和你一起终身学习，这里是程序员 Android
本篇文章主要介绍 Android 开发中的部分知识点，通过阅读本篇文章，您将收获以下内容:
一、AMS 是如何启动的？
二、通过 Lifecycle 启动初始化 AMS 系统服务
三、AMS 构造函数实例实现
四、启动AMS.Start()方法实现
五、AMS设置系统进程实现
六、AMS 安装系统 Provider实现
七、AMS.systemReady准备完成
八、AMS 启动 Launcher实现
一、AMS 是如何启动的？
AMS（ActivityManagerService 简称）是通过SystemServer.java (frameworks\base\services\java\com\android\server\SystemServer.java)类中的 startBootstrapServices() 方法启动的。
1. startBootstrapServices主要作用
startBootstrapServices 主要是启动以下引导服务，引导系统Service 起来。
部分通过系统服务如下：
- Installer安装服务、
- Activity管理服务AMS、
- 电源管理服务PowerManagerService、
- Recovery管理服务RecoverySystemService、
- LED 背光显示服务LightsService、
- 显示管理服务DisplayManagerService、
- app 包管理服务PackageManagerService等。
2.AMS启动流程
AMS启动大致流程如下：
- SystemServer.main
- SystemServer.SystemServer()
- SystemServer.run()
- SystemServer.startBootstrapServices()
AMS启动详细流程如下：
public final class SystemServer {
... ...
/**
* The main entry point from zygote.
*/
public static void main(String[] args) {
new SystemServer().run();
}
public SystemServer() {
... ...
mRuntimeRestart = "1".equals(SystemProperties.get("sys.boot_completed"));
... ...
}
private void run() {
... ...
//启动系统服务
try {
traceBeginAndSlog("StartServices");
// 系统引导服务启动，比如：AMS 启动
startBootstrapServices();
startCoreServices();
startOtherServices();
resetSerial();
SystemServerInitThreadPool.shutdown();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
} finally {
traceEnd();
}
... ...
// Set up the Application instance for the system process and get started.
traceBeginAndSlog("SetSystemProcess");
//设置系统进程 详见 五
mActivityManagerService.setSystemProcess();
traceEnd();
... ...
}
//系统引导服务启动的方法
private void startBootstrapServices() {
... ...
// Activity manager runs the show.
traceBeginAndSlog("StartActivityManager");
// 通过 Lifecycle 启动 AMS 系统服务流程，详见 二
mActivityManagerService = mSystemServiceManager.startService(
ActivityManagerService.Lifecycle.class).getService();
mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
mActivityManagerService.setInstaller(installer);
traceEnd();
... ...
}
private void startOtherServices() {
... ...
// 调用AMS 的 安装系统Provider installSystemProviders 方法，详见步骤 六
traceBeginAndSlog("InstallSystemProviders");
mActivityManagerService.installSystemProviders();
// Now that SettingsProvider is ready, reactivate SQLiteCompatibilityWalFlags
SQLiteCompatibilityWalFlags.reset();
traceEnd();
... ...
// 系统准备完毕，可以让第三代码调用 详见 步骤七
mActivityManagerService.systemReady(() -> {
Slog.i(TAG, "Making services ready");
traceBeginAndSlog("StartActivityManagerReadyPhase");
// ActivityManager 准备完毕
mSystemServiceManager.startBootPhase(
SystemService.PHASE_ACTIVITY_MANAGER_READY);
traceEnd();
... ...
}, BOOT_TIMINGS_TRACE_LOG);
}
... ...
}
二、 通过 Lifecycle 启动初始化 AMS 系统服务
1. 静态全局 Lifecycle 类
在 AMS 中，我们看到静态全局的 final Lifecycle 类对外提供 getService()方法，方便供 SystemServer类调用。
调用方法如下：
// 通过 Lifecycle 启动 AMS 系统服务流程，详见 二
mActivityManagerService = mSystemServiceManager.startService(
ActivityManagerService.Lifecycle.class).getService();
2. AMS 继承实现关系
AMS 的继承关系如下：
public class ActivityManagerService extends IActivityManager.Stub
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
... ...
