网站用词精准性,营口网站建设价格,昌黎县城乡建设局网站,网页游戏梦幻西游前言
看过源码的都知道#xff0c;Launcher系统启动都会经过这三个进程 init -zygote - system_server。今天我们就来讲解一下这三个进程以及Launcher系统启动。
init进程
准备Android虚拟机环境#xff1a;创建和挂载系统文件目录#xff1b;初始化属性服务Launcher系统启动都会经过这三个进程 init -zygote - system_server。今天我们就来讲解一下这三个进程以及Launcher系统启动。
init进程
准备Android虚拟机环境创建和挂载系统文件目录初始化属性服务设置子进程信号处理函数防止init的子进程出现僵尸进程在子进程暂停和结束是接受信号并进行处理 僵尸进程父进程使用fork创建子进程如果子进程终止但父进程并不知道已经终止。虽然此时子进程已经退出但是还是保留了他的信息进程号。退出状态。运行时间等。这样系统进程表就会被无端耗用如果耗尽之后系统可能就无法再创建新的进程。 启动属性服务并为其分配内存用来存储属性使用一个键值对注册表记录用户\软件的一些使用信息确保系统或者软件重启之后能根据注册表中的信息进行初始化的工作解析init.rc配置文件。 解析init.zygote脚本文件启动zygote进程
总的来说做了三件事
创建和挂在系统启动所需要的文件目录初始化和启动属性服务解析init.rc配置文件并启动zygote进程。
zygote进程
init通过调用app_main.cpp的main函数中的start方法来启动zygote进程。 DVMART应用程序进程以及SystemServer进程都是有zygote创建。通过fork自身从zygote进程来创建新的应用进程。因此zygote进程和它的子进程都会运行main函数。main函数里会通过标记查看main函数是运行在zygote进程还是子进程。如果实在zygote进程里那么就会调用AppRuntime的start函数。在start函数里会创建Java虚拟机以及做一些其他的准备工作。最后通过JNI调用ZygoteInit.java里的mian方法进入Java框架层。
main方法主要做下面几件事情
创建一个Server端的Socket用来等待AMS请求创建新的应用进程预加载类和资源启动SystemServer进程等待AMS请求创建新的应用程序进程通过无限循环while(true)等待AMS的请求。
SystemServerzygote第一个启动的进程
SystemServer主要用来创建系统服务例如AMSWMS都是有他创建的。Zygote进程通过forkSystemServetr方法复制Zygote进程的地址空间并关闭SystemServer不需要的Socket进程。然后通过handleSystemServerProcess方法启动进程。
//ZygoteInit.java
private static Runnable forkSystemServer(String abiList, String socketName,ZygoteServer zygoteServer) {String[] args {--setuid1000,--setgid1000,--setgroups1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1023, 1024,1032,1065,3001,3002,3003,3006,3007,3009,3010,3011,3012,--capabilities capabilities , capabilities,--nice-namesystem_server,--runtime-args,--target-sdk-version VMRuntime.SDK_VERSION_CUR_DEVELOPMENT,com.android.server.SystemServer,};ZygoteArguments parsedArgs;try {ZygoteCommandBuffer commandBuffer new ZygoteCommandBuffer(args);try {parsedArgs ZygoteArguments.getInstance(commandBuffer);} catch (EOFException e) {throw new AssertionError(Unexpected argument error for forking system server, e);}catch (IllegalArgumentException e) {} int pid;try {//.../* Request to fork the system server process */pid Zygote.forkSystemServer(parsedArgs.mUid, parsedArgs.mGid,parsedArgs.mGids,parsedArgs.mRuntimeFlags,null,parsedArgs.mPermittedCapabilities,parsedArgs.mEffectiveCapabilities);} catch (IllegalArgumentException ex) {throw new RuntimeException(ex);}if (pid 0) {if (hasSecondZygote(abiList)) {waitForSecondaryZygote(socketName);}//关闭Zygote进程创建的SocketzygoteServer.closeServerSocket();return handleSystemServerProcess(parsedArgs);}return null;}
在handleSystemServerProcess方法中会启动Binder线程池这样SystemServer就可以使用Binder和其他应用进程进程通讯。
//ZygoteInit.javaprivate static Runnable handleSystemServerProcess(ZygoteArguments parsedArgs) {///if (parsedArgs.mInvokeWith ! null) {//} else {return ZygoteInit.zygoteInit(parsedArgs.mTargetSdkVersion,parsedArgs.mDisabledCompatChanges,parsedArgs.mRemainingArgs, cl);}}
//ZygoteInit.javaprivate static Runnable handleSystemServerProcess(ZygoteArguments parsedArgs) {///if (parsedArgs.mInvokeWith ! null) {//} else {return ZygoteInit.zygoteInit(parsedArgs.mTargetSdkVersion,parsedArgs.mDisabledCompatChanges,parsedArgs.mRemainingArgs, cl);}}
启动Binder线程池之后会调用RuntimeInit.applicationInit
//RuntimeInit.javaprotected static Runnable applicationInit(int targetSdkVersion, long[] disabledCompatChanges,String[] argv, ClassLoader classLoader) {//final Arguments args new Arguments(argv);return findStaticMain(args.startClass, args.startArgs, classLoader);}
