void startSpecificActivity(ActivityRecord r, boolean andResume, boolean checkConfig) {
    // Is this activity's application already running?
    final WindowProcessController wpc =
            mService.getProcessController(r.processName, r.info.applicationInfo.uid);
    boolean knownToBeDead = false;
    if (wpc != null && wpc.hasThread()) {
        realStartActivityLocked(r, wpc, andResume, checkConfig);
        return;
        ...
        knownToBeDead = true;
    }
    r.notifyUnknownVisibilityLaunchedForKeyguardTransition();
    final boolean isTop = andResume && r.isTopRunningActivity();
    mService.startProcessAsync(r, knownToBeDead, isTop, isTop ? "top-activity" : "activity");
}

void startProcessAsync(ActivityRecord activity, boolean knownToBeDead, boolean isTop,
        String hostingType) {
    final Message m = PooledLambda.obtainMessage(ActivityManagerInternal::startProcess,
            mAmInternal, activity.processName, activity.info.applicationInfo, knownToBeDead,
            isTop, hostingType, activity.intent.getComponent());
    mH.sendMessage(m);
}

public final class LocalService extends ActivityManagerInternal

@Override
public void startProcess(String processName, ApplicationInfo info, boolean knownToBeDead,
        boolean isTop, String hostingType, ComponentName hostingName) {
    startProcessLocked(processName, info, knownToBeDead, 0 /* intentFlags */,
            new HostingRecord(hostingType, hostingName, isTop),
            ZYGOTE_POLICY_FLAG_LATENCY_SENSITIVE, false /* allowWhileBooting */,
            false /* isolated */, true /* keepIfLarge */);  
}

final ProcessRecord startProcessLocked(String processName,
        ApplicationInfo info, boolean knownToBeDead, int intentFlags,
        HostingRecord hostingRecord, int zygotePolicyFlags, boolean allowWhileBooting,
        boolean isolated, boolean keepIfLarge) {
    return mProcessList.startProcessLocked(processName, info, knownToBeDead, intentFlags,
            hostingRecord, zygotePolicyFlags, allowWhileBooting, isolated, 0 /* isolatedUid */,
            keepIfLarge, null /* ABI override */, null /* entryPoint */,
            null /* entryPointArgs */, null /* crashHandler */);
}

    final ProcessRecord startProcessLocked(String processName, ApplicationInfo info,
            boolean knownToBeDead, int intentFlags, HostingRecord hostingRecord,
            int zygotePolicyFlags, boolean allowWhileBooting, boolean isolated, int isolatedUid,
            boolean keepIfLarge, String abiOverride, String entryPoint, String[] entryPointArgs,
            Runnable crashHandler) {
        long startTime = SystemClock.uptimeMillis();
        ProcessRecord app;
		//isolated傳遞進(jìn)來(lái)是false，
        if (!isolated) {
			//從mProcessNames緩存獲取，由于是首次創(chuàng)建，null
            app = getProcessRecordLocked(processName, info.uid, keepIfLarge);
            checkSlow(startTime, "startProcess: after getProcessRecord");
			//判斷要啟動(dòng)進(jìn)程是否后臺(tái)運(yùn)行，直接return null
            if ((intentFlags & Intent.FLAG_FROM_BACKGROUND) != 0) {
                if (mService.mAppErrors.isBadProcessLocked(info)) {
                    return null;
                }
            } else {
                //重置進(jìn)程的crash狀態(tài),使其處于正常狀態(tài)
                mService.mAppErrors.resetProcessCrashTimeLocked(info);
                if (mService.mAppErrors.isBadProcessLocked(info)) {
                    mService.mAppErrors.clearBadProcessLocked(info);
                    if (app != null) {
                        app.bad = false;
                    }
                }
            }
        } else {
            app = null;
        }
        ProcessRecord precedence = null;
        if (app != null && app.pid > 0) {
            if ((!knownToBeDead && !app.killed) || app.thread == null) {
                app.addPackage(info.packageName, info.longVersionCode, mService.mProcessStats);
                return app;
            }
            ProcessList.killProcessGroup(app.uid, app.pid);
            precedence = app;
            app = null;
        }
        if (app == null) {
			// 分析一、創(chuàng)建新的應(yīng)用進(jìn)程描述ProcessRocrd
			//內(nèi)部會(huì)將自己添加到mProcessNames中
			app = newProcessRecordLocked(info, processName, isolated, isolatedUid, hostingRecord);
			if (app == null) {
                return null;
            }
			//此時(shí)三者都是null
            app.crashHandler = crashHandler;
            app.isolatedEntryPoint = entryPoint;
            app.isolatedEntryPointArgs = entryPointArgs;
            if (precedence != null) {
                app.mPrecedence = precedence;
                precedence.mSuccessor = app;
            }
        } else {
            app.addPackage(info.packageName, info.longVersionCode, mService.mProcessStats);
        }
        // If the system is not ready yet, then hold off on starting this
        // process until it is.
        if (!mService.mProcessesReady
                && !mService.isAllowedWhileBooting(info)
                && !allowWhileBooting) {
            if (!mService.mProcessesOnHold.contains(app)) {
                mService.mProcessesOnHold.add(app);
            }
            if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES,
                    "System not ready, putting on hold: " + app);
            checkSlow(startTime, "startProcess: returning with proc on hold");
            return app;
        }
		分析二：
        final boolean success =
                startProcessLocked(app, hostingRecord, zygotePolicyFlags, abiOverride);
        checkSlow(startTime, "startProcess: done starting proc!");
        return success ? app : null;
    }

