILURE;
    }
    return FM_JNI_SUCCESS;
}