《转》深入理解Activity启动流程(三)–Activity启动的详细流程1

//ActivityManagerService类
final ProcessRecord startProcessLocked(String processName,
ApplicationInfo info, boolean knownToBeDead, int intentFlags,
String hostingType, ComponentName hostingName, boolean allowWhileBooting,
boolean isolated) {
ProcessRecord app;
if (!isolated) {
app = getProcessRecordLocked(processName, info.uid);
} else {
//...
}
//...
if (app == null) {
app = newProcessRecordLocked(null, info, processName, isolated);
if (app == null) {
Slog.w(TAG, "Failed making new process record for "
+ processName + "/" + info.uid + " isolated=" + isolated);
return null;
}
mProcessNames.put(processName, app.uid, app);
if (isolated) {
mIsolatedProcesses.put(app.uid, app);
}
} else {
//..
}
//...
startProcessLocked(app, hostingType, hostingNameStr);
//...
}

//ActivityManagerService类
private final void startProcessLocked(ProcessRecord app,
String hostingType, String hostingNameStr) {
//...
try {
//...
// Start the process. It will either succeed and return a result containing
// the PID of the new process, or else throw a RuntimeException.
//Zygote孵化dalvik应用进程后，会执行android.app.ActivityThread类的main方法
Process.ProcessStartResult startResult = Process.start("android.app.ActivityThread",
app.processName, uid, uid, gids, debugFlags, mountExternal,
app.info.targetSdkVersion, app.info.seinfo, null);
//...
} catch (RuntimeException e) {
//...
}
}

//Process类
public static final ProcessStartResult start(final String processClass,
final String niceName,
int uid, int gid, int[] gids,
int debugFlags, int mountExternal,
int targetSdkVersion,
String seInfo,
String[] zygoteArgs) {
try{
startViaZygote(processClass, niceName, uid, gid, gids,
debugFlags, mountExternal, targetSdkVersion, seInfo, zygoteArgs);
}catch (ZygoteStartFailedEx ex) {
//...
}
}

//ZygoteInit类
private static void runSelectLoopMode() throws MethodAndArgsCaller {
//...
while (true) {
//...
try {
fdArray = fds.toArray(fdArray);
index = selectReadable(fdArray);
} catch (IOException ex) {
throw new RuntimeException("Error in select()", ex);
}
if (index < 0) {
throw new RuntimeException("Error in select()");
} else if (index == 0) {
//监听客户连接请求
ZygoteConnection newPeer = acceptCommandPeer();
peers.add(newPeer);
fds.add(newPeer.getFileDesciptor());
} else {
//若客户发送孵化进程的请求过来，
//此时便需要调用ZygoteConnection的runOnce方法孵化进程
boolean done;
done = peers.get(index).runOnce();
if (done) {
peers.remove(index);
fds.remove(index);
}
}
}
}

//ZygoteConnection类
boolean runOnce() throws ZygoteInit.MethodAndArgsCaller {
//...
try {
//...
pid = Zygote.forkAndSpecialize(parsedArgs.uid, parsedArgs.gid, parsedArgs.gids,
parsedArgs.debugFlags, rlimits, parsedArgs.mountExternal, parsedArgs.seInfo,
parsedArgs.niceName);
}
//...
try {
if (pid == 0) {
// in child
IoUtils.closeQuietly(serverPipeFd);
serverPipeFd = null;
//handleChildProc是一个很重要的函数，在该函数里使用了异常进行逃逸
handleChildProc(parsedArgs, descriptors, childPipeFd, newStderr);
//...
} else {
//...
}
} finally {
//...
}
}

//ZygoteConnection类
private void handleChildProc(Arguments parsedArgs,
FileDescriptor[] descriptors, FileDescriptor pipeFd, PrintStream newStderr)
throws ZygoteInit.MethodAndArgsCaller {
//...
if (parsedArgs.runtimeInit) {
//...
} else {
String className;
try {
//这里得到的classname实际是android.app.ActivityThread
className = parsedArgs.remainingArgs[0];
} catch (ArrayIndexOutOfBoundsException ex) {
logAndPrintError(newStderr,
"Missing required class name argument", null);
return;
}
//...
if (parsedArgs.invokeWith != null) {
//...
} else {
ClassLoader cloader;
if (parsedArgs.classpath != null) {
cloader = new PathClassLoader(parsedArgs.classpath,
ClassLoader.getSystemClassLoader());
} else {
cloader = ClassLoader.getSystemClassLoader();
}
//调用ZygoteInit.invokeStaticMain执行android.app.ActivityThread的main方法
try {
ZygoteInit.invokeStaticMain(cloader, className, mainArgs);
} catch (RuntimeException ex) {
logAndPrintError(newStderr, "Error starting.", ex);
}
}
}
}

//ZygoteInit类
static void invokeStaticMain(ClassLoader loader,
String className, String[] argv)
throws ZygoteInit.MethodAndArgsCaller {
//...
Method m;
try {
m = cl.getMethod("main", new Class[] { String[].class });
} catch(//...){
}
//...
throw new ZygoteInit.MethodAndArgsCaller(m, argv);
}

public static class MethodAndArgsCaller extends Exception
implements Runnable {
//...
public void run() {
try {
mMethod.invoke(null, new Object[] { mArgs });
}//...
}
}

//ZygoteInit类
public static void main(String argv[]) {
try {
//...
} catch (MethodAndArgsCaller caller) {
caller.run();
} catch (RuntimeException ex) {
//...
}
}