Android中的信号强度上报与显示完整流程

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Android中的信号强度上报与显示完整流程
红狼博客
分析：
在RILConstants.java中找到：
int RIL_UNSOL_SIGNAL_STRENGTH = 1009;

在RIL.java中找到与其相关的代码：
private void
processUnsolicited (Parcel p) {
…….
case RIL_UNSOL_SIGNAL_STRENGTH: ret = responseSignalStrength(p); break;
…..
case RIL_UNSOL_SIGNAL_STRENGTH:
// Note this is set to “verbose” because it happens
// frequently
if (RILJ_LOGV) unsljLogvRet(response, ret);

if (mSignalStrengthRegistrant != null) {
mSignalStrengthRegistrant.notifyRegistrant(
new AsyncResult (null, ret, null));
}

在RIL的父类BaseCommands.java中找到：
public void setOnSignalStrengthUpdate(Handler h, int what, Object obj) {
mSignalStrengthRegistrant = new Registrant (h, what, obj);
}

再找其调用者(GsmServiceStateTracker.java)：
public GsmServiceStateTracker(GSMPhone phone) {
super();

……
cm.setOnSignalStrengthUpdate(this, EVENT_SIGNAL_STRENGTH_UPDATE, null);
……

GsmServiceStateTracker自己处理上报上来的信号强度信息：
case EVENT_SIGNAL_STRENGTH_UPDATE:
// This is a notification from
// CommandsInterface.setOnSignalStrengthUpdate

ar = (AsyncResult) msg.obj;

// The radio is telling us about signal strength changes
// we don’t have to ask it
dontPollSignalStrength = true;

onSignalStrengthResult(ar);
break;

函数onSignalStrengthResult负责处理：
private void onSignalStrengthResult(AsyncResult ar) {
SignalStrength oldSignalStrength = mSignalStrength;
int rssi = 99;

if (ar.exception != null) {
// -1 = unknown
// most likely radio is resetting/disconnected
setSignalStrengthDefaultValues();
} else {
int[] ints = (int[])ar.result;

// bug 658816 seems to be a case where the result is 0-length
if (ints.length != 0) {
rssi = ints[0];
} else {
Log.e(LOG_TAG, “Bogus signal strength response”);
rssi = 99;
}
}

mSignalStrength = new SignalStrength(rssi, -1, -1, -1,
-1, -1, -1, true);

if (!mSignalStrength.equals(oldSignalStrength)) {
try { // This takes care of delayed EVENT_POLL_SIGNAL_STRENGTH (scheduled after
// POLL_PERIOD_MILLIS) during Radio Technology Change)
phone.notifySignalStrength();
} catch (NullPointerException ex) {
log(“onSignalStrengthResult() Phone already destroyed: ” + ex
+ “SignalStrength not notified”);
}
}
}

若没发生异常，且值产生变化，则调用 phone.notifySignalStrength通知（见GSMPhone.java）：
notifySignalStrength() {
mNotifier.notifySignalStrength(this);
}

DefaultPhoneNotifier（DefaultPhoneNotifier.java）通知注册者：
public void notifySignalStrength(Phone sender) {
try {
mRegistry.notifySignalStrength(sender.getSignalStrength());
} catch (RemoteException ex) {
// system process is dead
}
}

这个注册者来自：
DefaultPhoneNotifier() {
mRegistry = ITelephonyRegistry.Stub.asInterface(ServiceManager.getService(
“telephony.registry”));
}

TelephonyRegistry.java，TelephonyRegistry是ITelephonyRegistry.Stub的子类，作为service运行在system_server进程中，它会通知注册者。上面的DefaultPhoneNotifier运行在com.android.phone进程中，当信号强度值变化时，通过Service进行通知（service被感兴趣的注册者调用了listen，添加了回调函数。
public void notifySignalStrength(SignalStrength signalStrength) {
if (!checkNotifyPermission(“notifySignalStrength()”)) {
return;
}
synchronized (mRecords) {
mSignalStrength = signalStrength;
for (int i = mRecords.size() – 1; i >= 0; i–) {
Record r = mRecords.get(i);
if ((r.events & PhoneStateListener.LISTEN_SIGNAL_STRENGTHS) != 0) {
sendSignalStrength(r, signalStrength);
}
if ((r.events & PhoneStateListener.LISTEN_SIGNAL_STRENGTH) != 0) {
try {
int gsmSignalStrength = signalStrength.getGsmSignalStrength();
r.callback.onSignalStrengthChanged((gsmSignalStrength == 99 ? -1
: gsmSignalStrength));
} catch (RemoteException ex) {
remove(r.binder);
}
}
}
}
broadcastSignalStrengthChanged(signalStrength);
}

