关于android 4.4短信(sms)接收流程-状态机篇

google从4.4版本开始，为了解决重复接收多条短信问题，在短信接收的框架层中增加了一个状态机专门用来接收短信。

首先什么是状态机，这里不多说，网上已经有很多相关的文章，这边引用一个：http://blog.csdn.net/pi9nc/article/details/27503071。如果想直接看源码了解的。可以看StateMachine.java (frameworks\base\core\java\com\android\internal\util)

这里我分几部分来讲短信接收过程中的状态机，

一，涉及到的源文件：

GsmInboundSmsHandler.java (frameworks\opt\telephony\src\java\com\android\internal\telephony\gsm)

InboundSmsHandler.java (frameworks\opt\telephony\src\java\com\android\internal\telephony)

InboundSmsTracker.java (frameworks\opt\telephony\src\java\com\android\internal\telephony)

针对于3gpp规范的短信，基本上就是以上两支文件。对于3gpp2规范的短信，文件会有所差异。

这里的CdmaInboundSmsHandler即为3gpp2规范短信的内容。这次不会涉及这个class.

二，短信接收流程，

1，在GsmInboundSmsHandler的构造方法里：

 phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null);

这一句很关键，这是在告诉RILJ，当有新短信来的时候，RILJ会把短信发给GsmInboundSmsHandler，实际上是由其父类处理。也就是InboundSmsHandler.

2,我们看一下InboundSmsHandler到底是什么：

public abstract class InboundSmsHandler extends StateMachine {

这下清楚了。这就是接收短信的状态机。短信到达framework层后，首先由这个状态机接收。

我们再来看一上这个状态机长什么样：

当状态机初始化好后，会停留在Idle状态。当短信到来的时候，首先会由Idle状态接收到，之后就会按以下流程进行处理

这两张状态图怎么看呢，我们先来看startup状态的源码：

 class StartupState extends State {        @Override        public boolean processMessage(Message msg) {            switch (msg.what) {                case EVENT_NEW_SMS:                case EVENT_BROADCAST_SMS:                    deferMessage(msg);                    return HANDLED;                case EVENT_START_ACCEPTING_SMS:                    transitionTo(mIdleState);                    return HANDLED;

当SmsBroadcastUndelivered处理好table后，会发出EVENT_START_ACCEPTING_SMS.这时候，会从StartupState状态切到Idle状态。只有在Idle状态，才可以处理短信。

回到前面，我们最初在GsmInboundSmsHandler的构造方法里：

 phone.mCi.setOnNewGsmSms(getHandler(), EVENT_NEW_SMS, null);

也就是说当RILJ有短信的时候，会向GsmInboundSmsHandler发送EVENT_NEW_SMS,

现在这里讲的就是在Idle状态下收到了EVENT_NEW_SMS。我们接着看

  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:                case EVENT_BROADCAST_SMS:                    deferMessage(msg);                    transitionTo(mDeliveringState);                    return HANDLED;

在Idle状态收到后event_new_sms后，接着将状态切到DeliveringState.

    class DeliveringState extends State {        @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);                    sendMessage(EVENT_RETURN_TO_IDLE);                    return HANDLED;

在DeliveringState状态下，终于看到处理短信的方法了：handleNewSms:

  void handleNewSms(AsyncResult ar) {        if (ar.exception != null) {            loge("Exception processing incoming SMS: " + ar.exception);            return;        }        int result;        try {            SmsMessage sms = (SmsMessage) ar.result;//首先把短信读出来            result = dispatchMessage(sms.mWrappedSmsMessage);调用<span style="font-family: Arial, Helvetica, sans-serif;">dispatchMessage</span>        } catch (RuntimeException ex) {            loge("Exception dispatching message", ex);            result = Intents.RESULT_SMS_GENERIC_ERROR;        }        // RESULT_OK means that the SMS will be acknowledged by special handling,        // e.g. for SMS-PP data download. Any other result, we should ack here.        if (result != Activity.RESULT_OK) {            boolean handled = (result == Intents.RESULT_SMS_HANDLED);            notifyAndAcknowledgeLastIncomingSms(handled, result, null);        }    }

    public int dispatchMessage(SmsMessageBase smsb) {        // If sms is null, there was a parsing error.        if (smsb == null) {            loge("dispatchSmsMessage: message is null");            return Intents.RESULT_SMS_GENERIC_ERROR;        }        if (mSmsReceiveDisabled) {            // Device doesn't support receiving SMS,            log("Received short message on device which doesn't support "                    + "receiving SMS. Ignored.");            return Intents.RESULT_SMS_HANDLED;        }        return dispatchMessageRadioSpecific(smsb);    }

