《深入理解Android2》读书笔记（四）
2024-10-21 05:10:20
接上篇《深入理解Android2》读书笔记（三）
ActivityManagerService（AMS）
1.AMS由ActivityManagerNative（AMN）类派生，并实现Watchdog.Monitor和BatteryStatsImpl.BatteryCallback接口。而AMN由Binder派生，实现了IActivityManager接口。
2.客户端使用ActivityManager类。由于AMS是系统核心服务，很多API不能开放供客户端使用，因此设计者没有让ActivityManager直接加入AMS家庭。ActivityManager类内部通过调用AMN的getDefault函数得到一个ActivityManagerProxy对象，通过它可与AMS通信。
public static final Context main(int factoryTest){
AThread thr = new AThread();//创建一个AThread线程对象
thr.start();
ActivityManagerService m = thr.mService;
mSelf = m;
//调用ActivityThread的systemMain函数
ActivityThread at = ActivityThread.systemMain();
mSystemThread = at;
//得到一个Context对象，注意调用的函数名为getSystemContext,何为System Context
Context context = at.getSystemContext();
context.setTheme(android.R.style.Theme_Holo);
m.mContext = context;
m.mFactoryTest = factoryTest;
//ActivityStack是AMS中用来管理Activity的启动和调度的核心类，以后再分析它
m.mMainStack = new ActivityStack(m,context,true);
//调用BSS的public函数，这个知识点我们在第5章介绍过了
m.mBatteryStatsService.publish(context);
//另外一个service：UsageStatsService.读者阅读完本章后自行分析它
m.mUsageStatsService.publish(context);
synchronized(thr){
thr.mReady = true;
thr.notifyAll();//通知thr线程，本线程工作完成
}
//调用AMS的startRunning函数
m.startRunning(null,null,null,null);
return context;
}
其中四个函数分别是
1.创建AThread线程。虽然AMS的main函数由ServerThread线程调用，但是AMS自己的工作并没有放在ServerThread中去做，而是新创建了一个线程，即AThread线程
2.ActivityThread.systemMain函数。初始化ActivityThread对象
3.ActivityThread.getSystemContext函数。用于获取一个Context对象，从函数名上看，该Context代表了System的上下文环境。
4.AMS的startRunning函数。
main函数中有一处等待（wait）、一处通知（notifyAll），因为
1.main函数首先需要等到AThread所在线程启动并完成一部分工作
2.AThread完成那一部分工作后，将等待main函数完成后续的工作
以上函数我在SDK23的版本并没有找到，权当记录了，下面来分析构造函数
public ActivityManagerService(Context systemContext) {
mContext = systemContext;
mFactoryTest = FactoryTest.getMode();
mSystemThread = ActivityThread.currentActivityThread();
Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass());
mHandlerThread = new ServiceThread(TAG,
android.os.Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
mHandlerThread.start();
mHandler = new MainHandler(mHandlerThread.getLooper());
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();
File systemDir = new File(dataDir, "system");
systemDir.mkdirs();
mBatteryStatsService = new BatteryStatsService(systemDir, mHandler);
mBatteryStatsService.getActiveStatistics().readLocked();
mBatteryStatsService.scheduleWriteToDisk();
mOnBattery = DEBUG_POWER ? true
: mBatteryStatsService.getActiveStatistics().getIsOnBattery();
mBatteryStatsService.getActiveStatistics().setCallback(this);
mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));
mAppOpsService = new AppOpsService(new File(systemDir, "appops.xml"), mHandler);
mGrantFile = new AtomicFile(new File(systemDir, "urigrants.xml"));
// User 0 is the first and only user that runs at boot.