final boolean startProcessLocked(ProcessRecord app, HostingRecord hostingRecord,
        int zygotePolicyFlags, String abiOverride) {
    return startProcessLocked(app, hostingRecord, zygotePolicyFlags,
            false /* disableHiddenApiChecks */, false /* disableTestApiChecks */,
            false /* mountExtStorageFull */, abiOverride);
}

    boolean startProcessLocked(ProcessRecord app, HostingRecord hostingRecord,
            int zygotePolicyFlags, boolean disableHiddenApiChecks, boolean disableTestApiChecks,
            boolean mountExtStorageFull, String abiOverride) {
			...
            app.gids = gids;
            app.setRequiredAbi(requiredAbi);
            app.instructionSet = instructionSet;
            final String seInfo = app.info.seInfo
                    + (TextUtils.isEmpty(app.info.seInfoUser) ? "" : app.info.seInfoUser);
            //分析一：確定要啟動(dòng)應(yīng)用程序的類名
            final String entryPoint = "android.app.ActivityThread";
			//分析二：調(diào)用另外一個(gè)重載函數(shù)
            return startProcessLocked(hostingRecord, entryPoint, app, uid, gids,
                    runtimeFlags, zygotePolicyFlags, mountExternal, seInfo, requiredAbi,
                    instructionSet, invokeWith, startTime);
        } catch (RuntimeException e) {
		  	...
        }
    }

 boolean startProcessLocked(HostingRecord hostingRecord, String entryPoint, ProcessRecord app,
            int uid, int[] gids, int runtimeFlags, int zygotePolicyFlags, int mountExternal,
            String seInfo, String requiredAbi, String instructionSet, String invokeWith,
            long startTime) {
            ...
            final Process.ProcessStartResult startResult = startProcess(hostingRecord,
                    entryPoint, app,
                    uid, gids, runtimeFlags, zygotePolicyFlags, mountExternal, seInfo,
                    requiredAbi, instructionSet, invokeWith, startTime);
            handleProcessStartedLocked(app, startResult.pid, startResult.usingWrapper,
                    startSeq, false);
           ...
        }
    }

Process.start=>ZygoteProcess.start=>ZygoteState.start=>ZygoteState.startViaZygote

private Process.ProcessStartResult startViaZygote(...)
                                                  throws ZygoteStartFailedEx {
        //根據(jù)傳遞進(jìn)來(lái)的參數(shù)，拼接成字符串并收集到ArrayList<String>類型argsForZygote
        //將作為新應(yīng)用程序的主函數(shù)的參數(shù)
        return zygoteSendArgsAndGetResult(openZygoteSocketIfNeeded(abi),
                                          zygotePolicyFlags,
                                          argsForZygote);
}

