hardware/ril/reference-ril/reference-ril.c
static void onUnsolicited (const char *s, const char *sms_pdu)
{
 ... ...
 if (strStartsWith(s, "+CMT:")) {
  RIL_onUnsolicitedResponse (
   RIL_UNSOL_RESPONSE_NEW_SMS,        /* 上报UNSOL_RESPONSE_NEW_SMS消息 */
   sms_pdu, strlen(sms_pdu)); 
 }
 ... ...
}

hardware/ril/libril/ril.cpp
extern "C"
void RIL_onUnsolicitedResponse(int unsolResponse, void *data,
        size_t datalen)
{
 ... ...
 unsolResponseIndex = unsolResponse - RIL_UNSOL_RESPONSE_BASE; /* 找出消息在s_unsolResponses[]的索引 */
 ... ...
 switch (s_unsolResponses[unsolResponseIndex].wakeType) {   /* 禁止进入休眠 */
  case WAKE_PARTIAL:
   grabPartialWakeLock();
   shouldScheduleTimeout = true;
  break;
  ... ...
 }
 ... ...
 ret = s_unsolResponses[unsolResponseIndex]      /* 调用消息处理函数responseString() */
    .responseFunction(p, data, datalen);
 ... ...
 ret = sendResponse(p);           /* 发送Parcel中的信息内容到服务端RILJ */
}
static UnsolResponseInfo s_unsolResponses[] = { 
... ...
/* 消息对应的消息处理函数，新信息到来会唤醒系统 */
{RIL_UNSOL_RESPONSE_NEW_SMS, responseString, WAKE_PARTIAL},
... ...
}；
static int responseString(Parcel &p, void *response, size_t responselen) {
 /* one string only */
 startResponse;
 appendPrintBuf("%s%s", printBuf, (char*)response);    
 closeResponse;
 writeStringToParcel(p, (const char *)response);     /* 把字符串格式的信息存到Parcel容器中 */
 return 0;
}

frameworks/opt/telephony/src/java/com/android/internal/telephony/RIL.java
private void 
processUnsolicited (Parcel p) { 
 ... ...
 case RIL_UNSOL_RESPONSE_NEW_SMS: ret = responseString(p); break;
 ... ...
 switch(response) {
  ... ...
  case RIL_UNSOL_RESPONSE_NEW_SMS: {
   if (RILJ_LOGD) unsljLog(response);      /* 参考log：[UNSL]< UNSOL_RESPONSE_NEW_SMS */
   // FIXME this should move up a layer
   String a[] = new String[2];
   a[1] = (String)ret;
   SmsMessage sms;
   sms = SmsMessage.newFromCMT(a);       /* 解析PDU格式的短信息 */
   if (mGsmSmsRegistrant != null) {
    mGsmSmsRegistrant
     .notifyRegistrant(new AsyncResult(null, sms, null));
   }
   break;
  }
  ... ...
 }
 ... ...
}
private Object
responseString(Parcel p) { 
 String response;
 response = p.readString();               /* 信息内容转换成Object */
 return response;
}