mStartedUsers.put(UserHandle.USER_OWNER, new UserState(UserHandle.OWNER, true));
mUserLru.add(UserHandle.USER_OWNER);
updateStartedUserArrayLocked();
GL_ES_VERSION = SystemProperties.getInt("ro.opengles.version",
ConfigurationInfo.GL_ES_VERSION_UNDEFINED);
mTrackingAssociations = "1".equals(SystemProperties.get("debug.track-associations"));
mConfiguration.setToDefaults();
mConfiguration.setLocale(Locale.getDefault());
mConfigurationSeq = mConfiguration.seq = 1;
mProcessCpuTracker.init();
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);
mProcessCpuThread = new Thread("CpuTracker") {
@Override
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) {
mProcessCpuMutexFree.set(true);
this.wait(nextCpuDelay);
}
}
} catch (InterruptedException e) {
}
updateCpuStatsNow();
} catch (Exception e) {
Slog.e(TAG, "Unexpected exception collecting process stats", e);
}
}
}
};
Watchdog.getInstance().addMonitor(this);
Watchdog.getInstance().addThread(mHandler);
}
1.创建BSS、USS、mProcessStats（ProcessStats类型）、mProcessStatsThread线程，这些都与系统运行状况统计相关
2.创建/data/system目录，为mCompatModePackages（CompatModePackages类型）和mConfiguration（Configuration类型）等成员变量赋值
ActivityThread
ActivityThread是Android Framework中一个非常重要的类，它代表一个应用进程的主线程（对于应用进程来说，ActivityThread的main函数确实是由该进程的主线程执行），其职责就是调度及执行在该线程中的四大组件。
应用进程指那些运行APK的进程，它们由Zyote派生（fork）而来，上面运行了dalvik虚拟机。与应用进程相对的就是系统进程（包括Zygote和system_server）。如果apk文件在/data/app目录下，则为应用apk
public static ActivityThread systemMain() {
// The system process on low-memory devices do not get to use hardware
// accelerated drawing, since this can add too much overhead to the
// process.
if (!ActivityManager.isHighEndGfx()) {
HardwareRenderer.disable(true);
} else {
HardwareRenderer.enableForegroundTrimming();
}
ActivityThread thread = new ActivityThread();
thread.attach(true);
return thread;
}
通过ActivityThread可以把Android系统提供的组件之间的交互机制和交互接口（如利用Context提供的API）也拓展到system_server中使用。
private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {
ViewRootImpl.addFirstDrawHandler(new Runnable() {
@Override
public void run() {
ensureJitEnabled();
}
});
android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",
UserHandle.myUserId());
RuntimeInit.setApplicationObject(mAppThread.asBinder());
final IActivityManager mgr = ActivityManagerNative.getDefault();
try {
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
// Ignore
}
// Watch for getting close to heap limit.
BinderInternal.addGcWatcher(new Runnable() {
@Override public void run() {
if (!mSomeActivitiesChanged) {
return;
}
Runtime runtime = Runtime.getRuntime();
long dalvikMax = runtime.maxMemory();
long dalvikUsed = runtime.totalMemory() - runtime.freeMemory();
if (dalvikUsed > ((3*dalvikMax)/4)) {
if (DEBUG_MEMORY_TRIM) Slog.d(TAG, "Dalvik max=" + (dalvikMax/1024)
+ " total=" + (runtime.totalMemory()/1024)
+ " used=" + (dalvikUsed/1024));
mSomeActivitiesChanged = false;
try {
mgr.releaseSomeActivities(mAppThread);
} catch (RemoteException e) {
}
}
}
});
} else {
// 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();
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
// add dropbox logging to libcore
DropBox.setReporter(new DropBoxReporter());
ViewRootImpl.addConfigCallback(new ComponentCallbacks2() {
@Override
public void onConfigurationChanged(Configuration newConfig) {
synchronized (mResourcesManager) {
// We need to apply this change to the resources
// immediately, because upon returning the view
// hierarchy will be informed about it.
if (mResourcesManager.applyConfigurationToResourcesLocked(newConfig, null)) {
// This actually changed the resources! Tell
// everyone about it.
