APP進程也是從zygote進程孵化出來的，他通過socket與 zygote進行通信虹蓄；
先來看下客戶端的調(diào)用代碼：

客戶端谷朝， 首先是本地通過binder與ActivityManagerService進行通信， 最后調(diào)用到processStart;
ActivityManagerService.java
private final void startProcessLocked(ProcessRecord app, String hostingType){
      startResult = Process.start(entryPoint,
                        app.processName, uid, uid, gids, debugFlags, mountExternal,
                        app.info.targetSdkVersion, app.info.seinfo, requiredAbi, instructionSet,
                        app.info.dataDir, invokeWith, entryPointArgs);
}

->調(diào)用到Process.start,
Process.java
public static final ProcessStartResult start(final String processClass..){
    return zygoteProcess.start(processClass, niceName, uid, gid, gids,..)
}

->zygoteProcess.start
zygoteProcess.java
public final Process.ProcessStartResult start(final String processClass,..){
    return startViaZygote(processClass, niceName, uid, gid, gids);
}
->startViaZygote, sendARGs武花，這里參數(shù)調(diào)用打開 zygoteSocket
private Process.ProcessStartResult startViaZygote(final String processClass,..){
        synchronized(mLock) {
            return zygoteSendArgsAndGetResult(openZygoteSocketIfNeeded(abi), argsForZygote);
        }
}

->openZygoteSocketIfNeeded
private ZygoteState openZygoteSocketIfNeeded(String abi) throws ZygoteStartFailedEx {
    primaryZygoteState = ZygoteState.connect(mSocket);//打開socket連接
}

->zygoteSendArgsAndGetResult
private static Process.ProcessStartResult zygoteSendArgsAndGetResult(){
    //這里就是通過socket發(fā)送命令給Zygote進程
            final BufferedWriter writer = zygoteState.writer;
            final DataInputStream inputStream = zygoteState.inputStream;

            writer.write(Integer.toString(args.size()));
            writer.newLine();

            for (int i = 0; i < sz; i++) {
                String arg = args.get(i);
                writer.write(arg);
                writer.newLine();
            }

            writer.flush();
}

客戶端發(fā)送消息后，下面就是服務器端的接受消息杈帐，這個要從zygote的runloopselect開始

zygoteServer.java
->runSelectLoop
void runSelectLoop(String abiList) throws Zygote.MethodAndArgsCaller {
    ArrayList<ZygoteConnection> peers = new ArrayList<ZygoteConnection>();
    while(true){
        boolean done = peers.get(i).runOnce(this);//執(zhí)行ZygoteConnection的runOnce函數(shù)
    }
}

->runOnce
boolean runOnce(ZygoteServer zygoteServer) throws Zygote.MethodAndArgsCaller {
    //開始fork進程体箕，這個先不跟蹤下去了， 跟systemserver的流程是類似的
    pid = Zygote.forkAndSpecialize(parsedArgs.uid, parsedArgs.gid, parsedArgs.gids,
                    parsedArgs.debugFlags, rlimits, parsedArgs.mountExternal, parsedArgs.seInfo,
                    parsedArgs.niceName, fdsToClose, fdsToIgnore, parsedArgs.instructionSet,
                    parsedArgs.appDataDir);
    
     if (pid == 0) { //創(chuàng)建的子進程
                // in child
                zygoteServer.closeServerSocket();
                IoUtils.closeQuietly(serverPipeFd);
                serverPipeFd = null;
                handleChildProc(parsedArgs, descriptors, childPipeFd, newStderr);

                // should never get here, the child is expected to either
                // throw Zygote.MethodAndArgsCaller or exec().
                return true;
        } else {
                // in parent...pid of < 0 means failure
                IoUtils.closeQuietly(childPipeFd);
                childPipeFd = null;
                return handleParentProc(pid, descriptors, serverPipeFd, parsedArgs);
        }
}
->handleChileProc
private void handleChildProc(Arguments parsedArgs,..){
      //這邊跟systemserver也是非常的類似挑童，這邊根據(jù)傳入的參數(shù)累铅，會反射調(diào)用到進程的主入口ActivityThread.main().
      ZygoteInit.zygoteInit(parsedArgs.targetSdkVersion,
                    parsedArgs.remainingArgs, null /* classLoader */);
}