frameworks/opt/telephony/src/java/android/telephony/SmsMessage.java
public static SmsMessage newFromCMT(String[] lines) {
 // received SMS in 3GPP format
 SmsMessageBase wrappedMessage =
   com.android.internal.telephony.gsm.SmsMessage.newFromCMT(lines);  /* 是对另一个newFromCMT的封装，因为有gsm和cdma两种短信，
                     * 即cdma中也有newFromCMT，根据情况按需选择 
                     */
 return new SmsMessage(wrappedMessage);
}
  com.android.internal.telephony.gsm.SmsMessage.newFromCMT(lines)的实现在
frameworks/opt/telephony/src/java/com/android/internal/telephony/gsm/SmsMessage.java
public class SmsMessage extends SmsMessageBase {
 ... ...
 public static SmsMessage newFromCMT(String[] lines) {
  try {
   SmsMessage msg = new SmsMessage();
   msg.parsePdu(IccUtils.hexStringToBytes(lines[1]));    /* 解析PDU短信 */
   return msg;
  } catch (RuntimeException ex) {
   Rlog.e(LOG_TAG, "SMS PDU parsing failed: ", ex);
   return null;
  }
 }
 ... ...
}
  IccUtils.hexStringToBytes(lines[1])把十六进制的字符串转换成字节数组msg.parsePdu()解析这个数组的内容，最后获得短信内容
frameworks/opt/telephony/src/java/com/android/internal/telephony/gsm/SmsMessage.java
private void parsePdu(byte[] pdu) { 
 ... ...
 mScAddress = p.getSCAddress(); 
 if (mScAddress != null) {  
  if (VDBG) Rlog.d(LOG_TAG, "SMS SC address: " + mScAddress);   /* 参考log：SMS SC address: +8613800755500 */
 }
 ... ...
 mMti = firstByte & 0x3;
 switch (mMti) {
  ... ...
   case 3: //GSM 03.40 9.2.3.1: MTI == 3 is Reserved.
     //This should be processed in the same way as MTI == 0 (Deliver)
    parseSmsDeliver(p, firstByte);         /* 对短信类型为Deliver的短信进行解析 */
    break;
   ... ...
  }
 ... ...
}
private void parseSmsDeliver(PduParser p, int firstByte) {
 ... ...
 mOriginatingAddress = p.getAddress();                            
 if (mOriginatingAddress != null) {
  if (VDBG) Rlog.v(LOG_TAG, "SMS originating address: "    /* 参考log: SMS originating address: +861371533xxxx */                     
    + mOriginatingAddress.address);                           
 }
 ... ...
 mProtocolIdentifier = p.getByte();
 // TP-Data-Coding-Scheme
 // see TS 23.038
 mDataCodingScheme = p.getByte();
 if (VDBG) {
  Rlog.v(LOG_TAG, "SMS TP-PID:" + mProtocolIdentifier
    + " data coding scheme: " + mDataCodingScheme);    /* 参考log: SMS TP-PID:0 data coding scheme: 0 */
 }
 mScTimeMillis = p.getSCTimestampMillis();
 if (VDBG) Rlog.d(LOG_TAG, "SMS SC timestamp: " + mScTimeMillis);   /* 参考log：SMS SC timestamp: 1571831129000 */
 boolean hasUserDataHeader = (firstByte & 0x40) == 0x40;
 parseUserData(p, hasUserDataHeader);          /* 解析信息有效内容 */
 ... ... 
}  
private void parseUserData(PduParser p, boolean hasUserDataHeader) {
 ... ...
 if (VDBG) Rlog.v(LOG_TAG, "SMS message body (raw): '" + mMessageBody + "'"); /* 短信内容，参考log: SMS message body (raw): 'jchfbfh' */
 ... ...
} 

frameworks/opt/telephony/src/java/com/android/internal/telephony/RIL.java
mGsmSmsRegistrant
 .notifyRegistrant(new AsyncResult(null, sms, null));        /* 把sms转成Object类型 */
frameworks/base/core/java/android/os/AsyncResult.java
public class AsyncResult
{
 ... ...
 /** please note, this sets m.obj to be this */
 public
 AsyncResult (Object uo, Object r, Throwable ex)
 {
  userObj = uo;
  result = r;
  exception = ex;
 }
 ... ...
}

frameworks/opt/telephony/src/java/com/android/internal/telephony/BaseCommands.java 
public abstract class BaseCommands implements CommandsInterface {
 ... ...
 @Override                                    
 public void setOnNewGsmSms(Handler h, int what, Object obj) {  /* mGsmSmsRegistrant.notifyRegistrant(new AsyncResult(null, sms, null))中的mGsmSmsRegistrant是在这里创建的 */                      
  mGsmSmsRegistrant = new Registrant (h, what, obj);                         
 }
 ... ...
} 