private ZygoteState openZygoteSocketIfNeeded(String abi) throws ZygoteStartFailedEx {
    try {
    	//建立和Zygote的Socket連接
        attemptConnectionToPrimaryZygote();
		//匹配abi的架構(gòu)。在Zygote的創(chuàng)建對(duì)應(yīng)四種模式:32,32_64和64，64_32
		//32,64
        if (primaryZygoteState.matches(abi)) {
            return primaryZygoteState;
        }
		//主要架構(gòu)模式不配，匹配第二種 32_64,64_32
        if (mZygoteSecondarySocketAddress != null) {
            // The primary zygote didn't match. Try the secondary.
            attemptConnectionToSecondaryZygote();
            if (secondaryZygoteState.matches(abi)) {
                return secondaryZygoteState;
            }
        }
    } catch (IOException ioe) {
        throw new ZygoteStartFailedEx("Error connecting to zygote", ioe);
    }
    throw new ZygoteStartFailedEx("Unsupported zygote ABI: " + abi);
}

private void attemptConnectionToPrimaryZygote() throws IOException {
    if (primaryZygoteState == null || primaryZygoteState.isClosed()) {
        primaryZygoteState =
                ZygoteState.connect(mZygoteSocketAddress, mUsapPoolSocketAddress);
        maybeSetApiBlacklistExemptions(primaryZygoteState, false);
        maybeSetHiddenApiAccessLogSampleRate(primaryZygoteState);
    }
}

zygoteSendArgsAndGetResult=>attemptZygoteSendArgsAndGetResult

    private Process.ProcessStartResult attemptZygoteSendArgsAndGetResult(
            ZygoteState zygoteState, String msgStr) throws ZygoteStartFailedEx {
        try {
            final BufferedWriter zygoteWriter = zygoteState.mZygoteOutputWriter;
            final DataInputStream zygoteInputStream = zygoteState.mZygoteInputStream;
            zygoteWriter.write(msgStr);
            zygoteWriter.flush();
            Process.ProcessStartResult result = new Process.ProcessStartResult();
            result.pid = zygoteInputStream.readInt();
            result.usingWrapper = zygoteInputStream.readBoolean();
            if (result.pid < 0) {
                throw new ZygoteStartFailedEx("fork() failed");
            }
            return result;
        } catch (IOException ex) {
            zygoteState.close();
            Log.e(LOG_TAG, "IO Exception while communicating with Zygote - "
                    + ex.toString());
            throw new ZygoteStartFailedEx(ex);
        }
    }

    public static void main(String argv[]) {
        ZygoteServer zygoteServer = null;
        Runnable caller;
        try {
        	...
            boolean startSystemServer = false;
            String zygoteSocketName = "zygote";
            String abiList = null;
            boolean enableLazyPreload = false;
            for (int i = 1; i < argv.length; i++) {
                if ("start-system-server".equals(argv[i])) {
                    startSystemServer = true; //判斷是否SystemServer進(jìn)程
                } else if ("--enable-lazy-preload".equals(argv[i])) {
                    enableLazyPreload = true;
                } else if (argv[i].startsWith(ABI_LIST_ARG)) {
                    abiList = argv[i].substring(ABI_LIST_ARG.length());
                } else if (argv[i].startsWith(SOCKET_NAME_ARG)) {
                	//SCOKET_NAME_ARG="--socket-name=",根據(jù)參數(shù)得到SocketName
                    zygoteSocketName = argv[i].substring(SOCKET_NAME_ARG.length());
                } else {
                    throw new RuntimeException("Unknown command line argument: " + argv[i]);
                }
            }
		    //PRIMARY_SOCKET_NAME=zygote
            final boolean isPrimaryZygote = zygoteSocketName.equals(Zygote.PRIMARY_SOCKET_NAME);
         	gcAndFinalize();
            Zygote.initNativeState(isPrimaryZygote);
            ZygoteHooks.stopZygoteNoThreadCreation();
            zygoteServer = new ZygoteServer(isPrimaryZygote);
            if (startSystemServer) {
            	//啟動(dòng)SystemServer進(jìn)程
                Runnable r = forkSystemServer(abiList, zygoteSocketName, zygoteServer);
                if (r != null) {
                    r.run();
                    return;
                }
            }
		   //循環(huán)等待AMS來(lái)請(qǐng)求創(chuàng)建新的進(jìn)程
            caller = zygoteServer.runSelectLoop(abiList);
        } catch (Throwable ex) {
            Log.e(TAG, "System zygote died with exception", ex);
            throw ex;
        } finally {
            if (zygoteServer != null) {
                zygoteServer.closeServerSocket();
            }
        }
		//調(diào)用新的進(jìn)程主函數(shù)
        if (caller != null) {
            caller.run();
        }
    }