if (mPendingConfiguration == null ||
mPendingConfiguration.isOtherSeqNewer(newConfig)) {
mPendingConfiguration = newConfig;
sendMessage(H.CONFIGURATION_CHANGED, newConfig);
}
}
}
}
@Override
public void onLowMemory() {
}
@Override
public void onTrimMemory(int level) {
}
});
}
attach函数中出现几个重要类型Instrumentation类、Application类及Context类，作用如下
1.Instrumentation是一个工具类，当它被启用时，系统先创建它，再通过它来创建其他组件，另外，系统和组件之间的交互也将通过Instrumentation来传递，这样，Instrumentation就能监测系统和这些组件的交互情况了。在实际使用中，我们可以创建Instrumentation的派生类来进行相应的处理。
2.Application类保存了一个全局的application状态。Application由AndroidManifest.xml中的<applicaion>标签声明。在实际使用时需定义Applicaion的派生类（可以理解为一种容器，其内部包含四大组件。一个进程可以运行多个Application）
3.Context是一个接口，通过它可以获取并操作Application对应的资源、类，甚至包含于Application中的四大组件。
public ContextImpl getSystemContext() {
synchronized (this) {
if (mSystemContext == null) {
mSystemContext = ContextImpl.createSystemContext(this);
}
return mSystemContext;
}
}
1.ApplicationContentResolver从ContentResolver派生，它主要用于和ContentProvider打交道。ContextImpl和ContextWrapper均从Context继承，而Application则从ContextWrapper派生
2.ContextImpl涉及的面最广，它通过mResources指向Resources，通过mPackageInfo指向LoadedApk，通过mMainThread指向ActivityThread，通过mContentResolver指向ApplicationContentResolver。
3.ActivityThread代表主线程，它通过mInstrumentation指向Instrumentation。另外，它还保存多个Application对象。
systemMain函数调用结束后，得到了：
1.得到了一个ActivityThread对象，它代表应用进程的主线程
2.得到了一个Context对象，它背后所指向的Application环境与framework-res.apk有关
systemMain函数的目的是为system_server进程搭建一个和应用进程一样的Android运行环境。
1.ContextWrapper是一个代理类，被代理的对象是另外一个Context，其实是ContextImpl，由ContextWrapper通过mBase成员变量指定。ContextWrapper其内部函数功能的实现最终都由mBase完成，这样设计的目的是想把ContextImpl隐藏起来。
2.Application从ContextWrapper派生，并实现了ComponentCallbacks2接口。Application中有一个LoadedApk类型的成员变量mLoadedApk。LoadedApk代表一个APK文件。由于一个AndroidManifest.xml文件只能声明一个Application标签，所以一个Application必然会和一个LoadedApk绑定。
3.Service从ContextWrapper派生，其中Service内部成员变量mApplication指向Application（在AndroidManifest.xml中，Service只能作为Application的子标签，所以在代码中Service必然会和一个Application绑定）。
4.ContextThemeWrapper重载了和Theme（主题）相关的两个函数。这些和界面有关，所以Activity作为Android系统中的UI容器，必然也会从ContextThemeWrapper派生。与Servcie一样，Activity内部也通过mApplication成员变量指向Application。
public void setSystemProcess() {
try {
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);
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);
}
updateLruProcessLocked(app, false, null);
updateOomAdjLocked();
}
} catch (PackageManager.NameNotFoundException e) {
throw new RuntimeException(
"Unable to find android system package", e);
}
}
Context第一次执行init的目的仅仅是创建一个Android运行环境，而该Context并没有和实际的ApplicationInfo绑定。而第二次执行init前，先利用Context和PKMS交互得到一个实际ApplicationInfo，然后再通过init将此Context和ApplicationInfo绑定。
1.ApplicationThreadNative实现了IApplicationThread接口。从该接口定义的函数可知，AMS通过它可以和应用进程进行交互，例如，AMS启动一个Activity的时候会调用该接口的scheduleLaunchActivity函数
2.ActivityThread通过成员变量mAppThread指向它的内部类ApplicationThread，而ApplicationThread从ApplicationThreadNative派生
3.IApplicationThread的Binder服务端在应用进程中，因为AMS需要监听应用进程的死亡通知。
4.有了IApplicationThread接口，AMS就可以和应用进程交互了。
public final void scheduleStopActivity(IBinder token, boolean showWindow,
int configChanges) {
sendMessage(
showWindow ? H.STOP_ACTIVITY_SHOW : H.STOP_ACTIVITY_HIDE,