frameworks/base/core/java/android/os/Registrant.java
public class Registrant                                  
{ 
 public
 Registrant(Handler h, int what, Object obj)      /* 传入需要处理消息为what的事件处理Handler h，obj为事件内容，参考phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null); */                          
 { 
  refH = new WeakReference(h);                               
  this.what = what;                                 
  userObj = obj;                                  
 } 
 ... ...
 /**
  * This makes a copy of @param ar
  */
 public void
 notifyRegistrant(AsyncResult ar)         /* 参考mGsmSmsRegistrant.notifyRegistrant(new AsyncResult(null, sms, null)) */
 {
  internalNotifyRegistrant (ar.result, ar.exception);   /* ar.result为sms */
 }
 /*package*/ void
 internalNotifyRegistrant (Object result, Throwable exception)  /* internalNotifyRegistrant (sms, Throwable exception) */
 {
  Handler h = getHandler();
  if (h == null) {
   clear();
  } else {
   Message msg = Message.obtain();       /* 创建一个消息 */
   msg.what = what;           /* 消息类型EVENT_NEW_SMS */
   msg.obj = new AsyncResult(userObj, result, exception); /* 消息内容sms */
   h.sendMessage(msg);          /* 发送消息到注册了这个消息的Handler，参考phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null);的getHandler() */
  }
 }
 ... ...
} 

./frameworks/opt/telephony/src/java/com/android/internal/telephony/ImsSMSDispatcher.java
public final class ImsSMSDispatcher extends SMSDispatcher {
 ... ...
 mGsmInboundSmsHandler = GsmInboundSmsHandler.makeInboundSmsHandler(phone.getContext(),   /* 获取mGsmInboundSmsHandler，并启动状态机 */
   storageMonitor, phone); 
 ... ...
}
./frameworks/opt/telephony/src/java/com/android/internal/telephony/gsm/GsmInboundSmsHandler.java
public class GsmInboundSmsHandler extends InboundSmsHandler {
 ... ...
 /**
  * Create a new GSM inbound SMS handler.
  */
 private GsmInboundSmsHandler(Context context, SmsStorageMonitor storageMonitor,
   PhoneBase phone) {
  super("GsmInboundSmsHandler", context, storageMonitor, phone,        /* 构造GsmInboundSmsHandler时，通过super()调用InboundSmsHandler的构造函数 */
    GsmCellBroadcastHandler.makeGsmCellBroadcastHandler(context, phone));
  phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null);        /* 注册EVENT_NEW_SMS消息 */
  mDataDownloadHandler = new UsimDataDownloadHandler(phone.mCi);
 }
 ... ...
 /** 
  * Wait for state machine to enter startup state. We can't send any messages until then.
  */
 public static GsmInboundSmsHandler makeInboundSmsHandler(Context context,
   SmsStorageMonitor storageMonitor, PhoneBase phone) {
  GsmInboundSmsHandler handler = new GsmInboundSmsHandler(context, storageMonitor, phone); /* 实例化GsmInboundSmsHandler */
  handler.start();                   /* 抽象类InboundSmsHandler继承与StateMachine，而GsmInboundSmsHandler继承于InboundSmsHandler，
                         * GsmInboundSmsHandler调用启动状态机方法start()
                         */
  return handler;
 }
 ... ...
}
./frameworks/opt/telephony/src/java/com/android/internal/telephony/InboundSmsHandler.java
public abstract class InboundSmsHandler extends StateMachine {
 ... ...
 protected InboundSmsHandler(String name, Context context, SmsStorageMonitor storageMonitor,
   PhoneBase phone, CellBroadcastHandler cellBroadcastHandler) {
  ... ...
  addState(mDefaultState);                 /* 构造InboundSmsHandler时，添加状态机的状态 */
  addState(mStartupState, mDefaultState);
  addState(mIdleState, mDefaultState);
  addState(mDeliveringState, mDefaultState);
  addState(mWaitingState, mDeliveringState);
  setInitialState(mStartupState);               /* 初始化状态机 */
  if (DBG) log("created InboundSmsHandler");
 }
 ... ... 
 class IdleState extends State {
  @Override
  public void enter() {
   if (DBG) log("entering Idle state");
   sendMessageDelayed(EVENT_RELEASE_WAKELOCK, WAKELOCK_TIMEOUT);
  }
  @Override
  public void exit() {
   mWakeLock.acquire();
   if (DBG) log("acquired wakelock, leaving Idle state");
  }
  @Override
  public boolean processMessage(Message msg) {
   if (DBG) log("Idle state processing message type " + msg.what);
   switch (msg.what) {
    case EVENT_NEW_SMS:                /* 空闲时，接收到短信 */
    case EVENT_BROADCAST_SMS:
     deferMessage(msg);
     transitionTo(mDeliveringState);            /* 转到mDeliveringState */
     return HANDLED;
    ... ...
   }
  }
 } 
  ... ...
 class DeliveringState extends State {               /* 转到mDeliveringState状态 */
  @Override
  public void enter() {
   if (DBG) log("entering Delivering state");
  }
  @Override
  public void exit() {
   if (DBG) log("leaving Delivering state");
  }
  @Override
  public boolean processMessage(Message msg) {
   switch (msg.what) {
    case EVENT_NEW_SMS:
     // handle new SMS from RIL
     handleNewSms((AsyncResult) msg.obj);           /* 处理新SMS */
     sendMessage(EVENT_RETURN_TO_IDLE);            /* 处理完回到空闲状态 */
     return HANDLED;
    ... ...
   }
  } 
   ... ...
 }
}
void handleNewSms(AsyncResult ar) {
 ... ...
 SmsMessage sms = (SmsMessage) ar.result;
 result = dispatchMessage(sms.mWrappedSmsMessage);
 ... ...
}
public int dispatchMessage(SmsMessageBase smsb) {
 ... ...
 return dispatchMessageRadioSpecific(smsb);
 ... ...
}

