ActivityManagerService和launcher的启动

SystemServer第三个启动的是ActivityManagerService

本文参考http://blog.csdn.net/lilian0118/article/details/26561835

（frameworks/base/services/java/com/android/server/SystemServer.java）

@Overridepublic void run() {….Slog.i(TAG, "Activity Manager");            context = ActivityManagerService.main(factoryTest);….ActivityManagerService.setSystemProcess();…..Slog.i(TAG, "System Content Providers");            ActivityManagerService.installSystemProviders();….ActivityManagerService.self().setWindowManager(wm); ActivityManagerService.self().systemReady(new Runnable() {            public void run() {                Slog.i(TAG, "Making services ready");                try {                    ActivityManagerService.self().startObservingNativeCrashes(); // 开始监视native是否crash                } catch (Throwable e) {                    reportWtf("observing native crashes", e);                }                if (!headless) startSystemUi(contextF);                try {                    if (mountServiceF != null) mountServiceF.systemReady();                } catch (Throwable e) {                    reportWtf("making Mount Service ready", e);                }...}};}

可以看出ActivityManagerService还跟SystemProvider和WindowManager有关系

先看

context = ActivityManagerService.main(factoryTest);

public static final Context main(int factoryTest) {        AThread thr = new AThread();        thr.start();        synchronized (thr) {            while (thr.mService == null) {                try {                    thr.wait();                } catch (InterruptedException e) {                }            }        }        ActivityManagerService m = thr.mService;        mSelf = m;        ActivityThread at = ActivityThread.systemMain();        mSystemThread = at;        Context context = at.getSystemContext();        context.setTheme(android.R.style.Theme_Holo);        m.mContext = context;        m.mFactoryTest = factoryTest;        m.mMainStack = new ActivityStack(m, context, true, thr.mLooper);        m.mIntentFirewall = new IntentFirewall(m.new IntentFirewallInterface());        m.mBatteryStatsService.publish(context);        m.mUsageStatsService.publish(context);        m.mAppOpsService.publish(context);        synchronized (thr) {            thr.mReady = true;            thr.notifyAll();        }        m.startRunning(null, null, null, null);                return context;    }

我们一行一行代码来分析

AThread thr = new AThread();        thr.start();        synchronized (thr) {            while (thr.mService == null) {                try {                    thr.wait();                } catch (InterruptedException e) {                }            }        }        ActivityManagerService m = thr.mService;        mSelf = m;

首先创建了AThread对象，然后等待Athread创建thr.mService成功，如果创建不成功就一直等待

static class AThread extends Thread {        ActivityManagerService mService;        Looper mLooper;        boolean mReady = false;        public AThread() {            super("ActivityManager");        }        public void run() {            Looper.prepare();            android.os.Process.setThreadPriority(                    android.os.Process.THREAD_PRIORITY_FOREGROUND);            android.os.Process.setCanSelfBackground(false);            ActivityManagerService m = new ActivityManagerService();            synchronized (this) {                mService = m;                mLooper = Looper.myLooper();                notifyAll();            }            synchronized (this) {                while (!mReady) {                    try {                        wait();                    } catch (InterruptedException e) {                    }                }            }            // For debug builds, log event loop stalls to dropbox for analysis.            if (StrictMode.conditionallyEnableDebugLogging()) {                Slog.i(TAG, "Enabled StrictMode logging for AThread's Looper");            }            Looper.loop();        }    }