然后调用findStaticMain 方法 RuntimeInit.javaprotected static Runnable findStaticMain(String className, String[] argv,ClassLoader classLoader) {Class? cl;try {//使用反射创建SystemServer。cl Class.forName(className, true, classLoader);} catch (ClassNotFoundException ex) {throw new RuntimeException(Missing class when invoking static main className,ex);}Method m;try {//找到ServerServer的main方法m cl.getMethod(main, new Class[] { String[].class });} catch (NoSuchMethodException ex) {throw new RuntimeException(Missing static main on className, ex);} catch (SecurityException ex) {throw new RuntimeException(Problem getting static main on className, ex);}int modifiers m.getModifiers();if (! (Modifier.isStatic(modifiers) Modifier.isPublic(modifiers))) {throw new RuntimeException(Main method is not public and static on className);}//通过MethodAndArgsCaller调用SystemServer的main方法return new MethodAndArgsCaller(m, argv);}可以看到这里使用反射的方式创建了Systemserver其中的className实在ZygoteInit.java类中forkSystemServer 方法的变量arg中初始化的。然后通过MethodAndArgsCaller来调用Systemserver的main方法主要是为了能让ZygoteInit.mian能捕获异常因为SystemServer的main方法在调用之前SystemServer进程已经做了很多准备工作而如果慧姐抛出异常则会清理掉所有的堆栈信帧使得SystemServer的main看起来就不是SystemServer的入口方法了MethodAndArgsCaller代码也很简单
static class MethodAndArgsCaller implements Runnable {/** method to call */private final Method mMethod;/** argument array */private final String[] mArgs;public MethodAndArgsCaller(Method method, String[] args) {mMethod method;mArgs args;}public void run() {try {mMethod.invoke(null, new Object[] { mArgs });} catch (IllegalAccessException ex) {throw new RuntimeException(ex);} catch (InvocationTargetException ex) {Throwable cause ex.getCause();if (cause instanceof RuntimeException) {throw (RuntimeException) cause;} else if (cause instanceof Error) {throw (Error) cause;}throw new RuntimeException(ex);}}}
而在ZygoteInit的main方法中有该异常的捕获的try语句。
在SystemServer中main方法的关键操作如下 public static void main(String[] args) {new SystemServer().run();
}private void run() {//try {Looper.prepareMainLooper();Looper.getMainLooper().setSlowLogThresholdMs(SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);System.loadLibrary(android_servers); createSystemContext(); }//// Start services.try {t.traceBegin(StartServices);startBootstrapServices(t);//启动引导服务startCoreServices(t);//启动核心服务startOtherServices(t);//启动其他服务} catch (Throwable ex) {throw ex;} finally {t.traceEnd(); // StartServices}Looper.loop();
}
SystemServer会创建消息Looper加载库文件并创建系统的Context。然后创建和启动各种系统服务
引导服务Installer、AMS、PMS等核心服务DropBoxManagerService、BatteryService等其他服务CameraService、WMS等
以PowerStatsService为例通过SystemServiceManager的startService方法启动mSystemServiceManager.startService(PowerStatsService.class);
SystemServiceManager:Manages creating, starting, and other lifecycle events of SystemService system services //SystemServiceManager.javaprivate final ArrayListSystemService mServices new ArrayListSystemService();public T extends SystemService T startService(ClassT serviceClass) {try {final String name serviceClass.getName();final T service;try {ConstructorT constructor serviceClass.getConstructor(Context.class);service constructor.newInstance(mContext);} catch (InvocationTargetException ex) {throw new RuntimeException(Failed to create service name : service constructor threw an exception, ex);}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 {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);}
通过创建service然后将service添加到一个ArrayList中这样就完成了注册工作。最后调用service的start方法启动。
SystemServer进程被创建后做了一下工作
启动Binder线程池用于和其他进程通讯创建SystemServerManager用于系统服务的创建、启动和管理使用SystemServerManager启动各种服务。
