试着从java到C去理解android中发送短信的源代码
今天在找GPRS的源代码的时候居然找到了SMS的源代码，那么就写个短信发送功能，并来解释下源代码吧（自己的理解，求别喷）。
首先来个短信发送的小程序吧
String number = "110";
String content = "搞死日本人";
SmsManager smsManager = SmsManager.getDefault();
PendingIntent sentIntent = PendingIntent.getBroadcast(MainActivity.this, 0, new Intent(), 0);
//如果字数超过70,需拆分成多条短信发送
if (strContent.length() > 70) {
List<String> msgs = smsManager.divideMessage(content);
for (String msg : msgs) {
smsManager.sendTextMessage(number, null, msg, sentIntent, null);
}
} else {
smsManager.sendTextMessage(number, null, content, sentIntent, null);
}
下面来解释一下这里面用到的两个关键的函数：sendTextMessage 和 divideMessage.
首先来看sendTextMessage：存放于ANDROID.2.3.3/frameworks/base/telephony/java/android/telephony
/**
* Send a text based SMS.
*
* @param destinationAddress the address to send the message to
* @param scAddress is the service center address or null to use
* the current default SMSC
* @param text the body of the message to send
* @param sentIntent if not NULL this <code>PendingIntent</code> is
* broadcast when the message is sucessfully sent, or failed.
* The result code will be <code>Activity.RESULT_OK<code> for success,
* or one of these errors:<br>
* <code>RESULT_ERROR_GENERIC_FAILURE</code><br>
* <code>RESULT_ERROR_RADIO_OFF</code><br>
* <code>RESULT_ERROR_NULL_PDU</code><br>
* For <code>RESULT_ERROR_GENERIC_FAILURE</code> the sentIntent may include
* the extra "errorCode" containing a radio technology specific value,
* generally only useful for troubleshooting.<br>
* The per-application based SMS control checks sentIntent. If sentIntent
* is NULL the caller will be checked against all unknown applications,
* which cause smaller number of SMS to be sent in checking period.
* @param deliveryIntent if not NULL this <code>PendingIntent</code> is
* broadcast when the message is delivered to the recipient. The
* raw pdu of the status report is in the extended data ("pdu").
*
* @throws IllegalArgumentException if destinationAddress or text are empty
*/
public void sendTextMessage(
String destinationAddress, String scAddress, String text,
PendingIntent sentIntent, PendingIntent deliveryIntent) {
if (TextUtils.isEmpty(destinationAddress)) {
throw new IllegalArgumentException("Invalid destinationAddress");
}
if (TextUtils.isEmpty(text)) {
throw new IllegalArgumentException("Invalid message body");
}
try {
ISms iccISms = ISms.Stub.asInterface(ServiceManager.getService("isms"));
if (iccISms != null) {
iccISms.sendText(destinationAddress, scAddress, text, sentIntent, deliveryIntent);
}
} catch (RemoteException ex) {
// ignore it
}
}
这里面最关键的就是
ISms iccISms = ISms.Stub.asInterface(ServiceManager.getService("isms"));
这句话就是获得一个ISms接口的一个实例，然后可以去获得isms服务
找到ISms.aidl(aidl是 Android Interface definition language的缩写，它是一种android内部进程通信接口的描述语言，通过它我们可以定义进程间的通信接口。关于这方面的知识请查看file:///usr/local/dev/android-sdk-linux/docs/guide/developing/tools/aidl.html)，存放于ANDROID.2.3.3/frameworks/base/telephony/java/com/android/internal/telephony/
/** Interface for applications to access the ICC phone book.
*
* <p>The following code snippet demonstrates a static method to
* retrieve the ISms interface from Android:</p>
* <pre>private static ISms getSmsInterface()
throws DeadObjectException {
IServiceManager sm = ServiceManagerNative.getDefault();
ISms ss;
ss = ISms.Stub.asInterface(sm.getService("isms"));
return ss;
}
* </pre>
*/
interface ISms {
/**
* Send an SMS.
