Android知识总结
一、addService流程
二、注册服务
SystemServer服务对照表
SystemServer执行流程
从 SystemServer#main 方法中启动
public static void main(String[] args) {
new SystemServer().run();
}
public SystemServer() {
// Check for factory test mode.
mFactoryTestMode = FactoryTest.getMode();
mStartCount = SystemProperties.getInt(SYSPROP_START_COUNT, 0) + 1;
mRuntimeStartElapsedTime = SystemClock.elapsedRealtime();
mRuntimeStartUptime = SystemClock.uptimeMillis();
Process.setStartTimes(mRuntimeStartElapsedTime, mRuntimeStartUptime);
mRuntimeRestart = "1".equals(SystemProperties.get("sys.boot_completed"));
}
在 SystemServer#run 创建 SystemServiceManager ，并启动服务
private void run() {
TimingsTraceAndSlog t = new TimingsTraceAndSlog();
try {
t.traceBegin("InitBeforeStartServices");
// Record the process start information in sys props.
SystemProperties.set(SYSPROP_START_COUNT, String.valueOf(mStartCount));
SystemProperties.set(SYSPROP_START_ELAPSED, String.valueOf(mRuntimeStartElapsedTime));
SystemProperties.set(SYSPROP_START_UPTIME, String.valueOf(mRuntimeStartUptime));
EventLog.writeEvent(EventLogTags.SYSTEM_SERVER_START,
mStartCount, mRuntimeStartUptime, mRuntimeStartElapsedTime);
// core/jni/AndroidRuntime.cpp
if (!SystemProperties.get("persist.sys.language").isEmpty()) {
final String languageTag = Locale.getDefault().toLanguageTag();
SystemProperties.set("persist.sys.locale", languageTag);
SystemProperties.set("persist.sys.language", "");
SystemProperties.set("persist.sys.country", "");
SystemProperties.set("persist.sys.localevar", "");
}
// The system server should never make non-oneway calls
Binder.setWarnOnBlocking(true);
// The system server should always load safe labels
PackageItemInfo.forceSafeLabels();
// Default to FULL within the system server.
SQLiteGlobal.sDefaultSyncMode = SQLiteGlobal.SYNC_MODE_FULL;
// Deactivate SQLiteCompatibilityWalFlags until settings provider is initialized
SQLiteCompatibilityWalFlags.init(null);
// Here we go!
Slog.i(TAG, "Entered the Android system server!");
final long uptimeMillis = SystemClock.elapsedRealtime();
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN, uptimeMillis);
if (!mRuntimeRestart) {
FrameworkStatsLog.write(FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME_REPORTED,
FrameworkStatsLog
.BOOT_TIME_EVENT_ELAPSED_TIME__EVENT__SYSTEM_SERVER_INIT_START,
uptimeMillis);
}
VMRuntime.getRuntime().clearGrowthLimit();
Environment.setUserRequired(true);
// Within the system server, any incoming Bundles should be defused
// to avoid throwing BadParcelableException.
BaseBundle.setShouldDefuse(true);
// Within the system server, when parceling exceptions, include the stack trace
Parcel.setStackTraceParceling(true);
// Ensure binder calls into the system always run at foreground priority.
BinderInternal.disableBackgroundScheduling(true);
// Increase the number of binder threads in system_server
BinderInternal.setMaxThreads(sMaxBinderThreads);
// Prepare the main looper thread (this thread).
android.os.Process.setThreadPriority(
android.os.Process.THREAD_PRIORITY_FOREGROUND);
android.os.Process.setCanSelfBackground(false);
Looper.prepareMainLooper();
Looper.getMainLooper().setSlowLogThresholdMs(
SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);
SystemServiceRegistry.sEnableServiceNotFoundWtf = true;
//加载本地系统服务库，并进行初始化.
System.loadLibrary("android_servers");
// Allow heap / perf profiling.
initZygoteChildHeapProfiling();
// Debug builds - spawn a thread to monitor for fd leaks.
if (Build.IS_DEBUGGABLE) {
spawnFdLeakCheckThread();
}
// Check whether we failed to shut down last time we tried.