负责拉起AMS等80多个服务 try {traceBeginAndSlog(StartServices);startBootstrapServices();startCoreServices();startOtherServices();SystemServerInitThreadPool.shutdown();} catch (Throwable ex) {Slog.e(System, ******************************************);Slog.e(System, ************ Failure starting system services, ex);throw ex;} finally {traceEnd();} finishBooting负责发送系统启动完成广播
为什么应用启动时要从zygote进程中fork 若从init fork需要准备虚拟机预加载类文件若从system_server App进程不需要大量的服务AMS WMS PMS等80多种服务
Launcher启动
系统启动的最后一步是启动一个用来显示系统中已安装应用的应用程序——Launcher。通俗的讲它就是Android的系统桌面主要有以下两个特点
作为Android系统的启动器用于启动应用程序作为Android系统的桌面用于显示和管理应用程序的快捷图标或者其他桌面组件。
在SystemServer启动过程中由它启动的AmsActivityManagerService.会将Launcher启动。Launcher的启动入口在SystemServer的startOtherServices方法中
//SystemServer.java
// We now tell the activity manager it is okay to run third party
// code. It will call back into us once it has gotten to the state
// where third party code can really run (but before it has actually
// started launching the initial applications), for us to complete our
// initialization.mActivityManagerService.systemReady(() - {mSystemServiceManager.startBootPhase(t, SystemService.PHASE_ACTIVITY_MANAGER_READY);});根据官方注释我们可以看出在这里系统服务已经就绪到这里系统就算启动完成可以跑第三方的代码了。此时会调用AMS的systemReady方法让AMS去启动Launcher。下面是ActivityManagerService.java中systemReady方法启动Launcher的关键代码
public ActivityTaskManagerInternal mAtmInternal;public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) {synchronized (this) {mAtmInternal.startHomeOnAllDisplays(currentUserId, systemReady);}
} 其中mAtmInternal 的具体实现是ActivityTaskManagerService.LocalService。是在ActivityTaskManagerService里的一个内部类。ActivityTaskManagerService.LocalService.startHomeOnAllDisplays代码如下
Override
public boolean startHomeOnAllDisplays(int userId, String reason) {synchronized (mGlobalLock) {return mRootActivityContainer.startHomeOnAllDisplays(userId, reason);}
}RootActivityContainer.startHomeOnAllDisplays的代码如下
boolean startHomeOnAllDisplays(int userId, String reason) {boolean homeStarted false;// 由于Android系统支持多用户和多显示调用startHomeOnAllDisplays启动每个display上的Home Activityfor (int i mActivityDisplays.size() - 1; i 0; i--) {final int displayId mActivityDisplays.get(i).mDisplayId;homeStarted | startHomeOnDisplay(userId, reason, displayId);}return homeStarted;
}继续追踪startHomeOnDisplay方法
boolean startHomeOnDisplay(int userId, String reason, int displayId) {return startHomeOnDisplay(userId, reason, displayId, false /* allowInstrumenting */,false /* fromHomeKey */);
}boolean startHomeOnDisplay(int userId, String reason, int displayId, boolean allowInstrumenting,boolean fromHomeKey) {if (displayId INVALID_DISPLAY) {displayId getTopDisplayFocusedStack().mDisplayId;}Intent homeIntent null;ActivityInfo aInfo null;if (displayId DEFAULT_DISPLAY) {//第一步获取Intent//这里的mService就是ActivityTaskManagerServicehomeIntent mService.getHomeIntent();aInfo resolveHomeActivity(userId, homeIntent);} else if (shouldPlaceSecondaryHomeOnDisplay(displayId)) {PairActivityInfo, Intent info resolveSecondaryHomeActivity(userId, displayId);aInfo info.first;homeIntent info.second;}if (aInfo null || homeIntent null) {return false;}if (!canStartHomeOnDisplay(aInfo, displayId, allowInstrumenting)) {return false;}homeIntent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name));homeIntent.setFlags(homeIntent.getFlags() | FLAG_ACTIVITY_NEW_TASK);if (fromHomeKey) {homeIntent.putExtra(WindowManagerPolicy.EXTRA_FROM_HOME_KEY, true);}final String myReason reason : userId : UserHandle.getUserId(aInfo.applicationInfo.uid) : displayId;// 第二步启动 mService.getActivityStartController().startHomeActivity(homeIntent, aInfo, myReason,displayId);return true;