}
AMS 继承实现关系图如下：
AMS 继承实现关系图
从上图我们可以看出
1.AMS 继承IActivityManager.Stub类
2.AMS 实现Watchdog.Monitor和BatteryStatsImpl.BatteryCallback接口。
3.通过 Lifecycle 启动初始化 AMS 系统服务实现
AMS 是通过Lifecycle启动 AMS 并实现初始化。
具体实现代码如下：
public class ActivityManagerService extends IActivityManager.Stub
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
... ...
public static final class Lifecycle extends SystemService {
private final ActivityManagerService mService;
public Lifecycle(Context context) {
super(context);
// new ActivityManagerService 实例 见分析三
mService = new ActivityManagerService(context);
}
@Override
public void onStart() {
// 启动AMS ，见分析四
mService.start();
}
... ...
public ActivityManagerService getService() {
return mService;
}
}
... ...
}
三、AMS 构造函数实例实现
通过 mService = new ActivityManagerService(context);，调用 AMS 构造函数，并运行在主线程中（main Thread），需要注意的是，AMS 中有多个Handler，请在loop 的时候注意，不要使用错了。
1. AMS 构造函数主要实现的功能
- 创建
ActivityManager、android.ui、ActivityManager:procStart、ActivityManager:kill服务线程。 - 设置前台广播、后台广播的超时时间。
- 设置后台Service 最大个数(8个，低 RAM 1个)
- 初始化 系统 Provider，以及AppErrors、AppWarnings。
- 创建
/data/system目录，并保存procstats、appops.xml等文件。 - 创建 Intent 防火墙
IntentFirewall，以及Activity 带来对象ActivityStartController。 - 创建
CpuTracker线程 ，收集ANRS，电池电量信息，更新CPU 状态等。 - 获取 Watchdog 实例，并将AMS 添加到看门狗Monitor中，以及将mHandler 添加到看门狗 线程中。
- 更新 oom_adj 状态。
2. AMS 构造函数实现方法
AMS 构造函数实现如下：
public ActivityManagerService(Context systemContext) {
... ...
//创建名为"ActivityManager"的前台线程，并获取mHandler
// TAG 线程名，请看ActivityManagerDebugConfig，
//默认 TAG_AM 即为 ActivityManager
mHandlerThread = new ServiceThread(TAG,
THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
mHandlerThread.start();
mHandler = new MainHandler(mHandlerThread.getLooper());
//通过UiThread类，创建名为"android.ui"的线程
mUiHandler = mInjector.getUiHandler(this);
//创建名为"ActivityManager:procStart"的前台线程，并获取mProcStartHandler
mProcStartHandlerThread = new ServiceThread(TAG + ":procStart",
THREAD_PRIORITY_FOREGROUND, false /* allowIo */);
mProcStartHandlerThread.start();
mProcStartHandler = new Handler(mProcStartHandlerThread.getLooper());
//创建可以修改ActivityManager实例的对象
mConstants = new ActivityManagerConstants(this, mHandler);
//不重复创建 “ActivityManager:kill”后台线程，并获取sKillHandler
if (sKillHandler == null) {
sKillThread = new ServiceThread(TAG + ":kill",
THREAD_PRIORITY_BACKGROUND, true /* allowIo */);
sKillThread.start();
sKillHandler = new KillHandler(sKillThread.getLooper());
}
//前台广播接收器，在运行超过10s将放弃执行
mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
"foreground", BROADCAST_FG_TIMEOUT, false);
//后台广播接收器，在运行超过60s将放弃执行
mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
"background", BROADCAST_BG_TIMEOUT, true);
mBroadcastQueues[0] = mFgBroadcastQueue;
mBroadcastQueues[1] = mBgBroadcastQueue;
//创建ActiveServices，其中非低内存手机后台服务最大为8个
// mMaxStartingBackground = maxBg > 0
// ? maxBg : ActivityManager.isLowRamDeviceStatic() ? 1 : 8;
mServices = new ActiveServices(this);
//创建 系统 Provider
mProviderMap = new ProviderMap(this);
// 创建 Apperror 对象
mAppErrors = new AppErrors(mUiContext, this);
//创建目录/data/system
File dataDir = Environment.getDataDirectory();
File systemDir = new File(dataDir, "system");
systemDir.mkdirs();
// 创建 管理 app Warning 的Dialog
mAppWarnings = new AppWarnings(this, mUiContext, mHandler, mUiHandler, systemDir);
//创建服务BatteryStatsService
mBatteryStatsService = new BatteryStatsService(systemContext, systemDir, mHandler);
mBatteryStatsService.getActiveStatistics().readLocked();
mBatteryStatsService.scheduleWriteToDisk();
mOnBattery = DEBUG_POWER ? true
: mBatteryStatsService.getActiveStatistics().getIsOnBattery();
mBatteryStatsService.getActiveStatistics().setCallback(this);
//创建进程统计服务，信息保存在目录/data/system/procstats
mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));
mAppOpsService = mInjector.getAppOpsService(new File(systemDir, "appops.xml"), mHandler);
mGrantFile = new AtomicFile(new File(systemDir, "urigrants.xml"), "uri-grants");
//创建多用户、VR controller
mUserController = new UserController(this);
mVrController = new VrController(this);
... ...