我们接着看dispatchMessageRadioSpecific：

注意，这个方法的实现在GsmInboundSmsHandler，不在是它的父类。

    protected int dispatchMessageRadioSpecific(SmsMessageBase smsb) {        SmsMessage sms = (SmsMessage) smsb;        if (sms.isTypeZero()) {//判断这个是不是typezero类型的短信。关于typezero。可以看规范<span style="font-family: Arial, Helvetica, sans-serif;">3GPP TS 23.040 ，进3gpp官网下载该规范即可</span>            // As per 3GPP TS 23.040 9.2.3.9, Type Zero messages should not be            // Displayed/Stored/Notified. They should only be acknowledged.            log("Received short message type 0, Don't display or store it. Send Ack");            return Intents.RESULT_SMS_HANDLED;        }        // Send SMS-PP data download messages to UICC. See 3GPP TS 31.111 section 7.1.1.        if (sms.isUsimDataDownload()) {            UsimServiceTable ust = mPhone.getUsimServiceTable();            return mDataDownloadHandler.handleUsimDataDownload(ust, sms);        }        boolean handled = false;        if (sms.isMWISetMessage()) {//这里wmi，有关语音信箱的短信。            mPhone.setVoiceMessageWaiting(1, -1);  // line 1: unknown number of msgs waiting            handled = sms.isMwiDontStore();            if (DBG) log("Received voice mail indicator set SMS shouldStore=" + !handled);        } else if (sms.isMWIClearMessage()) {            mPhone.setVoiceMessageWaiting(1, 0);   // line 1: no msgs waiting            handled = sms.isMwiDontStore();            if (DBG) log("Received voice mail indicator clear SMS shouldStore=" + !handled);        }        if (handled) {            return Intents.RESULT_SMS_HANDLED;        }        if (!mStorageMonitor.isStorageAvailable() &&                sms.getMessageClass() != SmsConstants.MessageClass.CLASS_0) {            // It's a storable message and there's no storage available.  Bail.            // (See TS 23.038 for a description of class 0 messages.)            return Intents.RESULT_SMS_OUT_OF_MEMORY;        }        return dispatchNormalMessage(smsb);//看这里    }

 protected int dispatchNormalMessage(SmsMessageBase sms) {        SmsHeader smsHeader = sms.getUserDataHeader();        InboundSmsTracker tracker;        if ((smsHeader == null) || (smsHeader.concatRef == null)) {            // Message is not concatenated.            int destPort = -1;            if (smsHeader != null && smsHeader.portAddrs != null) {                // The message was sent to a port.                destPort = smsHeader.portAddrs.destPort;                if (DBG) log("destination port: " + destPort);            }            tracker = new InboundSmsTracker(sms.getPdu(), sms.getTimestampMillis(), destPort,                    is3gpp2(), false);        } else {            // Create a tracker for this message segment.            SmsHeader.ConcatRef concatRef = smsHeader.concatRef;            SmsHeader.PortAddrs portAddrs = smsHeader.portAddrs;            int destPort = (portAddrs != null ? portAddrs.destPort : -1);            tracker = new InboundSmsTracker(sms.getPdu(), sms.getTimestampMillis(), destPort,                    is3gpp2(), sms.getOriginatingAddress(), concatRef.refNumber,                    concatRef.seqNumber, concatRef.msgCount, false);        }        if (VDBG) log("created tracker: " + tracker);        return addTrackerToRawTableAndSendMessage(tracker);    }

InboundSmsTracker终于出场了。这里不多说，就是把短信封装到InboundSmsTracker。接着看addTrackerToRawTableAndSendMessage：

  protected int addTrackerToRawTableAndSendMessage(InboundSmsTracker tracker) {        switch(addTrackerToRawTable(tracker)) {        case Intents.RESULT_SMS_HANDLED:            sendMessage(EVENT_BROADCAST_SMS, tracker);            return Intents.RESULT_SMS_HANDLED;        case Intents.RESULT_SMS_DUPLICATED:            return Intents.RESULT_SMS_HANDLED;        case Intents.RESULT_SMS_GENERIC_ERROR:        default:            return Intents.RESULT_SMS_GENERIC_ERROR;        }    }