 /**
     * Runs the zygote process's select loop. Accepts new connections as
     * they happen, and reads commands from connections one spawn-request's
     * worth at a time.
     */
    Runnable runSelectLoop(String abiList) {
        while (true) {
         	...
            ZygoteConnection connection = peers.get(pollIndex);
            final Runnable command = connection.processOneCommand(this);
			...
            if (mIsForkChild) {
                return command;
            }
            ....       
   		}
	}

Runnable processOneCommand(ZygoteServer zygoteServer) {
    ...
    args = Zygote.readArgumentList(mSocketReader);
    //根據(jù)參數(shù)內(nèi)容，作其他類型的處理
    ...
    //創(chuàng)建進(jìn)程,調(diào)用底層nativeForkAndSpecialize方法，通過(guò)fork當(dāng)前進(jìn)程來(lái)創(chuàng)建一個(gè)子線程。
    pid = Zygote.forkAndSpecialize(parsedArgs.mUid, parsedArgs.mGid, parsedArgs.mGids,
            parsedArgs.mRuntimeFlags, rlimits, parsedArgs.mMountExternal, parsedArgs.mSeInfo,
            parsedArgs.mNiceName, fdsToClose, fdsToIgnore, parsedArgs.mStartChildZygote,
            parsedArgs.mInstructionSet, parsedArgs.mAppDataDir, parsedArgs.mIsTopApp,
            parsedArgs.mPkgDataInfoList, parsedArgs.mWhitelistedDataInfoList,
            parsedArgs.mBindMountAppDataDirs, parsedArgs.mBindMountAppStorageDirs);
    ...
    if (pid == 0) {
        //設(shè)置mIsForkChild=true
        zygoteServer.setForkChild();
       //關(guān)閉Socket連接
        zygoteServer.closeServerSocket();
        IoUtils.closeQuietly(serverPipeFd);
        serverPipeFd = null;
       //執(zhí)行子進(jìn)程內(nèi)容
        return handleChildProc(parsedArgs, childPipeFd, parsedArgs.mStartChildZygote);
    } 
    ...
}

private Runnable handleChildProc(ZygoteArguments parsedArgs,
        FileDescriptor pipeFd, boolean isZygote) {
        ...
        if (!isZygote) {
            return ZygoteInit.zygoteInit(parsedArgs.mTargetSdkVersion,
                    parsedArgs.mDisabledCompatChanges,
                    parsedArgs.mRemainingArgs, null /* classLoader */);
        } else {
            return ZygoteInit.childZygoteInit(parsedArgs.mTargetSdkVersion,
                    parsedArgs.mRemainingArgs, null /* classLoader */);
        }
}

public static final Runnable zygoteInit(int targetSdkVersion, long[] disabledCompatChanges,
        String[] argv, ClassLoader classLoader) {
    RuntimeInit.commonInit();
    ZygoteInit.nativeZygoteInit();//為新進(jìn)程創(chuàng)建Binder線程池
    return RuntimeInit.applicationInit(targetSdkVersion, disabledCompatChanges, argv,
            classLoader);
}

    protected static Runnable applicationInit(int targetSdkVersion, long[] disabledCompatChanges,
            String[] argv, ClassLoader classLoader) {
        final Arguments args = new Arguments(argv); 
        return findStaticMain(args.startClass, args.startArgs, classLoader);
    }

protected static Runnable findStaticMain(String className, String[] argv,
        ClassLoader classLoader) {
    ...
    Class<?> cl = Class.forName(className, true, classLoader);
    Method m = cl.getMethod("main", new Class[] { String[].class });
    ...
    return new MethodAndArgsCaller(m, argv);
}

static class MethodAndArgsCaller implements Runnable {
    /** method to call */
    private final Method mMethod;
    /** argument array */
    private final String[] mArgs;
    public MethodAndArgsCaller(Method method, String[] args) {
        mMethod = method;
        mArgs = args;
    }
    public void run() {
        ...
        mMethod.invoke(null, new Object[] { mArgs });
        ...
    }
}

public static void main(String[] args) {
    Looper.prepareMainLooper();
    ActivityThread thread = new ActivityThread();
    thread.attach(false, startSeq);
    if (sMainThreadHandler == null) {
        sMainThreadHandler = thread.getHandler();
    }
    Looper.loop();
}