// This call may not return.
performPendingShutdown();
// Initialize the system context.
//创建系统上下文
createSystemContext();
// Call per-process mainline module initialization.
ActivityThread.initializeMainlineModules();
//创建 SystemServiceManager 管理器
//下面的系统服务开启都需要调用 SystemServiceManager.startService(Class)，这个方法通过反射来启动对应的服务
mSystemServiceManager = new SystemServiceManager(mSystemContext);
mSystemServiceManager.setStartInfo(mRuntimeRestart,
mRuntimeStartElapsedTime, mRuntimeStartUptime);
LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
// Prepare the thread pool for init tasks that can be parallelized
SystemServerInitThreadPool.start();
// Attach JVMTI agent if this is a debuggable build and the system property is set.
if (Build.IS_DEBUGGABLE) {
// Property is of the form "library_path=parameters".
String jvmtiAgent = SystemProperties.get("persist.sys.dalvik.jvmtiagent");
if (!jvmtiAgent.isEmpty()) {
int equalIndex = jvmtiAgent.indexOf('=');
String libraryPath = jvmtiAgent.substring(0, equalIndex);
String parameterList =
jvmtiAgent.substring(equalIndex + 1, jvmtiAgent.length());
// Attach the agent.
try {
Debug.attachJvmtiAgent(libraryPath, parameterList, null);
} catch (Exception e) {
Slog.e("System", "*************************************************");
Slog.e("System", "********** Failed to load jvmti plugin: " + jvmtiAgent);
}
}
}
} finally {
t.traceEnd(); // InitBeforeStartServices
}
// Setup the default WTF handler
RuntimeInit.setDefaultApplicationWtfHandler(SystemServer::handleEarlySystemWtf);
// 启动SM管理的服务
try {
t.traceBegin("StartServices");
//引导服务 - AMS
startBootstrapServices(t);
//核心服务 - 系统用到的一些服务
startCoreServices(t);
//其他服务 - WMS
startOtherServices(t);
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
} finally {
t.traceEnd(); // StartServices
}
StrictMode.initVmDefaults(null);
if (!mRuntimeRestart && !isFirstBootOrUpgrade()) {
final long uptimeMillis = SystemClock.elapsedRealtime();
FrameworkStatsLog.write(FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME_REPORTED,
FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME__EVENT__SYSTEM_SERVER_READY,
uptimeMillis);
final long maxUptimeMillis = 60 * 1000;
if (uptimeMillis > maxUptimeMillis) {
Slog.wtf(SYSTEM_SERVER_TIMING_TAG,
"SystemServer init took too long. uptimeMillis=" + uptimeMillis);
}
}
// Loop forever.
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
}
主要步骤
- 1、createSystemContext 创建系统上下文
- 2、创建 SystemServiceManager 系统服务管理器
- 3、startBootstrapServices 引导服务
- 4、startCoreServices 核心服务
- 5、startOtherServices 其他服务
三、createSystemContext 创建系统上下文
private void createSystemContext() {
// 1 获取 ActivityThread
ActivityThread activityThread = ActivityThread.systemMain();
mSystemContext = activityThread.getSystemContext();
mSystemContext.setTheme(DEFAULT_SYSTEM_THEME);
final Context systemUiContext = activityThread.getSystemUiContext();
systemUiContext.setTheme(DEFAULT_SYSTEM_THEME);
}
执行ActivityThread#systemMain方法
@UnsupportedAppUsage
public static ActivityThread systemMain() {.
if (!ActivityManager.isHighEndGfx()) {
ThreadedRenderer.disable(true);
} else {
ThreadedRenderer.enableForegroundTrimming();
}
//创建 ActivityThread
ActivityThread thread = new ActivityThread();
thread.attach(true, 0);
return thread;
}
执行attach绑定操作
@UnsupportedAppUsage
private void attach(boolean system, long startSeq) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) { //非系统服务走这里，即启动我们的 app
android.ddm.DdmHandleAppName.setAppName("",
UserHandle.myUserId());
RuntimeInit.setApplicationObject(mAppThread.asBinder());
final IActivityManager mgr = ActivityManager.getService();
try {
mgr.attachApplication(mAppThread, startSeq);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
// 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 {
ActivityTaskManager.getService().releaseSomeActivities(mAppThread);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
}
});
} else { //系统服务走这里
try {
mInstrumentation = new Instrumentation();
mInstrumentation.basicInit(this);
//创建两个 content ，一个是 system 的content，另一个是 app 的 content
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
//创建application
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
ViewRootImpl.ConfigChangedCallback configChangedCallback
= (Configuration globalConfig) -> {
synchronized (mResourcesManager) {
// TODO (b/135719017): Temporary log for debugging IME service.