// 创建 Intent 防火墙
mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);
mTaskChangeNotificationController =
new TaskChangeNotificationController(this, mStackSupervisor, mHandler);
// 创建控制 Activity 启动代理对象
mActivityStartController = new ActivityStartController(this);
// 创建最近任务列表，并保存在最近任务列表栈中
mRecentTasks = createRecentTasks();
mStackSupervisor.setRecentTasks(mRecentTasks);
// 创建 任务栈锁，比如在Screen pinning Mode 下
mLockTaskController = new LockTaskController(mContext, mStackSupervisor, mHandler);
mLifecycleManager = new ClientLifecycleManager();
//创建名为"CpuTracker"的线程， 主要用于 收集 ANRS、电池状态信息等
mProcessCpuThread = new Thread("CpuTracker") {
@Override
public void run() {
synchronized (mProcessCpuTracker) {
mProcessCpuInitLatch.countDown();
mProcessCpuTracker.init();
}
... ...
// 更新CPU 状态
updateCpuStatsNow();
... ...
}
};
mHiddenApiBlacklist = new HiddenApiSettings(mHandler, mContext);
// 获取 Watchdog看门狗实例 ，并添加到Monitor监控 以及mHandler 添加到Thread中
Watchdog.getInstance().addMonitor(this);
Watchdog.getInstance().addThread(mHandler);
// 更新 oom_adj
updateOomAdjLocked();
... ...
}
3.后台Service 最大限制数设置
class ActivityManagerDebugConfig {
... ...
static final boolean TAG_WITH_CLASS_NAME = false;
// Default log tag for the activity manager package.
static final String TAG_AM = "ActivityManager";
... ...
}
四、启动AMS.Start() 实现
1.AMS.Start() 主要功能
- 移除所有的进程组
- 启动CpuTracker线程
- 启动 app 操作服务AppOpsService
- 将ActivityManagerInternal 添加到本地Service中
2.AMS.Start() 功能 实现
AMS.Start() 功能实现如下：
private void start() {
//移除所有的进程组
removeAllProcessGroups();
//启动CpuTracker线程
mProcessCpuThread.start();
//启动电池统计服务
mBatteryStatsService.publish();
// 启动 app 操作Service
mAppOpsService.publish(mContext);
Slog.d("AppOps", "AppOpsService published");
// 将ActivityManagerInternal 添加到本地Service中
LocalServices.addService(ActivityManagerInternal.class, new LocalService());
}
五、AMS设置系统进程实现
setSystemProcess 主要作用是
添加 各种服务 包括meminfo、gfxinfo、dbinfo、cpuinfo以及permission和processinfo系统Service。同时， 更新进程相关的 Lru 算法 ，以及oom_adj 值。
实现代码如下：
public void setSystemProcess() {
try {
//注册添加各种Service，可以使用adb shell dumpsys
ServiceManager.addService(Context.ACTIVITY_SERVICE, this, /* allowIsolated= */ true,
DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PRIORITY_NORMAL | DUMP_FLAG_PROTO);
ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
//adb shell dumpsys meminfo 注册内存信息Service
ServiceManager.addService("meminfo", new MemBinder(this), /* allowIsolated= */ false,
DUMP_FLAG_PRIORITY_HIGH);
//adb shell dumpsys gfxinfo 注册GraphicsBinder
ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
//adb shell dumpsys dbinfo 注册 DbBinder
ServiceManager.addService("dbinfo", new DbBinder(this));
if (MONITOR_CPU_USAGE) {
//adb shell dumpsys cpuinfo 注册CPU 信息Service
ServiceManager.addService("cpuinfo", new CpuBinder(this),
/* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
}
//adb shell dumpsys packages permissions 注册 系统权限 信息Service