*
* @param smsc the SMSC to send the message through, or NULL for the
* default SMSC
* @param text the body of the message to send
* @param sentIntent if not NULL this <code>PendingIntent</code> is
* broadcast when the message is sucessfully sent, or failed.
* The result code will be <code>Activity.RESULT_OK<code> for success,
* or one of these errors:<br>
* <code>RESULT_ERROR_GENERIC_FAILURE</code><br>
* <code>RESULT_ERROR_RADIO_OFF</code><br>
* <code>RESULT_ERROR_NULL_PDU</code><br>
* For <code>RESULT_ERROR_GENERIC_FAILURE</code> the sentIntent may include
* the extra "errorCode" containing a radio technology specific value,
* generally only useful for troubleshooting.<br>
* The per-application based SMS control checks sentIntent. If sentIntent
* is NULL the caller will be checked against all unknown applications,
* which cause smaller number of SMS to be sent in checking period.
* @param deliveryIntent if not NULL this <code>PendingIntent</code> is
* broadcast when the message is delivered to the recipient. The
* raw pdu of the status report is in the extended data ("pdu").
*/ void sendText(in String destAddr, in String scAddr, in String text,
in PendingIntent sentIntent, in PendingIntent deliveryIntent);
}
而sendtext函数就是这个，存放于IccSmsInterfaceManager.java
public void sendText(String destAddr, String scAddr,
String text, PendingIntent sentIntent, PendingIntent deliveryIntent) {
mPhone.getContext().enforceCallingPermission(
"android.permission.SEND_SMS",
"Sending SMS message");
if (Log.isLoggable("SMS", Log.VERBOSE)) {
log("sendText: destAddr=" + destAddr + " scAddr=" + scAddr +
" text='"+ text + "' sentIntent=" +
sentIntent + " deliveryIntent=" + deliveryIntent);
}
mDispatcher.sendText(destAddr, scAddr, text, sentIntent, deliveryIntent);
}
原来调用的是mDispatcher里面的sendText，再去看SMSDispather.java文件
protected abstract void sendText(String destAddr, String scAddr,
String text, PendingIntent sentIntent, PendingIntent deliveryIntent);
擦，一个虚函数，实现在哪？？继续找吧
GsmSMSDispatcher.java
final class GsmSMSDispatcher extends SMSDispatcher {
...
...
...
/** {@inheritDoc} */
protected void sendText(String destAddr, String scAddr, String text,
PendingIntent sentIntent, PendingIntent deliveryIntent) {
SmsMessage.SubmitPdu pdu = SmsMessage.getSubmitPdu(
scAddr, destAddr, text, (deliveryIntent != null));
sendRawPdu(pdu.encodedScAddress, pdu.encodedMessage, sentIntent, deliveryIntent);
}
...
...
}
先看下getSubmitPdu函数吧
/**
* Get an SMS-SUBMIT PDU for a destination address and a message
*
* @param scAddress Service Centre address. Null means use default.
* @return a <code>SubmitPdu</code> containing the encoded SC
* address, if applicable, and the encoded message.
* Returns null on encode error.