在Athread里面创建一个ActivityManagerService对象

private ActivityManagerService() {        Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass());                mFgBroadcastQueue = new BroadcastQueue(this, "foreground", BROADCAST_FG_TIMEOUT); // 创建foregroud BroadcastQueue 用于广播        mBgBroadcastQueue = new BroadcastQueue(this, "background", BROADCAST_BG_TIMEOUT); // 创建backgroud BroadcastQueue 用于广播        mBroadcastQueues[0] = mFgBroadcastQueue;        mBroadcastQueues[1] = mBgBroadcastQueue;        mServices = new ActiveServices(this); // 用于Service        mProviderMap = new ProviderMap(this);// 用于记录contentprovider的authority和class        File dataDir = Environment.getDataDirectory(); // init.rc 中是/data        File systemDir = new File(dataDir, "system"); // data/system        systemDir.mkdirs();        mBatteryStatsService = new BatteryStatsService(new File(                systemDir, "batterystats.bin").toString());// data/system/battrtstats.bin 收集影响电池的信息        mBatteryStatsService.getActiveStatistics().readLocked();        mBatteryStatsService.getActiveStatistics().writeAsyncLocked();        mOnBattery = DEBUG_POWER ? true                : mBatteryStatsService.getActiveStatistics().getIsOnBattery();        mBatteryStatsService.getActiveStatistics().setCallback(this);        mUsageStatsService = new UsageStatsService(new File(                systemDir, "usagestats").toString()); // 收集各个组件使用情况 // data/system/usagesstats        mAppOpsService = new AppOpsService(new File(systemDir, "appops.xml"));//权限管理 data/system/ appops.xml        mHeadless = "1".equals(SystemProperties.get("ro.config.headless", "0")); // 对后面开启launcher有作用        // User 0 is the first and only user that runs at boot.        mStartedUsers.put(0, new UserStartedState(new UserHandle(0), true));        mUserLru.add(Integer.valueOf(0));        updateStartedUserArrayLocked();        GL_ES_VERSION = SystemProperties.getInt("ro.opengles.version",            ConfigurationInfo.GL_ES_VERSION_UNDEFINED);        mConfiguration.setToDefaults();        mConfiguration.setLocale(Locale.getDefault());        mConfigurationSeq = mConfiguration.seq = 1;        mProcessStats.init(); // 初始化用于收集进程信息的         // data/system/ packages-compat.xml        mCompatModePackages = new CompatModePackages(this, systemDir);        // Add ourself to the Watchdog monitors.        Watchdog.getInstance().addMonitor(this); // watchdog 监视        mProcessStatsThread = new Thread("ProcessStats") {            public void run() {                while (true) {                    try {                        try {                            synchronized(this) {                                final long now = SystemClock.uptimeMillis();                                long nextCpuDelay = (mLastCpuTime.get()+MONITOR_CPU_MAX_TIME)-now;                                long nextWriteDelay = (mLastWriteTime+BATTERY_STATS_TIME)-now;                                //Slog.i(TAG, "Cpu delay=" + nextCpuDelay                                //        + ", write delay=" + nextWriteDelay);                                if (nextWriteDelay < nextCpuDelay) {                                    nextCpuDelay = nextWriteDelay;                                }                                if (nextCpuDelay > 0) {                                    mProcessStatsMutexFree.set(true);                                    this.wait(nextCpuDelay);                                }                            }                        } catch (InterruptedException e) {                        }                        updateCpuStatsNow();                    } catch (Exception e) {                        Slog.e(TAG, "Unexpected exception collecting process stats", e);                    }                }            }        };        mProcessStatsThread.start(); // 开启线程监视cpu状况    }

而ActivityManager完成如上操作,创建了用于广播的BroadcastQueue,用于Service的ActiveService，

用于记录电池使用的BatteryStatsService

http://blog.csdn.net/z642010820/article/details/7341469，

用于收集各个组件使用情况的UsageStatsService，

用于权限管理的AppOpsService

（http://blog.mssun.me/security/android-4-3-app-ops-analysis/）

用于package 兼容的CompatModePackages

 

还有监视CPU状态的thread

 

做完了初始化工作，Athread notify，执行

ActivityThread at = ActivityThread.systemMain();        mSystemThread = at;

我们看看systemMain做了什么

public static ActivityThread systemMain() {        HardwareRenderer.disable(true); // 把硬件渲染禁掉        ActivityThread thread = new ActivityThread(); // 创建ActivityThread        thread.attach(true);        return thread;    }