ServiceManager.addService("permission", new PermissionController(this));
ServiceManager.addService("processinfo", new ProcessInfoService(this));
// 获取包名为 android 的应用信息，framework-res.apk
ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
"android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);
mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
synchronized (this) {
ProcessRecord app = newProcessRecordLocked(info, info.processName, false, 0);
app.persistent = true;
app.pid = MY_PID;
app.maxAdj = ProcessList.SYSTEM_ADJ;
app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
synchronized (mPidsSelfLocked) {
mPidsSelfLocked.put(app.pid, app);
}
//更新 进程 Lru 算法 ，以及oom_adj 值
updateLruProcessLocked(app, false, null);
updateOomAdjLocked();
}
}
// 当 packager manager 启动并运行时开始监听 app 操作
mAppOpsService.startWatchingMode(AppOpsManager.OP_RUN_IN_BACKGROUND, null,
new IAppOpsCallback.Stub() {
@Override public void opChanged(int op, int uid, String packageName) {
if (op == AppOpsManager.OP_RUN_IN_BACKGROUND && packageName != null) {
if (mAppOpsService.checkOperation(op, uid, packageName)
!= AppOpsManager.MODE_ALLOWED) {
runInBackgroundDisabled(uid);
}
}
}
});
}
六、安装系统 Provider
通过 SystemServer.java 类中的startOtherServices()方法mActivityManagerService.installSystemProviders();调用 AMS中的installSystemProviders方法。
下面我们看看installSystemProviders 方法的主要功能
public final void installSystemProviders() {
List providers;
synchronized (this) {
ProcessRecord app = mProcessNames.get("system", SYSTEM_UID);
providers = generateApplicationProvidersLocked(app);
if (providers != null) {
for (int i=providers.size()-1; i>=0; i--) {
ProviderInfo pi = (ProviderInfo)providers.get(i);
// 1&1=1 1&0=0 0&0=0
if ((pi.applicationInfo.flags&ApplicationInfo.FLAG_SYSTEM) == 0) {
Slog.w(TAG, "Not installing system proc provider " + pi.name
+ ": not system .apk");
//移除非系统 app
providers.remove(i);
}
}
}
}
... ...
mConstants.start(mContext.getContentResolver());
// 创建 CoreSettingsObserver ，监控核心设置的变化
mCoreSettingsObserver = new CoreSettingsObserver(this);
// 创建 FontScaleSettingObserver，监控字体的变化
mFontScaleSettingObserver = new FontScaleSettingObserver();
// 创建 DevelopmentSettingsObserver 监控开发者选项
mDevelopmentSettingsObserver = new DevelopmentSettingsObserver();
GlobalSettingsToPropertiesMapper.start(mContext.getContentResolver());
//对外公布 settings provider
RescueParty.onSettingsProviderPublished(mContext);
//mUsageStatsService.monitorPackages();
}
七、AMS.systemReady准备完成
SystemServer 中的 AMS.systemReady 主要完成以下功能
- 确保系统Service已经准备完成。
- ActivityManager 引导启动完成。
- 开始监听NativeCrash。
- WebView 准备完毕，方便三方apk 调用。
- 启动车载相关的服务。
- 启动SystemUI。
- 确保 MakeNetworkManagementService 准备完成。
- 启动 Watchdog 看门狗程序。
- 等待所有的app数据预加载，然后，可以启动三方app。
- Location、telephony、输入法、Media、MMS、Daemon等相关的Service已经运行并准备好
SystemServer中具体实现代码情况下文：
public final class SystemServer {
... ...
