概述
ActivityManager主要功能有：
①启动或杀死应用程序进程。
②启动调度Activyty生命周期。
③注册Broadcast Receiver，接收分发Broadcast。
④启动发布Content Provocer。
⑤task相关。
⑥OOM。
ActivityManagerService是在SystemServer启动过程中启动的，代码如下。
private void startBootstrapServices() {
// Wait for installd to finish starting up so that it has a chance to
// create critical directories such as /data/user with the appropriate
// permissions. We need this to complete before we initialize other services.
Installer installer = mSystemServiceManager.startService(Installer.class);
// Activity manager runs the show.
//①启动Liifcycle，进而启动ActivityManagerService
mActivityManagerService = mSystemServiceManager.startService(
ActivityManagerService.Lifecycle.class).getService();
mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
mActivityManagerService.setInstaller(installer);
……
// Set up the Application instance for the system process and get started.
//②调用setSystemProcess()方法。
mActivityManagerService.setSystemProcess();
……
private void startOtherServices() {
final Context context = mSystemContext;
AccountManagerService accountManager = null;
ContentService contentService = null;
VibratorService vibrator = null;
……
Slog.i(TAG, "System Content Providers");
//③调用installSystemProviders方法。
mActivityManagerService.installSystemProviders();
……
//④调用systemReday方法
mActivityManagerService.systemReady(new Runnable() {
@Override
public void run() {
Slog.i(TAG, "Making services ready");
mSystemServiceManager.startBootPhase(
SystemService.PHASE_ACTIVITY_MANAGER_READY);
try {
mActivityManagerService.startObservingNativeCrashes();
} catch (Throwable e) {
reportWtf("observing native crashes", e);
}
Slog.i(TAG, "WebViewFactory preparation");
WebViewFactory.prepareWebViewInSystemServer();
try {
startSystemUi(context);
} catch (Throwable e) {
reportWtf("starting System UI", e);
}
try {
if (networkScoreF != null) networkScoreF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Score Service ready", e);
}下面详细分析每个步骤。
1.第一阶段，启动ActivityManagerService。
mActivityManagerService = mSystemServiceManager.startService(
ActivityManagerService.Lifecycle.class).getService();
//通过反射获取到会启动ActivityManagerService构造方法。
} public ActivityManagerService(Context systemContext) {
mContext = systemContext;
mFactoryTest = FactoryTest.getMode();
mSystemThread = ActivityThread.currentActivityThread();
mHandlerThread = new ServiceThread(TAG,
android.os.Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
mHandlerThread.start();
mHandler = new MainHandler(mHandlerThread.getLooper());//启动Handler相关
mUiHandler = new UiHandler();
mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
"foreground", BROADCAST_FG_TIMEOUT, false);
mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
"background", BROADCAST_BG_TIMEOUT, true);
mBroadcastQueues[0] = mFgBroadcastQueue;
mBroadcastQueues[1] = mBgBroadcastQueue;
mServices = new ActiveServices(this);
mProviderMap = new ProviderMap(this);
// TODO: Move creation of battery stats service outside of activity manager service.
File dataDir = Environment.getDataDirectory();// /data
File systemDir = new File(dataDir, "system");// /data/system
systemDir.mkdirs();
mBatteryStatsService = new BatteryStatsService(systemDir, mHandler);
……
mCompatModePackages = new CompatModePackages(this, systemDir, mHandler);
mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);
mRecentTasks = new RecentTasks(this);
mStackSupervisor = new ActivityStackSupervisor(this, mRecentTasks);
mTaskPersister = new TaskPersister(systemDir, mStackSupervisor, mRecentTasks);//task相关
mProcessCpuThread = new Thread("CpuTracker") {
@Override
public void run() {
……
}
};
Watchdog.getInstance().addMonitor(this);
Watchdog.getInstance().addThread(mHandler);
}2.第二阶段，调用setSystemProcess()方法。
public void setSystemProcess() {
try {
//加入各种服务
ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);
ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
ServiceManager.addService("meminfo", new MemBinder(this));
ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
ServiceManager.addService("dbinfo", new DbBinder(this));
if (MONITOR_CPU_USAGE) {
ServiceManager.addService("cpuinfo", new CpuBinder(this));
}
ServiceManager.addService("permission", new PermissionController(this));
ServiceManager.addService("processinfo", new ProcessInfoService(this));
ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
"android", STOCK_PM_FLAGS);//framework-res
mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
synchronized (this) {
//生成ProcessRecord类型的app
ProcessRecord app = newProcessRecordLocked(info, info.processName, false, 0);
app.persistent = true;//常驻内存
app.pid = MY_PID;
app.maxAdj = ProcessList.SYSTEM_ADJ;
app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
synchronized (mPidsSelfLocked) {
mPidsSelfLocked.put(app.pid, app);
}
//更新lru与adj
updateLruProcessLocked(app, false, null);
updateOomAdjLocked();
}
} catch (PackageManager.NameNotFoundException e) {
throw new RuntimeException(
"Unable to find android system package", e);
}
第二阶段主要是，首先注册各种服务，查询并处理ApplicationInfo,首先调用PackageManagerService接口，查询报名为"android"的应用程序的ApplicationInfo信息，该信息来自Android启动时的APK的安装扫描过程，对应于framework-res.apk，然后电泳installSystemmApplicationIfo方法。然后创建并处理ProcessRecord。</pre><p>3.第三阶段，调用installSystemProviders方法。</p><p></p><pre name="code" class="java">public final void installSystemProviders() {
List<ProviderInfo> providers;
synchronized (this) {
//取出进程名为"system"，user_id为SYSTEM_UID的进程信息
ProcessRecord app = mProcessNames.get("system", Process.SYSTEM_UID);
//生成运行在system进程中的providerInfo，表示一个Content Provider。
providers = generateApplicationProvidersLocked(app);
if (providers != null) {
for (int i=providers.size()-1; i>=0; i--) {
ProviderInfo pi = (ProviderInfo)providers.get(i);
//过滤掉非系统apk
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) {
//安装provider
mSystemThread.installSystemProviders(providers);
}
//监听Settings数据库变化。
mCoreSettingsObserver = new CoreSettingsObserver(this);
//mUsageStatsService.monitorPackages();
4.第四阶段，调用systemReday方法。
public void systemReady(final Runnable goingCallback) {
synchronized(this) {
//默认为false，执行完systemReday方法后赋值为true
if (mSystemReady) {
// If we're done calling all the receivers, run the next "boot phase" passed in
// by the SystemServer
if (goingCallback != null) {
goingCallback.run();
}
return;
}
mLocalDeviceIdleController
= LocalServices.getService(DeviceIdleController.LocalService.class);
// Make sure we have the current profile info, since it is needed for
// security checks.