 private void attach(boolean system) {        sCurrentActivityThread = this;        mSystemThread = system;        if (!system) { // 如果不是系统            ViewRootImpl.addFirstDrawHandler(new Runnable() {                public void run() {                    ensureJitEnabled();                }            }); // 增加FirstDrawHandler            android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",                                                    UserHandle.myUserId());            RuntimeInit.setApplicationObject(mAppThread.asBinder()); // 设置ApplicationThread，RuntimeInit是runtime初始化主入口            IActivityManager mgr = ActivityManagerNative.getDefault(); // 获取并设置默认的ActivityManager            try {                mgr.attachApplication(mAppThread);// 设置appThread            } catch (RemoteException ex) {                // Ignore            }        } else {// 是系统            // Don't set application object here -- if the system crashes,            // we can't display an alert, we just want to die die die.            android.ddm.DdmHandleAppName.setAppName("system_process",                                                    UserHandle.myUserId());            try {                mInstrumentation = new Instrumentation(); // 创建Instrumentation                ContextImpl context = new ContextImpl(); // 创建系统Context实例                context.init(getSystemContext().mPackageInfo, null, this);// 初始化context                Application app = Instrumentation.newApplication(Application.class, context); //创建APP并CONTEXT设置到APP里面                mAllApplications.add(app); // 把app加入应用程序列表                mInitialApplication = app;                app.onCreate(); // 回调app的onCreate            } catch (Exception e) {                throw new RuntimeException(                        "Unable to instantiate Application():" + e.toString(), e);            }        }        // add dropbox logging to libcore        DropBox.setReporter(new DropBoxReporter());        // 增加config改变的callback，一旦有改变，则发送CONFIGURATION_CHANGED        ViewRootImpl.addConfigCallback(new ComponentCallbacks2() {            public void onConfigurationChanged(Configuration newConfig) {                synchronized (mPackages) {                    // We need to apply this change to the resources                    // immediately, because upon returning the view                    // hierarchy will be informed about it.                    if (applyConfigurationToResourcesLocked(newConfig, null)) {                        // This actually changed the resources!  Tell                        // everyone about it.                        if (mPendingConfiguration == null ||                                mPendingConfiguration.isOtherSeqNewer(newConfig)) {                            mPendingConfiguration = newConfig;                                                        queueOrSendMessage(H.CONFIGURATION_CHANGED, newConfig);                        }                    }                }            }            public void onLowMemory() {            }            public void onTrimMemory(int level) {            }        });    }

在这一步走的system，创建Instrumentation，创建系统Context实例，初始化context，

创建APP并CONTEXT设置到APP里面，把app加入应用程序列表，回调app的onCreate，

增加config改变的callback，一旦有改变，则发送CONFIGURATION_CHANGED

 

在里面有个比较重要

context.init(getSystemContext().mPackageInfo, null, this);

public ContextImpl getSystemContext() {        synchronized (this) {            if (mSystemContext == null) {                ContextImpl context =                    ContextImpl.createSystemContext(this); //创建systemcontext                LoadedApk info = new LoadedApk(this, "android", context, null,                        CompatibilityInfo.DEFAULT_COMPATIBILITY_INFO);                context.init(info, null, this); // context初始化info，res，asset，dm，configuration                context.getResources().updateConfiguration(                        getConfiguration(), getDisplayMetricsLocked(                                Display.DEFAULT_DISPLAY,                                CompatibilityInfo.DEFAULT_COMPATIBILITY_INFO));                mSystemContext = context;                //Slog.i(TAG, "Created system resources " + context.getResources()                //        + ": " + context.getResources().getConfiguration());            }        }        return mSystemContext;    }

可以看到创建了一个systemcontext，而且loadapk与context关系，起关系图如下

接着看看ActivityStack

m.mMainStack = new ActivityStack(m, context, true, thr.mLooper);

ActivityStack(ActivityManagerService service, Context context, boolean mainStack, Looper looper) {        mHandler = new ActivityStackHandler(looper);// 创建ActivityStack消息处理        mService = service;        mContext = context;        mMainStack = mainStack;        PowerManager pm =            (PowerManager)context.getSystemService(Context.POWER_SERVICE);        mGoingToSleep = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "ActivityManager-Sleep"); // 取得 电源控制应用层的锁        mLaunchingActivity = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "ActivityManager-Launch"); // 取得 电源控制应用层的锁        mLaunchingActivity.setReferenceCounted(false);  // 设置为不需要计数    }