/**
* The main entry point from zygote.
*/
public static void main(String[] args) {
new SystemServer().run();
}
public SystemServer() {
... ...
}
private void run() {
... ...
//启动系统服务
startOtherServices();
... ...
}
private void startOtherServices() {
... ...
// 系统准备完毕，可以让第三代码调用
mActivityManagerService.systemReady(() -> {
Slog.i(TAG, "Making services ready");
traceBeginAndSlog("StartActivityManagerReadyPhase");
// ActivityManager 准备完毕
mSystemServiceManager.startBootPhase(
SystemService.PHASE_ACTIVITY_MANAGER_READY);
traceEnd();
traceBeginAndSlog("StartObservingNativeCrashes");
try {
// 开始监听 Native Crash
mActivityManagerService.startObservingNativeCrashes();
} catch (Throwable e) {
reportWtf("observing native crashes", e);
}
traceEnd();
//WebView 准备好，方便三方apk 调用
final String WEBVIEW_PREPARATION = "WebViewFactoryPreparation";
Future webviewPrep = null;
if (!mOnlyCore && mWebViewUpdateService != null) {
webviewPrep = SystemServerInitThreadPool.get().submit(() -> {
Slog.i(TAG, WEBVIEW_PREPARATION);
TimingsTraceLog traceLog = new TimingsTraceLog(
SYSTEM_SERVER_TIMING_ASYNC_TAG, Trace.TRACE_TAG_SYSTEM_SERVER);
traceLog.traceBegin(WEBVIEW_PREPARATION);
ConcurrentUtils.waitForFutureNoInterrupt(mZygotePreload, "Zygote preload");
mZygotePreload = null;
mWebViewUpdateService.prepareWebViewInSystemServer();
traceLog.traceEnd();
}, WEBVIEW_PREPARATION);
}
// 启动车载相关的服务
if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_AUTOMOTIVE)) {
traceBeginAndSlog("StartCarServiceHelperService");
mSystemServiceManager.startService(CAR_SERVICE_HELPER_SERVICE_CLASS);
traceEnd();
}
// 启动SystemUI
traceBeginAndSlog("StartSystemUI");
try {
startSystemUi(context, windowManagerF);
} catch (Throwable e) {
reportWtf("starting System UI", e);
}
traceEnd();
// MakeNetworkManagementService 准备完成
traceBeginAndSlog("MakeNetworkManagementServiceReady");
try {
if (networkManagementF != null) networkManagementF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Managment Service ready", e);
}
CountDownLatch networkPolicyInitReadySignal = null;
if (networkPolicyF != null) {
networkPolicyInitReadySignal = networkPolicyF
.networkScoreAndNetworkManagementServiceReady();
}
traceEnd();
traceBeginAndSlog("MakeIpSecServiceReady");
try {
if (ipSecServiceF != null) ipSecServiceF.systemReady();
} catch (Throwable e) {
reportWtf("making IpSec Service ready", e);
}
traceEnd();
traceBeginAndSlog("MakeNetworkStatsServiceReady");
try {
if (networkStatsF != null) networkStatsF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Stats Service ready", e);
}
traceEnd();
traceBeginAndSlog("MakeConnectivityServiceReady");
try {
if (connectivityF != null) connectivityF.systemReady();
} catch (Throwable e) {
reportWtf("making Connectivity Service ready", e);
}
traceEnd();
traceBeginAndSlog("MakeNetworkPolicyServiceReady");
try {
if (networkPolicyF != null) {
networkPolicyF.systemReady(networkPolicyInitReadySignal);
}
} catch (Throwable e) {
reportWtf("making Network Policy Service ready", e);
}
traceEnd();
// 启动 Watchdog 看门狗程序
traceBeginAndSlog("StartWatchdog");
Watchdog.getInstance().start();
traceEnd();
//等待所有的app数据预加载
mPackageManagerService.waitForAppDataPrepared();
// It is now okay to let the various system services start their
// third party code...