./frameworks/opt/telephony/src/java/com/android/internal/telephony/InboundSmsHandler.java 
 
 
class DeliveringState extends State {
 ... ...
 public boolean processMessage(Message msg) {
  switch (msg.what) {
   ... ...
   case EVENT_BROADCAST_SMS:               /* 接收到EVENT_BROADCAST_SMS消息并处理 */
    // if any broadcasts were sent, transition to waiting state
    if (processMessagePart((InboundSmsTracker) msg.obj)) {
     transitionTo(mWaitingState);
    }
    return HANDLED;
   ... ...
  }
 }
 ... ...
 
}
 
boolean processMessagePart(InboundSmsTracker tracker) {
 ... ...
 BroadcastReceiver resultReceiver = new SmsBroadcastReceiver(tracker);     /* 创建一个广播接收者，用来处理短信广播的结果 */
 ... ...
 intent = new Intent(Intents.SMS_DELIVER_ACTION);           /* 设置当前intent的action为SMS_DELIVER_ACTION */
 
 // Direct the intent to only the default SMS app. If we can't find a default SMS app
 // then sent it to all broadcast receivers.
 ComponentName componentName = SmsApplication.getDefaultSmsApplication(mContext, true); /* 这个action只会发送给carrier app，而且carrier app可以通过set result为RESULT_CANCELED来终止这个广播 */
 if (componentName != null) {
  // Deliver SMS message only to this receiver
  intent.setComponent(componentName);
  log("Delivering SMS to: " + componentName.getPackageName() +
    " " + componentName.getClassName());
 }
 ... ...
 dispatchIntent(intent, android.Manifest.permission.RECEIVE_SMS,       /* 广播intent */
    AppOpsManager.OP_RECEIVE_SMS, resultReceiver);
 ... ...
}
 
 
private final class SmsBroadcastReceiver extends BroadcastReceiver {
 ... ... 
 public void onReceive(Context context, Intent intent) {
  ... ...
  // Now that the intents have been deleted we can clean up the PDU data.
  if (!Intents.DATA_SMS_RECEIVED_ACTION.equals(action)
    && !Intents.DATA_SMS_RECEIVED_ACTION.equals(action)
    && !Intents.WAP_PUSH_RECEIVED_ACTION.equals(action)) {
   loge("unexpected BroadcastReceiver action: " + action);
  }
 
  int rc = getResultCode();
  if ((rc != Activity.RESULT_OK) && (rc != Intents.RESULT_SMS_HANDLED)) {
   loge("a broadcast receiver set the result code to " + rc
     + ", deleting from raw table anyway!");
  } else if (DBG) {
   log("successful broadcast, deleting from raw table.");
  }
 
  deleteFromRawTable(mDeleteWhere, mDeleteWhereArgs);
  sendMessage(EVENT_BROADCAST_COMPLETE);            /* 成功广播 */
 
  ... ...
 }
 ... ...
}