 从上面可知，创建了ActivityStack消息处理的handle回调，初始化变量，还有电管管理，而ActivityStackHandler主要处理SLEEP_TIMEOUT_MSG，PAUSE_TIMEOUT_MSG，IDLE_TIMEOUT_MSG，LAUNCH_TICK_MSG，DESTROY_TIMEOUT_MSG，IDLE_NOW_MSG，

LAUNCH_TIMEOUT_MSG，RESUME_TOP_ACTIVITY_MSG，STOP_TIMEOUT_MSG，DESTROY_ACTIVITIES_MSG等

 

继续看main函数

m.mIntentFirewall = new IntentFirewall(m.new IntentFirewallInterface());        m.mBatteryStatsService.publish(context);        m.mUsageStatsService.publish(context);        m.mAppOpsService.publish(context);

主要创建IntentFirewall，而IntentFirewall从/data/system/ifw/ifw.xml or /data/secure/system/ifw/ifw.xml读取出来activity，broadcast，service，并时刻监听着文件是否改变 ，而IntentFirewallInterface则是看是否是ActivityManagerService的进程id

 

而下面BatteryStatsService，UsageStatsService，AppOpsService.则是把服务注册掉binder manager

 

接着继续分析main

 m.startRunning(null, null, null, null);

public final void startRunning(String pkg, String cls, String action,            String data) {        synchronized(this) {            if (mStartRunning) {                return;            }            mStartRunning = true;            mTopComponent = pkg != null && cls != null                    ? new ComponentName(pkg, cls) : null; // 带进来的是null，所以没创建            mTopAction = action != null ? action : Intent.ACTION_MAIN; // 带进来是null，所以是Intent.ACTION_MAIN            mTopData = data; // 为null            if (!mSystemReady) { // 为false ，返回                return;            }        }        systemReady(null);//     }

因为带入的参数都是null，所以只是设置了mTopAction为Intent.ACTION_MAIN，mTopData为null,而mSystemReady为false，

第一步就结束跟踪到这里，ActivityManagerService main函数跑完，回到systemserver

Slog.i(TAG, "Display Manager");            display = new DisplayManagerService(context, wmHandler, uiHandler);            ServiceManager.addService(Context.DISPLAY_SERVICE, display, true);            Slog.i(TAG, "Telephony Registry");            telephonyRegistry = new TelephonyRegistry(context);            ServiceManager.addService("telephony.registry", telephonyRegistry);            Slog.i(TAG, "Scheduling Policy");            ServiceManager.addService(Context.SCHEDULING_POLICY_SERVICE,                    new SchedulingPolicyService());            AttributeCache.init(context);            if (!display.waitForDefaultDisplay()) {                reportWtf("Timeout waiting for default display to be initialized.",                        new Throwable());            }            Slog.i(TAG, "Package Manager");            // Only run "core" apps if we're encrypting the device.            String cryptState = SystemProperties.get("vold.decrypt");            if (ENCRYPTING_STATE.equals(cryptState)) {                Slog.w(TAG, "Detected encryption in progress - only parsing core apps");                onlyCore = true;            } else if (ENCRYPTED_STATE.equals(cryptState)) {                Slog.w(TAG, "Device encrypted - only parsing core apps");                onlyCore = true;            }            pm = PackageManagerService.main(context, installer,                    factoryTest != SystemServer.FACTORY_TEST_OFF,                    onlyCore);            boolean firstBoot = false;            try {                firstBoot = pm.isFirstBoot();            } catch (RemoteException e) {            } ActivityManagerService.setSystemProcess();

增加了DisplayManagerService，TelephonyRegistry，SchedulingPolicyService，PackageManagerService，之后又有跟ActivityManagerService有关的setSystemProcess