token, 0, configChanges);
}
当AMS想要停止（stop）一个Activity时，会调用对应进程IApplicationThread Binder客户端的scheduleStopActivity函数。该函数服务端实现的就是向ActivityThread所在线程发送一个消息。在应用进程中，ActivityThread运行在主线程中，所以这个消息最终在主线程被处理。Activity的onStop函数页将在主线程中被处理。
IApplication Thread仅仅是AMS和另外一个进程交互的接口，除此之外，AMS还需要更多的有关该进程的信息。在AMS中，进程的信息都保存在ProcessRecord数据结构中。
final ProcessRecord newProcessRecordLocked(ApplicationInfo info, String customProcess,
boolean isolated, int isolatedUid) {
String proc = customProcess != null ? customProcess : info.processName;
BatteryStatsImpl stats = mBatteryStatsService.getActiveStatistics();
final int userId = UserHandle.getUserId(info.uid);
int uid = info.uid;
if (isolated) {
if (isolatedUid == 0) {
int stepsLeft = Process.LAST_ISOLATED_UID - Process.FIRST_ISOLATED_UID + 1;
while (true) {
if (mNextIsolatedProcessUid < Process.FIRST_ISOLATED_UID
|| mNextIsolatedProcessUid > Process.LAST_ISOLATED_UID) {
mNextIsolatedProcessUid = Process.FIRST_ISOLATED_UID;
}
uid = UserHandle.getUid(userId, mNextIsolatedProcessUid);
mNextIsolatedProcessUid++;
if (mIsolatedProcesses.indexOfKey(uid) < 0) {
// No process for this uid, use it.
break;
}
stepsLeft--;
if (stepsLeft <= 0) {
return null;
}
}
} else {
// Special case for startIsolatedProcess (internal only), where
// the uid of the isolated process is specified by the caller.
uid = isolatedUid;
}
}
final ProcessRecord r = new ProcessRecord(stats, info, proc, uid);
if (!mBooted && !mBooting
&& userId == UserHandle.USER_OWNER
&& (info.flags & PERSISTENT_MASK) == PERSISTENT_MASK) {
r.persistent = true;
}
addProcessNameLocked(r);
return r;
}
ProcessRecord(BatteryStatsImpl _batteryStats, ApplicationInfo _info,
String _processName, int _uid) {
mBatteryStats = _batteryStats;
info = _info;
isolated = _info.uid != _uid;
uid = _uid;
userId = UserHandle.getUserId(_uid);
processName = _processName;
pkgList.put(_info.packageName, new ProcessStats.ProcessStateHolder(_info.versionCode));
maxAdj = ProcessList.UNKNOWN_ADJ;
curRawAdj = setRawAdj = -100;
curAdj = setAdj = -100;
persistent = false;
removed = false;
lastStateTime = lastPssTime = nextPssTime = SystemClock.uptimeMillis();
}
ProcessRecord除保存和应用进程通信的IApplicationThread对象外，还保存了进程名、不同状态对应的Oom_adj值及一个ApplicationInfo。一个进程虽然可运行多个Application，但是ProcessRecord一般保存该进程中先运行的那个Application的ApplicationInfo。现在，创建了一个ProcessRecord对象，该对象对应的进程为system_server。
AMS的setSystemProcess的工作
1.注册AMS、meminfo、gfxinfo等服务到ServiceManager中
2.根据PKMS返回的ApplicationInfo初始化Android运行环境，并创建一个代表system_server进程的ProcessRecord，从此，system_server进程也并入AMS的管理范围内。
public final void installSystemProviders() {
List<ProviderInfo> providers;
synchronized (this) {
ProcessRecord app = mProcessNames.get("system", Process.SYSTEM_UID);
providers = generateApplicationProvidersLocked(app);
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);
}
mCoreSettingsObserver = new CoreSettingsObserver(this);
//mUsageStatsService.monitorPackages();
}
private final List<ProviderInfo> generateApplicationProvidersLocked(ProcessRecord app) {
List<ProviderInfo> providers = null;
try {
ParceledListSlice<ProviderInfo> slice = AppGlobals.getPackageManager().