*/
public static SubmitPdu getSubmitPdu(String scAddress,
String destinationAddress, String message, boolean statusReportRequested) {
SubmitPduBase spb;
int activePhone = TelephonyManager.getDefault().getPhoneType();
if (PHONE_TYPE_CDMA == activePhone) {
spb = com.android.internal.telephony.cdma.SmsMessage.getSubmitPdu(scAddress,
destinationAddress, message, statusReportRequested, null);
} else {
spb = com.android.internal.telephony.gsm.SmsMessage.getSubmitPdu(scAddress,
destinationAddress, message, statusReportRequested);
}
return new SubmitPdu(spb);
}
再来看下sendRawPdu，注意，现在不是sendText了
protected void sendRawPdu(byte[] smsc, byte[] pdu, PendingIntent sentIntent,
PendingIntent deliveryIntent) {
if (pdu == null) {
if (sentIntent != null) {
try {
sentIntent.send(RESULT_ERROR_NULL_PDU);
} catch (CanceledException ex) {}
}
return;
}
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("smsc", smsc);
map.put("pdu", pdu);
SmsTracker tracker = new SmsTracker(map, sentIntent,
deliveryIntent);
int ss = mPhone.getServiceState().getState();
if (ss != ServiceState.STATE_IN_SERVICE) {
handleNotInService(ss, tracker);
} else {
String appName = getAppNameByIntent(sentIntent);
if (mCounter.check(appName, SINGLE_PART_SMS)) {
sendSms(tracker);
} else {
sendMessage(obtainMessage(EVENT_POST_ALERT, tracker));
}
}
}
关键是那个sendSms函数，然后在SMSDispathcer里面找到sendSms也是一个虚函数，然后在GsmSMSDispatcher.java里面找到实现
protected void sendSms(SmsTracker tracker) {
HashMap map = tracker.mData;
byte smsc[] = (byte[]) map.get("smsc");
byte pdu[] = (byte[]) map.get("pdu");
Message reply = obtainMessage(EVENT_SEND_SMS_COMPLETE, tracker);
mCm.sendSMS(IccUtils.bytesToHexString(smsc),
IccUtils.bytesToHexString(pdu), reply);
}
mCm是什么呢？
protected CommandsInterface mCm; 接口再次出现！这个接口与RIL.java相关，于是看一看RIL.java文件，存放于ANDROID.2.3.3/frameworks/base/telephony/java/com/android/internal/telephony/
sendSMS (String smscPDU, String pdu, Message result) {
RILRequest rr
= RILRequest.obtain(RIL_REQUEST_SEND_SMS, result);
rr.mp.writeInt(2);
rr.mp.writeString(smscPDU);
rr.mp.writeString(pdu);
if (RILJ_LOGD) riljLog(rr.serialString() + "> " + requestToString(rr.mRequest));
send(rr);
}
同样在RIL.java文件安中找到 send（RILRequest rr）
private void
send(RILRequest rr) {
Message msg;
msg = mSender.obtainMessage(EVENT_SEND, rr);
acquireWakeLock();
msg.sendToTarget();
}
再根据handle，同样在RIL.java中找到
class RILSender extends Handler implements Runnable {
public RILSender(Looper looper) {
super(looper);
}
// Only allocated once
byte[] dataLength = new byte[4];
//***** Runnable implementation
public void
run() {
//setup if needed
}
//***** Handler implemementation
public void
handleMessage(Message msg) {
RILRequest rr = (RILRequest)(msg.obj);
RILRequest req = null;
switch (msg.what) {
case EVENT_SEND:
/**
* mRequestMessagePending++ already happened for every
* EVENT_SEND, thus we must make sure
* mRequestMessagePending-- happens once and only once
*/
boolean alreadySubtracted = false;
try {
LocalSocket s;
s = mSocket;
if (s == null) {
rr.onError(RADIO_NOT_AVAILABLE, null);
rr.release();
if (mRequestMessagesPending > 0)
mRequestMessagesPending--;
alreadySubtracted = true;
return;
}
synchronized (mRequestsList) {
mRequestsList.add(rr);
mRequestMessagesWaiting++;
}
if (mRequestMessagesPending > 0)
mRequestMessagesPending--;
alreadySubtracted = true;
byte[] data;
data = rr.mp.marshall();
rr.mp.recycle();
rr.mp = null;
if (data.length > RIL_MAX_COMMAND_BYTES) {
throw new RuntimeException(
"Parcel larger than max bytes allowed! "
+ data.length);
}
// parcel length in big endian
dataLength[0] = dataLength[1] = 0;
dataLength[2] = (byte)((data.length >> 8) & 0xff);
dataLength[3] = (byte)((data.length) & 0xff);
//Log.v(LOG_TAG, "writing packet: " + data.length + " bytes");
s.getOutputStream().write(dataLength);
s.getOutputStream().write(data);
} catch (IOException ex) {
Log.e(LOG_TAG, "IOException", ex);
req = findAndRemoveRequestFromList(rr.mSerial);
// make sure this request has not already been handled,
// eg, if RILReceiver cleared the list.