public static void setSystemProcess() {        try {            ActivityManagerService m = mSelf;            ServiceManager.addService("activity", m, true); //增加activity的service            ServiceManager.addService("meminfo", new MemBinder(m));// 增加meminfo的service            ServiceManager.addService("gfxinfo", new GraphicsBinder(m)); // 增加gfxinfo的service            ServiceManager.addService("dbinfo", new DbBinder(m));// 增加dbinfo的service            if (MONITOR_CPU_USAGE) {                ServiceManager.addService("cpuinfo", new CpuBinder(m)); // 增加cpuinfo的service            }            ServiceManager.addService("permission", new PermissionController(m)); // 增加检查permission的service            ApplicationInfo info =                mSelf.mContext.getPackageManager().getApplicationInfo(                            "android", STOCK_PM_FLAGS);            mSystemThread.installSystemApplicationInfo(info); // 通过调用mSystemThread.installSystemApplicationInfo函数来把应用程序框架层下面的android包加载进来                   synchronized (mSelf) {                ProcessRecord app = mSelf.newProcessRecordLocked(                        mSystemThread.getApplicationThread(), info,                        info.processName, false);                app.persistent = true;                app.pid = MY_PID;                app.maxAdj = ProcessList.SYSTEM_ADJ;                mSelf.mProcessNames.put(app.processName, app.uid, app);                synchronized (mSelf.mPidsSelfLocked) {                    mSelf.mPidsSelfLocked.put(app.pid, app);                }                mSelf.updateLruProcessLocked(app, true);            }        } catch (PackageManager.NameNotFoundException e) {            throw new RuntimeException(                    "Unable to find android system package", e);        }    }

可以看出android包信息加载了后，刷新了一下进程信息

我们回到systemserver

Slog.i(TAG, "Entropy Mixer");            ServiceManager.addService("entropy", new EntropyMixer(context));            Slog.i(TAG, "User Service");            ServiceManager.addService(Context.USER_SERVICE,                    UserManagerService.getInstance());            mContentResolver = context.getContentResolver();            // The AccountManager must come before the ContentService            try {                Slog.i(TAG, "Account Manager");                accountManager = new AccountManagerService(context);                ServiceManager.addService(Context.ACCOUNT_SERVICE, accountManager);            } catch (Throwable e) {                Slog.e(TAG, "Failure starting Account Manager", e);            }            Slog.i(TAG, "Content Manager");            contentService = ContentService.main(context,                    factoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL);            Slog.i(TAG, "System Content Providers");            ActivityManagerService.installSystemProviders();

加入Entropy Mixer，User Service，Account Manager，Content Manager后调用了installSystemProviders

public static final void installSystemProviders() {        List<ProviderInfo> providers;        synchronized (mSelf) {            ProcessRecord app = mSelf.mProcessNames.get("system", Process.SYSTEM_UID); //  得到名字为system的进程            providers = mSelf.generateApplicationProvidersLocked(app); //  得到所有与此进程相关的Providers            if (providers != null) {                for (int i=providers.size()-1; i>=0; i--) {                    ProviderInfo pi = (ProviderInfo)providers.get(i);                    if ((pi.applicationInfo.flags&ApplicationInfo.FLAG_SYSTEM) == 0) {                        Slog.w(TAG, "Not installing system proc provider " + pi.name                                + ": not system .apk");                        providers.remove(i);                    }                }            }        }        if (providers != null) {            mSystemThread.installSystemProviders(providers); // 通知客户端(ActivityThread)初始化providers        }        mSelf.mCoreSettingsObserver = new CoreSettingsObserver(mSelf);        mSelf.mUsageStatsService.monitorPackages();    }

// 初始化providers private void installContentProviders(            Context context, List<ProviderInfo> providers) {        final ArrayList<IActivityManager.ContentProviderHolder> results =            new ArrayList<IActivityManager.ContentProviderHolder>();        for (ProviderInfo cpi : providers) {            if (DEBUG_PROVIDER) {                StringBuilder buf = new StringBuilder(128);                buf.append("Pub ");                buf.append(cpi.authority);                buf.append(": ");                buf.append(cpi.name);                Log.i(TAG, buf.toString());            }            IActivityManager.ContentProviderHolder cph = installProvider(context, null, cpi,                    false /*noisy*/, true /*noReleaseNeeded*/, true /*stable*/);            if (cph != null) {                cph.noReleaseNeeded = true;                results.add(cph);            }        }        try {            ActivityManagerNative.getDefault().publishContentProviders(                getApplicationThread(), results);        } catch (RemoteException ex) {        }    }

初始化system provider后，

ActivityManagerService.self().setWindowManager(wm);

