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;
}
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作者：护士leo
来源：CSDN
原文：
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