}其中第一步获取Intent的getHomeIntent方法在ActivityTaskManagerService中代码如下就是给Intent添加了Intent.CATEGORY_HOME属性
String mTopAction Intent.ACTION_MAIN;Intent getHomeIntent() {Intent intent new Intent(mTopAction, mTopData ! null ? Uri.parse(mTopData) : null);intent.setComponent(mTopComponent);intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);if (mFactoryTest ! FactoryTest.FACTORY_TEST_LOW_LEVEL) {//返回一个Category为Intent.CATEGORY_HOME的Intentintent.addCategory(Intent.CATEGORY_HOME);}return intent;}接下来第二步startHomeActivity方法在ActivityStartController中关键代码入下
void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason, int displayId) {final ActivityOptions options ActivityOptions.makeBasic();options.setLaunchWindowingMode(WINDOWING_MODE_FULLSCREEN);if (!ActivityRecord.isResolverActivity(aInfo.name)) { options.setLaunchActivityType(ACTIVITY_TYPE_HOME);}options.setLaunchDisplayId(displayId);mLastHomeActivityStartResult obtainStarter(intent, startHomeActivity: reason).setOutActivity(tmpOutRecord).setCallingUid(0).setActivityInfo(aInfo).setActivityOptions(options.toBundle()).execute();//启动
}
其中最后的execute最终是执行的ActivityStarter的execute代码 /*** Starts an activity based on the request parameters provided earlier.* return The starter result.*/int execute() {try {// TODO(b/64750076): Look into passing request directly to these methods to allow// for transactional diffs and preprocessing.if (mRequest.mayWait) {return startActivityMayWait(mRequest.caller, mRequest.callingUid,mRequest.callingPackage, mRequest.realCallingPid, mRequest.realCallingUid,mRequest.intent, mRequest.resolvedType,mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,mRequest.resultWho, mRequest.requestCode, mRequest.startFlags,mRequest.profilerInfo, mRequest.waitResult, mRequest.globalConfig,mRequest.activityOptions, mRequest.ignoreTargetSecurity, mRequest.userId,mRequest.inTask, mRequest.reason,mRequest.allowPendingRemoteAnimationRegistryLookup,mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart);} else {return startActivity(mRequest.caller, mRequest.intent, mRequest.ephemeralIntent,mRequest.resolvedType, mRequest.activityInfo, mRequest.resolveInfo,mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,mRequest.resultWho, mRequest.requestCode, mRequest.callingPid,mRequest.callingUid, mRequest.callingPackage, mRequest.realCallingPid,mRequest.realCallingUid, mRequest.startFlags, mRequest.activityOptions,mRequest.ignoreTargetSecurity, mRequest.componentSpecified,mRequest.outActivity, mRequest.inTask, mRequest.reason,mRequest.allowPendingRemoteAnimationRegistryLookup,mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart);}} finally {onExecutionComplete();}}其中startActivity有三个的重载方法经过不断的调用最后会调用startActivity(final ActivityRecord r, ActivityRecord sourceRecord, IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor, int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask, ActivityRecord[] outActivity, boolean restrictedBgActivity) 方法 private int startActivity(final ActivityRecord r, ActivityRecord sourceRecord,IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask,ActivityRecord[] outActivity, boolean restrictedBgActivity) {try {mService.mWindowManager.deferSurfaceLayout();result startActivityUnchecked(r, sourceRecord, voiceSession, voiceInteractor,startFlags, doResume, options, inTask, outActivity, restrictedBgActivity);} }大致的流程图如下
接下来就是Launcher进程和Activity的创建了这个过程和普通的应用启动就没什么区别了详情查看Android Activity的创建流程。