if (req != null || !alreadySubtracted) {
rr.onError(RADIO_NOT_AVAILABLE, null);
rr.release();
}
} catch (RuntimeException exc) {
Log.e(LOG_TAG, "Uncaught exception ", exc);
req = findAndRemoveRequestFromList(rr.mSerial);
// make sure this request has not already been handled,
// eg, if RILReceiver cleared the list.
if (req != null || !alreadySubtracted) {
rr.onError(GENERIC_FAILURE, null);
rr.release();
}
}
if (!alreadySubtracted && mRequestMessagesPending > 0) {
mRequestMessagesPending--;
}
break;
关键代码：
|
s.getOutputStream().write(dataLength);
s.getOutputStream().write(data);
这样就通过socket把内容发出,LocalSocket.java存放于frameworks/base/core/java/android/net
LocalSocketImpl impl;
public LocalSocket() {
this(new LocalSocketImpl());
isBound = false;
isConnected = false;
}
/**
* Retrieves the output stream for this instance.
*
* @return output stream
* @throws IOException if socket has been closed or cannot be created.
*/
public OutputStream getOutputStream() throws IOException {
implCreateIfNeeded();
return impl.getOutputStream();
}
/**
* It's difficult to discern from the spec when impl.create() should be
* called, but it seems like a reasonable rule is "as soon as possible,
* but not in a context where IOException cannot be thrown"
*
* @throws IOException from SocketImpl.create()
*/
private void implCreateIfNeeded() throws IOException {
if (!implCreated) {
synchronized (this) {
if (!implCreated) {
try {
impl.create(true);
} finally {
implCreated = true;
}
}
}
}
}
LocalSocketImpl.jva同样存放于net文件夹
关键的部分要到来了
/** {@inheritDoc} */
@Override
public void write (byte[] b, int off, int len) throws IOException {
synchronized (writeMonitor) {
FileDescriptor myFd = fd;
if (myFd == null) throw new IOException("socket closed");
if (off < 0 || len < 0 || (off + len) > b.length ) {
throw new ArrayIndexOutOfBoundsException();
}
writeba_native(b, off, len, myFd);
}
}
看见没？
writeba_native(b, off, len, myFd);
在base/core/jni/android_net_LocalSocketImpl.cpp
JNI中发现调用的就是{"writeba_native", "([BIILjava/io/FileDescriptor;)V", (void*) socket_writeba},而socket_writeba就是调用的下面这个函数：
static int socket_write_all(JNIEnv *env, jobject object, int fd,
void *buf, size_t len)
{
ssize_t ret;
struct msghdr msg;
unsigned char *buffer = (unsigned char *)buf;
memset(&msg, 0, sizeof(msg));
jobjectArray outboundFds
= (jobjectArray)env->GetObjectField(
object, field_outboundFileDescriptors);
if (env->ExceptionOccurred() != NULL) {
return -1;
}
struct cmsghdr *cmsg;
int countFds = outboundFds == NULL ? 0 : env->GetArrayLength(outboundFds);
int fds[countFds];
char msgbuf[CMSG_SPACE(countFds)];
// Add any pending outbound file descriptors to the message
if (outboundFds != NULL) {
if (env->ExceptionOccurred() != NULL) {
return -1;
}
for (int i = 0; i < countFds; i++) {
jobject fdObject = env->GetObjectArrayElement(outboundFds, i);
if (env->ExceptionOccurred() != NULL) {
return -1;
}
fds[i] = jniGetFDFromFileDescriptor(env, fdObject);
if (env->ExceptionOccurred() != NULL) {
return -1;
}
}
// See "man cmsg" really
msg.msg_control = msgbuf;
msg.msg_controllen = sizeof msgbuf;
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof fds);
memcpy(CMSG_DATA(cmsg), fds, sizeof fds);
}
// We only write our msg_control during the first write
while (len > 0) {
struct iovec iv;
memset(&iv, 0, sizeof(iv));
iv.iov_base = buffer;
iv.iov_len = len;
msg.msg_iov = &iv;
msg.msg_iovlen = 1;
do {
ret = sendmsg(fd, &msg, MSG_NOSIGNAL);
} while (ret < 0 && errno == EINTR);
if (ret < 0) {
jniThrowIOException(env, errno);
return -1;
}
buffer += ret;
len -= ret;
// Wipes out any msg_control too
memset(&msg, 0, sizeof(msg));
}
return 0;
}
终于找到了，原来就是linux下的ssize_t sendmsg这个系统调用！！！！！
再来看divideMessage
/**
* Divide a message text into several fragments, none bigger than
* the maximum SMS message size.