queryContentProviders(app.processName, app.uid,
STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS);
providers = slice != null ? slice.getList() : null;
} catch (RemoteException ex) {
}
if (DEBUG_MU) Slog.v(TAG_MU,
"generateApplicationProvidersLocked, app.info.uid = " + app.uid);
int userId = app.userId;
if (providers != null) {
int N = providers.size();
app.pubProviders.ensureCapacity(N + app.pubProviders.size());
for (int i=0; i<N; i++) {
ProviderInfo cpi =
(ProviderInfo)providers.get(i);
boolean singleton = isSingleton(cpi.processName, cpi.applicationInfo,
cpi.name, cpi.flags);
if (singleton && UserHandle.getUserId(app.uid) != UserHandle.USER_OWNER) {
// This is a singleton provider, but a user besides the
// default user is asking to initialize a process it runs
// in... well, no, it doesn't actually run in this process,
// it runs in the process of the default user. Get rid of it.
providers.remove(i);
N--;
i--;
continue;
}
ComponentName comp = new ComponentName(cpi.packageName, cpi.name);
ContentProviderRecord cpr = mProviderMap.getProviderByClass(comp, userId);
if (cpr == null) {
cpr = new ContentProviderRecord(this, cpi, app.info, comp, singleton);
mProviderMap.putProviderByClass(comp, cpr);
}
if (DEBUG_MU) Slog.v(TAG_MU,
"generateApplicationProvidersLocked, cpi.uid = " + cpr.uid);
app.pubProviders.put(cpi.name, cpr);
if (!cpi.multiprocess || !"android".equals(cpi.packageName)) {
// Don't add this if it is a platform component that is marked
// to run in multiple processes, because this is actually
// part of the framework so doesn't make sense to track as a
// separate apk in the process.
app.addPackage(cpi.applicationInfo.packageName, cpi.applicationInfo.versionCode,
mProcessStats);
}
ensurePackageDexOpt(cpi.applicationInfo.packageName);
}
}
return providers;
}
public final void installSystemProviders() {
List<ProviderInfo> providers;
synchronized (this) {
ProcessRecord app = mProcessNames.get("system", Process.SYSTEM_UID);
providers = generateApplicationProvidersLocked(app);
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);
}
mCoreSettingsObserver = new CoreSettingsObserver(this);
//mUsageStatsService.monitorPackages();
}
@Override
public ParceledListSlice<ProviderInfo> queryContentProviders(String processName,
int uid, int flags) {
ArrayList<ProviderInfo> finalList = null;
// reader
synchronized (mPackages) {
final Iterator<PackageParser.Provider> i = mProviders.mProviders.values().iterator();
final int userId = processName != null ?
UserHandle.getUserId(uid) : UserHandle.getCallingUserId();
while (i.hasNext()) {
final PackageParser.Provider p = i.next();
PackageSetting ps = mSettings.mPackages.get(p.owner.packageName);
if (ps != null && p.info.authority != null
&& (processName == null
|| (p.info.processName.equals(processName)
&& UserHandle.isSameApp(p.info.applicationInfo.uid, uid)))
&& mSettings.isEnabledLPr(p.info, flags, userId)
&& (!mSafeMode
|| (p.info.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0)) {
if (finalList == null) {
finalList = new ArrayList<ProviderInfo>(3);
}
ProviderInfo info = PackageParser.generateProviderInfo(p, flags,
ps.readUserState(userId), userId);
if (info != null) {
finalList.add(info);
}
}
}
} if (finalList != null) {
Collections.sort(finalList, mProviderInitOrderSorter);
return new ParceledListSlice<ProviderInfo>(finalList);
} return null;
}
AMS保存ProviderInfo的原因是它要管理ContentProvider。ProcessRecord保存ProviderInfo的原因是ContentProvider最终要落实到一个进程中，其实也是为了方便AMS管理，例如该进程一旦退出，AMS需要把其中的ContentProvider信息从系统中去除。
AMS及ProcessRecord均使用了一个新的数据结构ContentProviderRecord来管理ContentProvider。