在TelephonyManager.java中提供了API，应用程序可以监听各种事件，实际上它将感兴趣的监听者作为一条记录添加到service一侧的列表（跨进程）中，当有变化时，调用它们提供的回调函数，通知（跨进程）这些注册者。
TelephonyManager.java中的listen函数如下：
public void listen(PhoneStateListener listener, int events) {
String pkgForDebug = mContext != null ? mContext.getPackageName() : “<unknown>”;
try {
Boolean notifyNow = (getITelephony() != null);
mRegistry.listen(pkgForDebug, listener.callback, events, notifyNow);
} catch (RemoteException ex) {
// system process dead
} catch (NullPointerException ex) {
// system process dead
}
}
其中回调对象实例listener.callback来自于PhoneStateListener.java嵌套定义及其实例，这样，当TelephonyRegistry.java调用回调函数时，就调用到listener.callback，进而发送消息给PhoneStateListener.java中的mHandler，由其处理，进而由其子类去处理。

在StatusBarPolicy.java中，注册了下面要监听处理的事件。第二个为信号强度：
((TelephonyManager)mContext.getSystemService(Context.TELEPHONY_SERVICE))
.listen(mPhoneStateListener,
PhoneStateListener.LISTEN_SERVICE_STATE
| PhoneStateListener.LISTEN_SIGNAL_STRENGTHS
| PhoneStateListener.LISTEN_CALL_STATE
| PhoneStateListener.LISTEN_DATA_CONNECTION_STATE
| PhoneStateListener.LISTEN_DATA_ACTIVITY);

处理者为：
private PhoneStateListener mPhoneStateListener = new PhoneStateListener() {
@Override
public void onSignalStrengthsChanged(SignalStrength signalStrength) {
mSignalStrength = signalStrength;
updateSignalStrength();
}

在StatusBarPolicy的updateSignalStrength函数中，将根据得到的信息，设置适当的图标id，显示合适的图标。

主动请求：

GsmServiceStateTracker.java
case EVENT_POLL_SIGNAL_STRENGTH:
// Just poll signal strength…not part of pollState()

cm.getSignalStrength(obtainMessage(EVENT_GET_SIGNAL_STRENGTH));
break;

在RIL.java中，发送请求：
public void
getSignalStrength (Message result) {
RILRequest rr
= RILRequest.obtain(RIL_REQUEST_SIGNAL_STRENGTH, result);

/*if (RILJ_LOGD)*/ riljLog(rr.serialString() + “> ” + requestToString(rr.mRequest));

send(rr);
}

请求号在RIL.java中，定义了请求号：
RIL_REQUEST_SIGNAL_STRENGTH

返回结果： processSolicited中得到结果后sendToTarget
private void
processSolicited (Parcel p) {
…..

case RIL_REQUEST_SIGNAL_STRENGTH: ret = responseSignalStrength(p); break;

在GsmServiceStateTracker.java中，msg的handler指定为this，所以GsmServiceStateTracker负责回送的消息的处理：
case EVENT_GET_SIGNAL_STRENGTH:
// This callback is called when signal strength is polled
// all by itself

if (!(cm.getRadioState().isOn()) || (cm.getRadioState().isCdma())) {
// Polling will continue when radio turns back on and not CDMA
return;
}
ar = (AsyncResult) msg.obj;
onSignalStrengthResult(ar);
queueNextSignalStrengthPoll();

break;

private void onSignalStrengthResult(AsyncResult ar) {
SignalStrength oldSignalStrength = mSignalStrength;
int rssi = 99;
Log.d(“YCG”, “query done! onSignalStrengthResult”);
if (ar.exception != null) {
// -1 = unknown
// most likely radio is resetting/disconnected
setSignalStrengthDefaultValues();
} else {
int[] ints = (int[])ar.result;

// bug 658816 seems to be a case where the result is 0-length
if (ints.length != 0) {
rssi = ints[0];
Log.d(“YCG”, “query done! rssi=”+rssi);
} else {
Log.e(LOG_TAG, “Bogus signal strength response”);
rssi = 99;
}
}

mSignalStrength = new SignalStrength(rssi, -1, -1, -1,
-1, -1, -1, true);

if (!mSignalStrength.equals(oldSignalStrength)) {
try { // This takes care of delayed EVENT_POLL_SIGNAL_STRENGTH (scheduled after
// POLL_PERIOD_MILLIS) during Radio Technology Change)
phone.notifySignalStrength();
} catch (NullPointerException ex) {
log(“onSignalStrengthResult() Phone already destroyed: ” + ex
+ “SignalStrength not notified”);
}
}
}

phone.notifySignalStrength();通知上层，走上相同流程

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