这里有个很重要的方法，千万别漏掉addTrackerToRawTable。它是把短信放入raw表里。什么是raw表，打开短信数据库看一下就懂了。

 private int addTrackerToRawTable(InboundSmsTracker tracker) {        if (tracker.getMessageCount() != 1) {            // check for duplicate message segments            Cursor cursor = null;            try {                // sequence numbers are 1-based except for CDMA WAP, which is 0-based                int sequence = tracker.getSequenceNumber();                // convert to strings for query                String address = tracker.getAddress();                String refNumber = Integer.toString(tracker.getReferenceNumber());                String count = Integer.toString(tracker.getMessageCount());                String seqNumber = Integer.toString(sequence);                // set the delete selection args for multi-part message                String[] deleteWhereArgs = {address, refNumber, count};                tracker.setDeleteWhere(SELECT_BY_REFERENCE, deleteWhereArgs);                // Check for duplicate message segments                cursor = mResolver.query(sRawUri, PDU_PROJECTION,                        "address=? AND reference_number=? AND count=? AND sequence=?",                        new String[] {address, refNumber, count, seqNumber}, null);                // moveToNext() returns false if no duplicates were found                if (cursor.moveToNext()) {                    loge("Discarding duplicate message segment, refNumber=" + refNumber                            + " seqNumber=" + seqNumber);                    String oldPduString = cursor.getString(PDU_COLUMN);                    byte[] pdu = tracker.getPdu();                    byte[] oldPdu = HexDump.hexStringToByteArray(oldPduString);                    if (!Arrays.equals(oldPdu, tracker.getPdu())) {                        loge("Warning: dup message segment PDU of length " + pdu.length                                + " is different from existing PDU of length " + oldPdu.length);                    }                    return Intents.RESULT_SMS_DUPLICATED;   // reject message                }                cursor.close();            } catch (SQLException e) {                loge("Can't access multipart SMS database", e);                return Intents.RESULT_SMS_GENERIC_ERROR;    // reject message            } finally {                if (cursor != null) {                    cursor.close();                }            }        }        ContentValues values = tracker.getContentValues();        if (VDBG) log("adding content values to raw table: " + values.toString());        Uri newUri = mResolver.insert(sRawUri, values);//保存到raw表        if (DBG) log("URI of new row -> " + newUri);        try {            long rowId = ContentUris.parseId(newUri);            if (tracker.getMessageCount() == 1) {                // set the delete selection args for single-part message                tracker.setDeleteWhere(SELECT_BY_ID, new String[]{Long.toString(rowId)});            }            return Intents.RESULT_SMS_HANDLED;        } catch (Exception e) {            loge("error parsing URI for new row: " + newUri, e);            return Intents.RESULT_SMS_GENERIC_ERROR;        }    }

现在回到上一个方法：

 case Intents.RESULT_SMS_HANDLED:            sendMessage(EVENT_BROADCAST_SMS, tracker);            return Intents.RESULT_SMS_HANDLED;

这里是发出了EVENT_BROADCAST_SMS.

特别注意，刚才我们的状态是DeliveringState。所以，现在我们回到这个状态下看怎么处理这个event:

                case EVENT_BROADCAST_SMS:                    // if any broadcasts were sent, transition to waiting state                    if (processMessagePart((InboundSmsTracker) msg.obj)) {                        transitionTo(mWaitingState);                    }                    return HANDLED;