设置Windowmanager到activityManagerServices里面

最后设置了安全模式，还有开启其他service systemready

还有com.android.systemui.SystemUIService

当然，还有最重要开启launcher的流程

 ActivityManagerService.self().systemReady(new Runnable() {            public void run() {                Slog.i(TAG, "Making services ready");                try {                    ActivityManagerService.self().startObservingNativeCrashes(); // 开始监视native是否crash                } catch (Throwable e) {                    reportWtf("observing native crashes", e);                }.....}}

而真正比较核心的是systemReady函数

 public void systemReady(final Runnable goingCallback) {        synchronized(this) {            if (mSystemReady) { // 为false 不走这条路线                if (goingCallback != null) goingCallback.run();                return;            }                        // Check to see if there are any update receivers to run.            if (!mDidUpdate) { // 之前没初始化过，走这条路线                if (mWaitingUpdate) { // false                    return;                }                Intent intent = new Intent(Intent.ACTION_PRE_BOOT_COMPLETED);                List<ResolveInfo> ris = null;                  try {// 从androidmanifest.xml获取有注册ACTION_PRE_BOOT_COMPLETED的                    ris = AppGlobals.getPackageManager().queryIntentReceivers(                            intent, null, 0, 0);                } catch (RemoteException e) {                }                if (ris != null) { // 如果有则                    for (int i=ris.size()-1; i>=0; i--) {                        if ((ris.get(i).activityInfo.applicationInfo.flags                                &ApplicationInfo.FLAG_SYSTEM) == 0) { // 不是systemimage的则删除掉                            ris.remove(i);                        }                    }                    intent.addFlags(Intent.FLAG_RECEIVER_BOOT_UPGRADE); // 增加FLAG_RECEIVER_BOOT_UPGRADE// data/system/called_pre_boots.dat 读取出之前完成的recevier                    ArrayList<ComponentName> lastDoneReceivers = readLastDonePreBootReceivers();                    final ArrayList<ComponentName> doneReceivers = new ArrayList<ComponentName>();                    for (int i=0; i<ris.size(); i++) {                        ActivityInfo ai = ris.get(i).activityInfo;                        ComponentName comp = new ComponentName(ai.packageName, ai.name);                        if (lastDoneReceivers.contains(comp)) { // 如果有包含之前完成的就删除掉                            ris.remove(i);                            i--;                        }                    }                   final int[] users = getUsersLocked();                    for (int i=0; i<ris.size(); i++) {                        ActivityInfo ai = ris.get(i).activityInfo;                        ComponentName comp = new ComponentName(ai.packageName, ai.name);                        doneReceivers.add(comp);                        intent.setComponent(comp);                        for (int j=0; j<users.length; j++) {                            IIntentReceiver finisher = null;                            if (i == ris.size()-1 && j == users.length-1) {                                finisher = new IIntentReceiver.Stub() {                                    public void performReceive(Intent intent, int resultCode,                                            String data, Bundle extras, boolean ordered,                                            boolean sticky, int sendingUser) {                                        // The raw IIntentReceiver interface is called                                        // with the AM lock held, so redispatch to                                        // execute our code without the lock.                                        mHandler.post(new Runnable() {                                            public void run() {                                                synchronized (ActivityManagerService.this) {                                                    mDidUpdate = true;                                                }                                                writeLastDonePreBootReceivers(doneReceivers);                                                showBootMessage(mContext.getText(                                                        R.string.android_upgrading_complete),                                                        false);                                                systemReady(goingCallback);                                            }                                        });                                    }                                };                            }                            Slog.i(TAG, "Sending system update to " + intent.getComponent()                                    + " for user " + users[j]);// 发送广播                            broadcastIntentLocked(null, null, intent, null, finisher,                                    0, null, null, null, AppOpsManager.OP_NONE,                                    true, false, MY_PID, Process.SYSTEM_UID,                                    users[j]);                            if (finisher != null) {                                mWaitingUpdate = true;                            }                        }                    }                }                if (mWaitingUpdate) { // false                    return;                }                mDidUpdate = true; // 被设置为true            }            mAppOpsService.systemReady(); // appOps 准备            mSystemReady = true; // 再次设置为true            if (!mStartRunning) { // 为true                return;            }        }       ArrayList<ProcessRecord> procsToKill = null;        synchronized(mPidsSelfLocked) {// mPidsSelfLocked 为 0            for (int i=mPidsSelfLocked.size()-1; i>=0; i--) {                ProcessRecord proc = mPidsSelfLocked.valueAt(i);                if (!isAllowedWhileBooting(proc.info)){                    if (procsToKill == null) {                        procsToKill = new ArrayList<ProcessRecord>();                    }                    procsToKill.add(proc);                }            }        }                synchronized(this) {//  procsToKill 为null            if (procsToKill != null) {                for (int i=procsToKill.size()-1; i>=0; i--) {                    ProcessRecord proc = procsToKill.get(i);                    Slog.i(TAG, "Removing system update proc: " + proc);                    removeProcessLocked(proc, true, false, "system update done");                }            }                        // Now that we have cleaned up any update processes, we            // are ready to start launching real processes and know that            // we won't trample on them any more.            mProcessesReady = true; // 把mProcessesReady 设置为true        }                Slog.i(TAG, "System now ready");        EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_AMS_READY,            SystemClock.uptimeMillis());        synchronized(this) {            // Make sure we have no pre-ready processes sitting around.            // 不是测试模式，不走这步            if (mFactoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL) {                ResolveInfo ri = mContext.getPackageManager()                        .resolveActivity(new Intent(Intent.ACTION_FACTORY_TEST),                                STOCK_PM_FLAGS);                CharSequence errorMsg = null;                if (ri != null) {                    ActivityInfo ai = ri.activityInfo;                    ApplicationInfo app = ai.applicationInfo;                    if ((app.flags&ApplicationInfo.FLAG_SYSTEM) != 0) {                        mTopAction = Intent.ACTION_FACTORY_TEST;                        mTopData = null;                        mTopComponent = new ComponentName(app.packageName,                                ai.name);                    } else {                        errorMsg = mContext.getResources().getText(                                com.android.internal.R.string.factorytest_not_system);                    }                } else {                    errorMsg = mContext.getResources().getText(                            com.android.internal.R.string.factorytest_no_action);                }                if (errorMsg != null) {                    mTopAction = null;                    mTopData = null;                    mTopComponent = null;                    Message msg = Message.obtain();                    msg.what = SHOW_FACTORY_ERROR_MSG;                    msg.getData().putCharSequence("msg", errorMsg);                    mHandler.sendMessage(msg);                }            }        }// 获取setting的配置 读取content://settings/global 里面debug，finishactivity等值        retrieveSettings();       // 其他service systemready        if (goingCallback != null) goingCallback.run();                synchronized (this) {// 不是测试模式，但是packagemanagerservice还没有            if (mFactoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {                try {     // 读取固化的app                    List apps = AppGlobals.getPackageManager().                        getPersistentApplications(STOCK_PM_FLAGS);                    if (apps != null) {                        int N = apps.size();                        int i;                        for (i=0; i<N; i++) {                            ApplicationInfo info                                = (ApplicationInfo)apps.get(i);                            if (info != null &&                                    !info.packageName.equals("android")) {                                addAppLocked(info, false);                            }                        }                    }                } catch (RemoteException ex) {                    // pm is in same process, this will never happen.                }           }            // Start up initial activity.            mBooting = true;  // 设置booting完成     //             try {                if (AppGlobals.getPackageManager().hasSystemUidErrors()) { // 是否有system uid error                    Message msg = Message.obtain();                    msg.what = SHOW_UID_ERROR_MSG;                    mHandler.sendMessage(msg);                }            } catch (RemoteException e) {            }            long ident = Binder.clearCallingIdentity();            try {                Intent intent = new Intent(Intent.ACTION_USER_STARTED);                intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY                        | Intent.FLAG_RECEIVER_FOREGROUND);                intent.putExtra(Intent.EXTRA_USER_HANDLE, mCurrentUserId);// 发送广播                broadcastIntentLocked(null, null, intent,                        null, null, 0, null, null, null, AppOpsManager.OP_NONE,                        false, false, MY_PID, Process.SYSTEM_UID, mCurrentUserId);                intent = new Intent(Intent.ACTION_USER_STARTING);                intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);                intent.putExtra(Intent.EXTRA_USER_HANDLE, mCurrentUserId);// 发送广播                broadcastIntentLocked(null, null, intent,                        null, new IIntentReceiver.Stub() {                            @Override                            public void performReceive(Intent intent, int resultCode, String data,                                    Bundle extras, boolean ordered, boolean sticky, int sendingUser)                                    throws RemoteException {                            }                        }, 0, null, null,                        android.Manifest.permission.INTERACT_ACROSS_USERS, AppOpsManager.OP_NONE,                        true, false, MY_PID, Process.SYSTEM_UID, UserHandle.USER_ALL);            } finally {                Binder.restoreCallingIdentity(ident);            }    // 开启top activity            mMainStack.resumeTopActivityLocked(null);           sendUserSwitchBroadcastsLocked(-1, mCurrentUserId);        }    }