if (Build.IS_DEBUGGABLE && mHasImeComponent) {
Log.d(TAG, "ViewRootImpl.ConfigChangedCallback for IME, "
+ "config=" + globalConfig);
}
// We need to apply this change to the resources immediately, because upon returning
// the view hierarchy will be informed about it.
if (mResourcesManager.applyConfigurationToResourcesLocked(globalConfig,
null /* compat */,
mInitialApplication.getResources().getDisplayAdjustments())) {
updateLocaleListFromAppContext(mInitialApplication.getApplicationContext(),
mResourcesManager.getConfiguration().getLocales());
// This actually changed the resources! Tell everyone about it.
if (mPendingConfiguration == null
|| mPendingConfiguration.isOtherSeqNewer(globalConfig)) {
mPendingConfiguration = globalConfig;
sendMessage(H.CONFIGURATION_CHANGED, globalConfig);
}
}
}
};
ViewRootImpl.addConfigCallback(configChangedCallback);
}
- 执行步骤
- 1、当 system == false时，走启动我们 app 的服务
- 2、当 system == true时，走系统服务。会创建一个system的content；和一个app的content
3.1、创建系统上下文
public ContextImpl getSystemContext() {
synchronized (this) {
if (mSystemContext == null) {
//创建system的content
mSystemContext = ContextImpl.createSystemContext(this);
}
return mSystemContext;
}
}
进入ContextImpl#createSystemContext方法
@UnsupportedAppUsage
static ContextImpl createSystemContext(ActivityThread mainThread) {
//创建 LoadedApk，一个app对应一个LoadedApk
LoadedApk packageInfo = new LoadedApk(mainThread);
//创建 ContextImpl
ContextImpl context = new ContextImpl(null, mainThread, packageInfo, null, null, null, null,
0, null, null);
context.setResources(packageInfo.getResources());
context.mResources.updateConfiguration(context.mResourcesManager.getConfiguration(),
context.mResourcesManager.getDisplayMetrics());
context.mIsSystemOrSystemUiContext = true;
return context;
}
3.2、创建app上下文
执行ContextImpl#createAppContext方法
static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo) {
return createAppContext(mainThread, packageInfo, null);
}
static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo,
String opPackageName) {
if (packageInfo == null) throw new IllegalArgumentException("packageInfo");
//创建当前app的Context
ContextImpl context = new ContextImpl(null, mainThread, packageInfo, null, null, null, null,
0, null, opPackageName);
context.setResources(packageInfo.getResources());
context.mIsSystemOrSystemUiContext = isSystemOrSystemUI(context);
return context;
}
3.2、创建 application
执行LoadedApk#makeApplication方法
@UnsupportedAppUsage
public Application makeApplication(boolean forceDefaultAppClass,
Instrumentation instrumentation) {
if (mApplication != null) {
return mApplication;
}
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "makeApplication");
Application app = null;
String appClass = mApplicationInfo.className;
if (forceDefaultAppClass || (appClass == null)) {
appClass = "android.app.Application";
}
try {
final java.lang.ClassLoader cl = getClassLoader();
if (!mPackageName.equals("android")) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER,
"initializeJavaContextClassLoader");
initializeJavaContextClassLoader();
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
}
// Rewrite the R 'constants' for all library apks.