1.ContentProviderRecord从ContentProviderHolder派生，内部保存了ProviderInfo、该Provider所驻留的进程ProcessRecord，以及使用该ContentProvider的客户端进程ProcessRecord（即clients成员变量）
2.AMS的mProviderByClass成员变量及ProcessRecord的pubProviders成员变量均以ComponentName为key来保存对应的ContentProviderRecrod对象。
public final void installSystemProviders(List<ProviderInfo> providers) {
if (providers != null) {
installContentProviders(mInitialApplication, 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) {
}
}
installContentProviders实际上是标准的ContentProvider安装时调用的程序。安装ContentProvider包括两方面的工作
1.先在ActivityThread中通过installProvider得到一个ContentProvider实例
2.向AMS发布这个ContentProvider实例。如此这般，一个APK中声明的ContentProvider才能发挥其该有的作用。
private IActivityManager.ContentProviderHolder installProvider(Context context,
IActivityManager.ContentProviderHolder holder, ProviderInfo info,
boolean noisy, boolean noReleaseNeeded, boolean stable) {
ContentProvider localProvider = null;
IContentProvider provider;
if (holder == null || holder.provider == null) {
if (DEBUG_PROVIDER || noisy) {
Slog.d(TAG, "Loading provider " + info.authority + ": "
+ info.name);
}
Context c = null;
ApplicationInfo ai = info.applicationInfo;
if (context.getPackageName().equals(ai.packageName)) {
c = context;
} else if (mInitialApplication != null &&
mInitialApplication.getPackageName().equals(ai.packageName)) {
c = mInitialApplication;
} else {
try {
c = context.createPackageContext(ai.packageName,
Context.CONTEXT_INCLUDE_CODE);
} catch (PackageManager.NameNotFoundException e) {
// Ignore
}
}
if (c == null) {
Slog.w(TAG, "Unable to get context for package " +
ai.packageName +
" while loading content provider " +
info.name);
return null;
}
try {
final java.lang.ClassLoader cl = c.getClassLoader();
localProvider = (ContentProvider)cl.
loadClass(info.name).newInstance();
provider = localProvider.getIContentProvider();
if (provider == null) {
Slog.e(TAG, "Failed to instantiate class " +
info.name + " from sourceDir " +
info.applicationInfo.sourceDir);
return null;
}
if (DEBUG_PROVIDER) Slog.v(
TAG, "Instantiating local provider " + info.name);
// XXX Need to create the correct context for this provider.
localProvider.attachInfo(c, info);
} catch (java.lang.Exception e) {
if (!mInstrumentation.onException(null, e)) {
throw new RuntimeException(
"Unable to get provider " + info.name
+ ": " + e.toString(), e);
}
return null;
}
} else {
provider = holder.provider;
if (DEBUG_PROVIDER) Slog.v(TAG, "Installing external provider " + info.authority + ": "
+ info.name);
} IActivityManager.ContentProviderHolder retHolder; synchronized (mProviderMap) {
if (DEBUG_PROVIDER) Slog.v(TAG, "Checking to add " + provider
+ " / " + info.name);
IBinder jBinder = provider.asBinder();
if (localProvider != null) {
ComponentName cname = new ComponentName(info.packageName, info.name);
ProviderClientRecord pr = mLocalProvidersByName.get(cname);
if (pr != null) {
if (DEBUG_PROVIDER) {
Slog.v(TAG, "installProvider: lost the race, "
+ "using existing local provider");
}
provider = pr.mProvider;
} else {
holder = new IActivityManager.ContentProviderHolder(info);
holder.provider = provider;
holder.noReleaseNeeded = true;
pr = installProviderAuthoritiesLocked(provider, localProvider, holder);
mLocalProviders.put(jBinder, pr);
mLocalProvidersByName.put(cname, pr);
}
retHolder = pr.mHolder;
} else {
ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
if (prc != null) {
if (DEBUG_PROVIDER) {
Slog.v(TAG, "installProvider: lost the race, updating ref count");
}
// We need to transfer our new reference to the existing
// ref count, releasing the old one... but only if
// release is needed (that is, it is not running in the
// system process).