traceBeginAndSlog("PhaseThirdPartyAppsCanStart");
// confirm webview completion before starting 3rd party
if (webviewPrep != null) {
ConcurrentUtils.waitForFutureNoInterrupt(webviewPrep, WEBVIEW_PREPARATION);
}
// 三方 app 已准备好，可以启动
mSystemServiceManager.startBootPhase(
SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);
traceEnd();
traceBeginAndSlog("MakeLocationServiceReady");
try {
// 定位服务已经运行，并准备好
if (locationF != null) locationF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying Location Service running", e);
}
traceEnd();
traceBeginAndSlog("MakeCountryDetectionServiceReady");
try {
if (countryDetectorF != null) countryDetectorF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying CountryDetectorService running", e);
}
traceEnd();
traceBeginAndSlog("MakeNetworkTimeUpdateReady");
try {
if (networkTimeUpdaterF != null) networkTimeUpdaterF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying NetworkTimeService running", e);
}
traceEnd();
traceBeginAndSlog("MakeCommonTimeManagementServiceReady");
try {
if (commonTimeMgmtServiceF != null) {
commonTimeMgmtServiceF.systemRunning();
}
} catch (Throwable e) {
reportWtf("Notifying CommonTimeManagementService running", e);
}
traceEnd();
traceBeginAndSlog("MakeInputManagerServiceReady");
try {
// 输入法相关的Service已经运行并准备好
// TODO(BT) Pass parameter to input manager
if (inputManagerF != null) inputManagerF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying InputManagerService running", e);
}
traceEnd();
traceBeginAndSlog("MakeTelephonyRegistryReady");
try {
// telephony相关的Service已经运行并准备好
if (telephonyRegistryF != null) telephonyRegistryF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying TelephonyRegistry running", e);
}
traceEnd();
traceBeginAndSlog("MakeMediaRouterServiceReady");
try {
// media 相关的Service已经运行并准备好
if (mediaRouterF != null) mediaRouterF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying MediaRouterService running", e);
}
traceEnd();
traceBeginAndSlog("MakeMmsServiceReady");
try {
// 短信 相关的Service已经运行并准备好
if (mmsServiceF != null) mmsServiceF.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying MmsService running", e);
}
traceEnd();
traceBeginAndSlog("IncidentDaemonReady");
try {
// TODO: Switch from checkService to getService once it's always
// in the build and should reliably be there.
final IIncidentManager incident = IIncidentManager.Stub.asInterface(
ServiceManager.getService(Context.INCIDENT_SERVICE));
if (incident != null) incident.systemRunning();
} catch (Throwable e) {
reportWtf("Notifying incident daemon running", e);
}
traceEnd();
}, BOOT_TIMINGS_TRACE_LOG);
}
... ...
}
AMS 中 SystemReady 主要作用有以下功能
- kill 掉非persistent app进程。
- 检测 Setting中的一些配置索引。
- 注册低电量模式的关闭。
- 启动 persistent app。
- 启动Home Activity 比如Launcher
- 恢复显示TopActivity
具体实现代码如下：
public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) {
traceLog.traceBegin("PhaseActivityManagerReady");
synchronized(this) {
if (mSystemReady) {
// 如果我们完成所有的receiver 调用，然后需要调用 SystemServer 的boot phase 方法
if (goingCallback != null) {
goingCallback.run();
}
return;
}
... ...
// 确保 VR 、多用户控制、最近任务列表、最近app操作已完成
mVrController.onSystemReady();
mUserController.onSystemReady();
mRecentTasks.onSystemReadyLocked();
mAppOpsService.systemReady();
mSystemReady = true;
}
... ...
// 非 persistent 应用都会添加到kill list中
ArrayList procsToKill = null;
synchronized(mPidsSelfLocked) {
for (int i=mPidsSelfLocked.size()-1; i>=0; i--) {
ProcessRecord proc = mPidsSelfLocked.valueAt(i);
// 判断是否是persistent 应用
if (!isAllowedWhileBooting(proc.info)){
if (procsToKill == null) {
procsToKill = new ArrayList();
}
procsToKill.add(proc);
}
}
}
synchronized(this) {
if (procsToKill != null) {
for (int i=procsToKill.size()-1; i>=0; i--) {
ProcessRecord proc = procsToKill.get(i);
//杀掉非persistent 应用
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) {
... ...