SparseArray packageIdentifiers = getAssets().getAssignedPackageIdentifiers(
false, false);
for (int i = 0, n = packageIdentifiers.size(); i < n; i++) {
final int id = packageIdentifiers.keyAt(i);
if (id == 0x01 || id == 0x7f) {
continue;
}
rewriteRValues(cl, packageIdentifiers.valueAt(i), id);
}
ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);
NetworkSecurityConfigProvider.handleNewApplication(appContext);
//通过反射创建app
app = mActivityThread.mInstrumentation.newApplication(
cl, appClass, appContext);
appContext.setOuterContext(app);
} catch (Exception e) {
if (!mActivityThread.mInstrumentation.onException(app, e)) {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
throw new RuntimeException(
"Unable to instantiate application " + appClass
+ ": " + e.toString(), e);
}
}
mActivityThread.mAllApplications.add(app);
mApplication = app;
if (instrumentation != null) {
//system 层不会进入，因为传入的 instrumentation == null
try {
instrumentation.callApplicationOnCreate(app);
} catch (Exception e) {
if (!instrumentation.onException(app, e)) {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
throw new RuntimeException(
"Unable to create application " + app.getClass().getName()
+ ": " + e.toString(), e);
}
}
}
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
return app;
}
执行Instrumentation#newApplication的方法
public Application newApplication(ClassLoader cl, String className, Context context)
throws InstantiationException, IllegalAccessException,
ClassNotFoundException {
Application app = getFactory(context.getPackageName())
.instantiateApplication(cl, className);//里面通过反射实现
app.attach(context);
return app;
}
进入AppComponentFactory中，进行反射创建Application
public @NonNull Application instantiateApplication(@NonNull ClassLoader cl,
@NonNull String className)
throws InstantiationException, IllegalAccessException, ClassNotFoundException {
return (Application) cl.loadClass(className).newInstance();
}
四、创建系统服务管理器
SystemServiceManager.java
SystemServiceManager(Context context) {
mContext = context;
}
这里简单介绍下服务的启动过程：
public SystemService startService(String className) {
//获取服务的名称
final Class serviceClass = loadClassFromLoader(className,
this.getClass().getClassLoader());
//启动服务
return startService(serviceClass);
}
4.1、获取服务的名称
private static Class loadClassFromLoader(String className,
ClassLoader classLoader) {
try {
//通过反射获取
return (Class) Class.forName(className, true, classLoader);
} catch (ClassNotFoundException ex) {
throw new RuntimeException("Failed to create service " + className
+ " from class loader " + classLoader.toString() + ": service class not "
+ "found, usually indicates that the caller should "
+ "have called PackageManager.hasSystemFeature() to check whether the "
+ "feature is available on this device before trying to start the "
+ "services that implement it. Also ensure that the correct path for the "
+ "classloader is supplied, if applicable.", ex);
}
}
4.2、启动服务
public T startService(Class serviceClass) {
try {
final String name = serviceClass.getName();
Slog.i(TAG, "Starting " + name);
Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartService " + name);
// Create the service.
if (!SystemService.class.isAssignableFrom(serviceClass)) {
throw new RuntimeException("Failed to create " + name
+ ": service must extend " + SystemService.class.getName());
}
final T service;
try {
//获取构造方法
Constructor constructor = serviceClass.getConstructor(Context.class);
//执行构造方法
service = constructor.newInstance(mContext);
} catch (InstantiationException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service could not be instantiated", ex);
} catch (IllegalAccessException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (NoSuchMethodException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service must have a public constructor with a Context argument", ex);
} catch (InvocationTargetException ex) {
throw new RuntimeException("Failed to create service " + name
+ ": service constructor threw an exception", ex);
}
//启动服务
startService(service);
return service;
} finally {
Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
}
}
public void startService(@NonNull final SystemService service) {
// Register it.
mServices.add(service);
// Start it.
long time = SystemClock.elapsedRealtime();
try {
//启动，执行服务的 onStart 方法
service.onStart();
} catch (RuntimeException ex) {
throw new RuntimeException("Failed to start service " + service.getClass().getName()
+ ": onStart threw an exception", ex);
}
warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onStart");
}
SystemServiceManager 和 ServiceManager的区别
- SystemServiceManager ：它会对系统的服务进行创建、启动和生命周期管理。
- ServiceManager：管理Binder服务的