if (!noReleaseNeeded) {
incProviderRefLocked(prc, stable);
try {
ActivityManagerNative.getDefault().removeContentProvider(
holder.connection, stable);
} catch (RemoteException e) {
//do nothing content provider object is dead any way
}
}
} else {
ProviderClientRecord client = installProviderAuthoritiesLocked(
provider, localProvider, holder);
if (noReleaseNeeded) {
prc = new ProviderRefCount(holder, client, 1000, 1000);
} else {
prc = stable
? new ProviderRefCount(holder, client, 1, 0)
: new ProviderRefCount(holder, client, 0, 1);
}
mProviderRefCountMap.put(jBinder, prc);
}
retHolder = prc.holder;
}
} return retHolder;
}
1.ContentProvider类本身只是一个容器，而跨进程调用的支持是通过内部类Transport实现。Transport从ContentProviderNative派生，而ContentProvider的成员变量mTransport指向Transport对象。ContentProvider的getIContentProvider函数即返回mTransport成员变量
2.ContentProviderNative从Binder派生，并实现了IContentProvider接口。其内部类ContentProviderProxy是供客户端使用的
3.ProviderClientRecord是ActivityThread提供的用于保存ContentProvider信息的一个数据结构。它的mLocalProvider用于保存ContentProvider对象，mProvider用于保存IContentProvider对象。另外一个成员mName用于保持该ContentProvider的一个authority。注意，ContentProvider可以定义多个authority，就好像一个网站有多个域名一样。
public final void publishContentProviders(IApplicationThread caller,
List<ContentProviderHolder> providers) {
if (providers == null) {
return;
} enforceNotIsolatedCaller("publishContentProviders");
synchronized (this) {
final ProcessRecord r = getRecordForAppLocked(caller);
if (DEBUG_MU) Slog.v(TAG_MU, "ProcessRecord uid = " + r.uid);
if (r == null) {
throw new SecurityException(
"Unable to find app for caller " + caller
+ " (pid=" + Binder.getCallingPid()
+ ") when publishing content providers");
} final long origId = Binder.clearCallingIdentity(); final int N = providers.size();
for (int i=0; i<N; i++) {
ContentProviderHolder src = providers.get(i);
if (src == null || src.info == null || src.provider == null) {
continue;
}
ContentProviderRecord dst = r.pubProviders.get(src.info.name);
if (DEBUG_MU) Slog.v(TAG_MU, "ContentProviderRecord uid = " + dst.uid);
if (dst != null) {
ComponentName comp = new ComponentName(dst.info.packageName, dst.info.name);
mProviderMap.putProviderByClass(comp, dst);
String names[] = dst.info.authority.split(";");
for (int j = 0; j < names.length; j++) {
mProviderMap.putProviderByName(names[j], dst);
} int NL = mLaunchingProviders.size();
int j;
for (j=0; j<NL; j++) {
if (mLaunchingProviders.get(j) == dst) {
mLaunchingProviders.remove(j);
j--;
NL--;
}
}
synchronized (dst) {
dst.provider = src.provider;
dst.proc = r;
dst.notifyAll();
}
updateOomAdjLocked(r);
maybeUpdateProviderUsageStatsLocked(r, src.info.packageName,
src.info.authority);
}
} Binder.restoreCallingIdentity(origId);
}
}
瀑布lishContentProviders的工作流程
1.先根据调用者的PID找到对应的ProcessRecord对象
2.该ProcessRecord的pubProviders中保存了ContentProviderRecord信息。该信息由前面介绍的AMS的generateApplicationProvidersLocked函数根据Package本身的信息生成。此处将判断要发布的ContentProvider是否由该Package声明
3.如果判断返回成功，则将该ContentProvider及其对应的authority加到mProvidersByName中。注意，AMS中还有一个mProvidersByClass变量，该变量以ContentProvider的ComponentName为key，即系统提供两种方式找到某一个ContentProvider，一种是通过authority，另一种方式就是指明ComponentName。
4.mLaunchProviders和最后的notifyAll函数用于通知那些等待ContentProvider所在进程启动的客户端进程。例如，进程A要查询一个数据库，需要通过进程B中的某个ContentProvider来实施。如果B还未启动，那么AMS就需要先启动B。在这段时间内，A需要等待B启动并注册对应的ContentProvider。B一旦完成注册，就需要告知A退出等待以继续后续的查询工作。
public void systemReady(final Runnable goingCallback) {
synchronized(this) {
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();
// Check to see if there are any update receivers to run.
if (!mDidUpdate) {
if (mWaitingUpdate) {
return;
}
final ArrayList<ComponentName> doneReceivers = new ArrayList<ComponentName>();
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);
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) {
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);
mUiHandler.sendMessage(msg);
}
}
}
retrieveSettings();
loadResourcesOnSystemReady();
synchronized (this) {
readGrantedUriPermissionsLocked();
}
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 {
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, null /* ABI override */);
}
}
}
} catch (RemoteException ex) {
// pm is in same process, this will never happen.