*
* @param text the original message. Must not be null.
* @return an <code>ArrayList</code> of strings that, in order,
* comprise the original message
*/
public ArrayList<String> divideMessage(String text) {
return SmsMessage.fragmentText(text);
}
而这个函数就主要调用里fragmentText这个方法
/**
* Divide a message text into several fragments, none bigger than
* the maximum SMS message text size.
*
* @param text text, must not be null.
* @return an <code>ArrayList</code> of strings that, in order,
* comprise the original msg text
*
* @hide
*/
public static ArrayList<String> fragmentText(String text) {
int activePhone = TelephonyManager.getDefault().getPhoneType();
TextEncodingDetails ted = (PHONE_TYPE_CDMA == activePhone) ?
com.android.internal.telephony.cdma.SmsMessage.calculateLength(text, false) :
com.android.internal.telephony.gsm.SmsMessage.calculateLength(text, false);
// TODO(cleanup): The code here could be rolled into the logic
// below cleanly if these MAX_* constants were defined more
// flexibly...
int limit;
if (ted.msgCount > 1) {
limit = (ted.codeUnitSize == ENCODING_7BIT) ?
MAX_USER_DATA_SEPTETS_WITH_HEADER : MAX_USER_DATA_BYTES_WITH_HEADER;
} else {
limit = (ted.codeUnitSize == ENCODING_7BIT) ?
MAX_USER_DATA_SEPTETS : MAX_USER_DATA_BYTES;
}
int pos = 0; // Index in code units.
int textLen = text.length();
ArrayList<String> result = new ArrayList<String>(ted.msgCount);
while (pos < textLen) {
int nextPos = 0; // Counts code units.
if (ted.codeUnitSize == ENCODING_7BIT) {
if (activePhone == PHONE_TYPE_CDMA && ted.msgCount == 1) {
// For a singleton CDMA message, the encoding must be ASCII...
nextPos = pos + Math.min(limit, textLen - pos);
} else {
// For multi-segment messages, CDMA 7bit equals GSM 7bit encoding (EMS mode).
nextPos = GsmAlphabet.findGsmSeptetLimitIndex(text, pos, limit);
}
} else { // Assume unicode.
nextPos = pos + Math.min(limit / 2, textLen - pos);
}
if ((nextPos <= pos) || (nextPos > textLen)) {
Log.e(LOG_TAG, "fragmentText failed (" + pos + " >= " + nextPos + " or " +
nextPos + " >= " + textLen + ")");
break;
}
result.add(text.substring(pos, nextPos));
pos = nextPos;
}
return result;
}
其实我觉得发送短信这个功能最重要的还是去学习下关于aidl方面的知识，进程间通信很重要，尤其是我们这些刚接触android不久的经验少的孩子。自己的理解很狭隘，能力也有限，只是做个抛砖引玉的效果，希望大家一起来分享自己的心得。