updateCurrentProfileIdsLocked();
mRecentTasks.clear();
mRecentTasks.addAll(mTaskPersister.restoreTasksLocked());
mRecentTasks.cleanupLocked(UserHandle.USER_ALL);
mTaskPersister.startPersisting();//RecentTask相关。
// Check to see if there are any update receivers to run.
if (!mDidUpdate) {
if (mWaitingUpdate) {
return;
}
final ArrayList<ComponentName> doneReceivers = new ArrayList<ComponentName>();
//发送ACTION_PRE_BOOT_COMPLETED广播，只启动一次。
mWaitingUpdate = deliverPreBootCompleted(new Runnable() {
public void run() {
synchronized (ActivityManagerService.this) {
mDidUpdate = true;
}
showBootMessage(mContext.getText(
R.string.android_upgrading_complete),
false);
writeLastDonePreBootReceivers(doneReceivers);
systemReady(goingCallback);
}
}, doneReceivers, UserHandle.USER_OWNER);
if (mWaitingUpdate) {
return;
}
mDidUpdate = true;
}
mAppOpsService.systemReady();
mSystemReady = true;
}
ArrayList<ProcessRecord> procsToKill = null;
synchronized(mPidsSelfLocked) {
for (int i=mPidsSelfLocked.size()-1; i>=0; i--) {
ProcessRecord proc = mPidsSelfLocked.valueAt(i);
//找到不允许预先启动的进程，非persistent进程不允许预先启动
if (!isAllowedWhileBooting(proc.info)){
if (procsToKill == null) {
procsToKill = new ArrayList<ProcessRecord>();
}
procsToKill.add(proc);
}
}
}
synchronized(this) {
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;
}
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.
if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL) {
//test相关
……
}
//读取Settings配置
retrieveSettings();
loadResourcesOnSystemReady();
synchronized (this) {
readGrantedUriPermissionsLocked();
}
//回调 Runnable接口
if (goingCallback != null) goingCallback.run();
mBatteryStatsService.noteEvent(BatteryStats.HistoryItem.EVENT_USER_RUNNING_START,
Integer.toString(mCurrentUserId), mCurrentUserId);
mBatteryStatsService.noteEvent(BatteryStats.HistoryItem.EVENT_USER_FOREGROUND_START,
Integer.toString(mCurrentUserId), mCurrentUserId);
mSystemServiceManager.startUser(mCurrentUserId);
synchronized (this) {
if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
try {
//获取persistent应用程序的ApplicationInfo
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);
//过滤掉framework-res.apk，因为已经启动
if (info != null &&
!info.packageName.equals("android")) {
addAppLocked(info, false, null /* ABI override */);
}
}
}
} catch (RemoteException ex) {
// pm is in same process, this will never happen.
}
}
// Start up initial activity.
mBooting = true;//mBooting赋值为true，即可发送ACTION_BOOT_COMPLETE广播
//start Home
startHomeActivityLocked(mCurrentUserId, "systemReady");
try {
if (AppGlobals.getPackageManager().hasSystemUidErrors()) {
Slog.e(TAG, "UIDs on the system are inconsistent, you need to wipe your"
+ " data partition or your device will be unstable.");
mUiHandler.obtainMessage(SHOW_UID_ERROR_MSG).sendToTarget();
}
} catch (RemoteException e) {
}
……
//启动栈顶第一个Activity,默认为home
mStackSupervisor.resumeTopActivitiesLocked();
sendUserSwitchBroadcastsLocked(-1, mCurrentUserId);
}
}
mActivityManagerService.systemReady(new Runnable() {
@Override
public void run() {
Slog.i(TAG, "Making services ready");
mSystemServiceManager.startBootPhase(
SystemService.PHASE_ACTIVITY_MANAGER_READY);
……
try {
//启动SystemUI
startSystemUi(context);
} catch (Throwable e) {
reportWtf("starting System UI", e);
}
try {
if (networkScoreF != null) networkScoreF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Score Service ready", e);
}
……
try {
if (mmsServiceF != null) mmsServiceF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying MmsService running", e);
}
}
});
}第四阶段大致功能概况为：发送ACTION_PRE_BOOT_COMPLETE方法，清理启动的persistent进程，读取Settings配置，运行runnable接口，启动SystemUI，启动persistent应用程序，启动home，发送ACTION_BOOT_COMPLETE广播
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