}
}
// Start up initial activity.
mBooting = true;
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) {
}
if (!Build.isBuildConsistent()) {
Slog.e(TAG, "Build fingerprint is not consistent, warning user");
mUiHandler.obtainMessage(SHOW_FINGERPRINT_ERROR_MSG).sendToTarget();
}
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);
broadcastIntentLocked(null, null, intent,
null, null, 0, null, null, null, AppOpsManager.OP_NONE,
null, 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);
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}, AppOpsManager.OP_NONE,
null, true, false, MY_PID, Process.SYSTEM_UID, UserHandle.USER_ALL);
} catch (Throwable t) {
Slog.wtf(TAG, "Failed sending first user broadcasts", t);
} finally {
Binder.restoreCallingIdentity(ident);
}
mStackSupervisor.resumeTopActivitiesLocked();
sendUserSwitchBroadcastsLocked(-1, mCurrentUserId);
}
}
systemReady三阶段的工作
1.第一阶段：发送并处理与PRE_BOOT_COMPLETED广播相关的事情
2.第二阶段：（1）杀死那些在AMS还未启动完毕就先启动的应用进程。注意，这些进程一定是APK所在的java进程，因为只有应用进程才会向AMS注册，而一般Native（例如mediaserver）进程是不会向AMS注册的
（2）从Setting数据库获取配置信息，目前只取4个配置参数，分别是debug_app(设置需要debug的app的名称)、wait_for_debugger（如果为1，则等待调试器，否则正常启动debug_app）、always_finish_activities（当一个activity不再有地方使用时，是否立即对它执行destroy）、font_scale（用于控制字体放大倍数，这是android4.0新增的功能）。以上配置项由Setting数据库的system表提供
3.第三阶段：（1）调用systemReady设置的回调对象goingCallback的run函数
（2）启动那些声明了persistent的APK
（3）启动桌面
启动Home桌面
final boolean resumeTopActivityLocked(ActivityRecord prev, Bundle options) {
if (mStackSupervisor.inResumeTopActivity) {
// Don't even start recursing.
return false;
}
boolean result = false;
try {
// Protect against recursion.
mStackSupervisor.inResumeTopActivity = true;
if (mService.mLockScreenShown == ActivityManagerService.LOCK_SCREEN_LEAVING) {
mService.mLockScreenShown = ActivityManagerService.LOCK_SCREEN_HIDDEN;
mService.updateSleepIfNeededLocked();
}
result = resumeTopActivityInnerLocked(prev, options);
} finally {
mStackSupervisor.inResumeTopActivity = false;
}
return result;
}
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;
}
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.instrumentationClass == null) {
intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
mStackSupervisor.startHomeActivity(intent, aInfo, reason);
}
}
return true;
}
AMS总结
1.main函数：创建AMS实例，其中最重要的工作是创建android运行环境，得到一个ActivityThread和Context对象
2.AMS的setSystemProcess函数：该函数注册AMS和meminfo等服务到ServiceManager中，另外，它为system_server创建了一个ProcessRecord对象。由于AMS是Java世界的进程管理及调度中心，要做到对java进程一视同仁，尽管system_server贵为系统进程，此时也不得不将其并入AMS的管理范围内
3.AMS的installSystemProviders函数：为system_server加载SettingProvider
4.AMS的systemReady函数：做系统启动完毕前最后一些扫尾工作。该函数调用完毕后，Home Activity将呈现在用户面前
@Override
public final WaitResult startActivityAndWait(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle options, int userId) {
enforceNotIsolatedCaller("startActivityAndWait");
userId = handleIncomingUser(Binder.getCallingPid(), Binder.getCallingUid(), userId,
false, ALLOW_FULL_ONLY, "startActivityAndWait", null);
WaitResult res = new WaitResult();
// TODO: Switch to user app stacks here.
mStackSupervisor.startActivityMayWait(caller, -1, callingPackage, intent, resolvedType,
null, null, resultTo, resultWho, requestCode, startFlags, profilerInfo, res, null,
options, false, userId, null, null);
return res;
}
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