调用了processMessagePart,同时把状态切为mWaitingState

   boolean processMessagePart(InboundSmsTracker tracker) {        int messageCount = tracker.getMessageCount();        byte[][] pdus;        int destPort = tracker.getDestPort();        if (messageCount == 1) {            // single-part message            pdus = new byte[][]{tracker.getPdu()};        } else {            // multi-part message            Cursor cursor = null;            try {                // used by several query selection arguments                String address = tracker.getAddress();                String refNumber = Integer.toString(tracker.getReferenceNumber());                String count = Integer.toString(tracker.getMessageCount());                // query for all segments and broadcast message if we have all the parts                String[] whereArgs = {address, refNumber, count};                cursor = mResolver.query(sRawUri, PDU_SEQUENCE_PORT_PROJECTION,                        SELECT_BY_REFERENCE, whereArgs, null);                int cursorCount = cursor.getCount();                if (cursorCount < messageCount) {                    // Wait for the other message parts to arrive. It's also possible for the last                    // segment to arrive before processing the EVENT_BROADCAST_SMS for one of the                    // earlier segments. In that case, the broadcast will be sent as soon as all                    // segments are in the table, and any later EVENT_BROADCAST_SMS messages will                    // get a row count of 0 and return.                    return false;                }                // All the parts are in place, deal with them                pdus = new byte[messageCount][];                while (cursor.moveToNext()) {                    // subtract offset to convert sequence to 0-based array index                    int index = cursor.getInt(SEQUENCE_COLUMN) - tracker.getIndexOffset();                    pdus[index] = HexDump.hexStringToByteArray(cursor.getString(PDU_COLUMN));                    // Read the destination port from the first segment (needed for CDMA WAP PDU).                    // It's not a bad idea to prefer the port from the first segment in other cases.                    if (index == 0 && !cursor.isNull(DESTINATION_PORT_COLUMN)) {                        int port = cursor.getInt(DESTINATION_PORT_COLUMN);                        // strip format flags and convert to real port number, or -1                        port = InboundSmsTracker.getRealDestPort(port);                        if (port != -1) {                            destPort = port;                        }                    }                }            } catch (SQLException e) {                loge("Can't access multipart SMS database", e);                return false;            } finally {                if (cursor != null) {                    cursor.close();                }            }        }        BroadcastReceiver resultReceiver = new SmsBroadcastReceiver(tracker);//创建了一个receiver,用于向app广播完后。做扫尾处理。        if (destPort == SmsHeader.PORT_WAP_PUSH) {//判断这个短信是不是wap push.也就是端口短信。我们普通短信都不是wap push            // Build up the data stream            ByteArrayOutputStream output = new ByteArrayOutputStream();            for (byte[] pdu : pdus) {                // 3GPP needs to extract the User Data from the PDU; 3GPP2 has already done this                if (!tracker.is3gpp2()) {                    SmsMessage msg = SmsMessage.createFromPdu(pdu, SmsConstants.FORMAT_3GPP);                    pdu = msg.getUserData();                }                output.write(pdu, 0, pdu.length);            }            int result = mWapPush.dispatchWapPdu(output.toByteArray(), resultReceiver, this);            if (DBG) log("dispatchWapPdu() returned " + result);            // result is Activity.RESULT_OK if an ordered broadcast was sent            return (result == Activity.RESULT_OK);        }        Intent intent;        if (destPort == -1) {            intent = new Intent(Intents.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);            if (componentName != null) {                // Deliver SMS message only to this receiver                intent.setComponent(componentName);                log("Delivering SMS to: " + componentName.getPackageName() +                        " " + componentName.getClassName());            }        } else {            Uri uri = Uri.parse("sms://localhost:" + destPort);            intent = new Intent(Intents.DATA_SMS_RECEIVED_ACTION, uri);        }        intent.putExtra("pdus", pdus);        intent.putExtra("format", tracker.getFormat());        dispatchIntent(intent, android.Manifest.permission.RECEIVE_SMS,                AppOpsManager.OP_RECEIVE_SMS, resultReceiver);//将短信广播出去。注意，在4.4版本里，这里只是广播给系统默认的default sms app.其它sms app是收不到短信的。        return true;    }

这个方法发送的短信广播只是系统默认的default sms app.其它sms app是收不到短信的。那么其它接收短信的app.靠什么收到短信呢。别急，我们刚才有讲过

 BroadcastReceiver resultReceiver = new SmsBroadcastReceiver(tracker);//创建了一个receiver,用于向app广播完后。做扫尾处理。

我们来看一下这个receiver:

 private final class SmsBroadcastReceiver extends BroadcastReceiver {        private final String mDeleteWhere;        private final String[] mDeleteWhereArgs;        private long mBroadcastTimeNano;        SmsBroadcastReceiver(InboundSmsTracker tracker) {            mDeleteWhere = tracker.getDeleteWhere();            mDeleteWhereArgs = tracker.getDeleteWhereArgs();            mBroadcastTimeNano = System.nanoTime();        }        @Override        public void onReceive(Context context, Intent intent) {            String action = intent.getAction();            if (action.equals(Intents.SMS_DELIVER_ACTION)) {                // Now dispatch the notification only intent                intent.setAction(Intents.SMS_RECEIVED_ACTION);                intent.setComponent(null);                dispatchIntent(intent, android.Manifest.permission.RECEIVE_SMS,                        AppOpsManager.OP_RECEIVE_SMS, this);            } else if

这里再次广播了一个intent.只要第三方app去接收这个intent。就能收到短信了。

接下来就是把状态机切回idle状态。这里不再描述。大家往下跟一下代码就清楚了。