里面最主要的是resumeTopActivityLocked函数

final boolean resumeTopActivityLocked(ActivityRecord prev, Bundle options) {        // Find the first activity that is not finishing.        ActivityRecord next = topRunningActivityLocked(null); // 在history activityrecord里面查找未结束的activity        // Remember how we'll process this pause/resume situation, and ensure        // that the state is reset however we wind up proceeding.        final boolean userLeaving = mUserLeaving;        mUserLeaving = false;        if (next == null) { // 因为第一次，所有为null，所以跑这一步            // There are no more activities!  Let's just start up the            // Launcher...            if (mMainStack) {                ActivityOptions.abort(options);                return mService.startHomeActivityLocked(mCurrentUser); // 在这一步开启了Launcher            }        }       。。。。。。        return true;    }

我们可以看到此时这个函数主要是开启launcher

我们看怎么开启launcher的

boolean startHomeActivityLocked(int userId) {        if (mHeadless) {  // 是否没有head，不走            // Added because none of the other calls to ensureBootCompleted seem to fire            // when running headless.            ensureBootCompleted();            return false;        }// 不是测试模式，不走        if (mFactoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL                && mTopAction == null) {            // We are running in factory test mode, but unable to find            // the factory test app, so just sit around displaying the            // error message and don't try to start anything.            return false;        }// 此时mTopAction为main，mTopComponent为null mTopData 为null        Intent intent = new Intent(            mTopAction,            mTopData != null ? Uri.parse(mTopData) : null);        intent.setComponent(mTopComponent);        if (mFactoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {// 再增加CATEGORY_HOME            intent.addCategory(Intent.CATEGORY_HOME);        }        ActivityInfo aInfo =            resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);//         if (aInfo != null) { // 得到launcher            intent.setComponent(new ComponentName(                    aInfo.applicationInfo.packageName, aInfo.name));            // Don't do this if the home app is currently being            // instrumented.            aInfo = new ActivityInfo(aInfo);            aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId);            ProcessRecord app = getProcessRecordLocked(aInfo.processName,                    aInfo.applicationInfo.uid);            if (app == null || app.instrumentationClass == null) {                intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);                mMainStack.startActivityLocked(null, intent, null, aInfo,                        null, null, 0, 0, 0, null, 0, null, false, null); // 开启launcher            }        }        return true;        }

private ActivityInfo resolveActivityInfo(Intent intent, int flags, int userId) {        ActivityInfo ai = null;        ComponentName comp = intent.getComponent();        try {            if (comp != null) {                ai = AppGlobals.getPackageManager().getActivityInfo(comp, flags, userId);            } else {                 ResolveInfo info = AppGlobals.getPackageManager().resolveIntent(                        intent,                        intent.resolveTypeIfNeeded(mContext.getContentResolver()),                            flags, userId); // 获取出之前intent带的 resolveInfo ，在里面选择了最合适的resolveInfo回来                    if (info != null) {                    ai = info.activityInfo;                }            }        } catch (RemoteException e) {            // ignore        }        return ai;    }

最后用

mMainStack.startActivityLocked(null, intent, null, aInfo,                        null, null, 0, 0, 0, null, 0, null, false, null);

开启了launcher

一个activity启动过程