// 检索Settings的一些信息
// 比如多用户、画中画、分屏、fullScreen等
retrieveSettings();
final int currentUserId = mUserController.getCurrentUserId();
synchronized (this) {
// 读取授权的URI 权限文件
readGrantedUriPermissionsLocked();
}
final PowerManagerInternal pmi = LocalServices.getService(PowerManagerInternal.class);
if (pmi != null) {
// 注册并更新低电量模式广播
pmi.registerLowPowerModeObserver(ServiceType.FORCE_BACKGROUND_CHECK,
state -> updateForceBackgroundCheck(state.batterySaverEnabled));
updateForceBackgroundCheck(
pmi.getLowPowerState(ServiceType.FORCE_BACKGROUND_CHECK).batterySaverEnabled);
} else {
Slog.wtf(TAG, "PowerManagerInternal not found.");
}
... ...
synchronized (this) {
// 启动 persistent app
startPersistentApps(PackageManager.MATCH_DIRECT_BOOT_AWARE);
// Start up initial activity.
mBooting = true;
// Enable home activity for system user, so that the system can always boot. We don't
// do this when the system user is not setup since the setup wizard should be the one
// to handle home activity in this case.
if (UserManager.isSplitSystemUser() &&
Settings.Secure.getInt(mContext.getContentResolver(),
Settings.Secure.USER_SETUP_COMPLETE, 0) != 0) {
ComponentName cName = new ComponentName(mContext, SystemUserHomeActivity.class);
try {
AppGlobals.getPackageManager().setComponentEnabledSetting(cName,
PackageManager.COMPONENT_ENABLED_STATE_ENABLED, 0,
UserHandle.USER_SYSTEM);
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
}
// 启动 Home Activity ，比如 通过 StartHomeActivity(inten,ainfo,myReason) 启动Launcher
// 启动 Launcher方法请见 步骤八
startHomeActivityLocked(currentUserId, "systemReady");
long ident = Binder.clearCallingIdentity();
try {
// 发送 ACTION_USER_STARTED 的广播
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, currentUserId);
broadcastIntentLocked(null, null, intent,
null, null, 0, null, null, null, OP_NONE,
null, false, false, MY_PID, SYSTEM_UID,
currentUserId);
// 发送 ACTION_USER_STARTING 的广播
intent = new Intent(Intent.ACTION_USER_STARTING);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
intent.putExtra(Intent.EXTRA_USER_HANDLE, currentUserId);
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,
new String[] {INTERACT_ACROSS_USERS}, OP_NONE,
null, true, false, MY_PID, SYSTEM_UID, UserHandle.USER_ALL);
} catch (Throwable t) {
Slog.wtf(TAG, "Failed sending first user broadcasts", t);
} finally {
Binder.restoreCallingIdentity(ident);
}
// 恢复显示Top Activity
mStackSupervisor.resumeFocusedStackTopActivityLocked();
mUserController.sendUserSwitchBroadcasts(-1, currentUserId);
... ...
traceLog.traceEnd(); // ActivityManagerStartApps
traceLog.traceEnd(); // PhaseActivityManagerReady
}
}
八、 AMS 启动 Launcher实现
startHomeActivityLocked 主要用来启动Home Launcher，具体实现代码如下:
boolean startHomeActivityLocked(int userId, String reason) {
if (mFactoryTest == FactoryTest.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;
}
// 获取 Intent.CATEGORY_HOME intent
Intent intent = getHomeIntent();
ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
if (aInfo != null) {
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, true);
if (app == null || app.instr == null) {
intent.setFlags(intent.getFlags() | FLAG_ACTIVITY_NEW_TASK);
final int resolvedUserId = UserHandle.getUserId(aInfo.applicationInfo.uid);
// For ANR debugging to verify if the user activity is the one that actually
// launched.
final String myReason = reason + ":" + userId + ":" + resolvedUserId;
// 启动Home Activity
mActivityStartController.startHomeActivity(intent, aInfo, myReason);
}
} else {
Slog.wtf(TAG, "No home screen found for " + intent, new Throwable());
}
return true;
}
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