if（"start-system-server".equals（argv[i]））{
startSystemServer=true;
}elseif（argv[i].startsWith（ABI_LIST_ARG））{
abiList=argv[i].substring（ABI_LIST_ARG.length（））;
}elseif（argv[i].startsWith（SOCKET_NAME_ARG））{
socketName=argv[i].substring（SOCKET_NAME_ARG.length（））;
}else{
thrownewRuntimeException（"Unknowncommandlineargument:
"+argv[i]）;
}
}
.....
//预加载android依赖的文件
preload（）;
.....
if（startSystemServer）{
//启动系统服务
startSystemServer（abiList,socketName）;
}
.....
}catch（MethodAndArgsCallercaller）{
caller.run（）;
}catch（Throwableex）{
Log.e（TAG,"Zygotediedwithexception",ex）;
closeServerSocket（）;
throwex;
}
}
看这个类的main方法，最上面根据传入的参数判断是否将startSystemServer这个标记设为true，接着预加载android依赖的文件，最后根据上面设置的标记来判断是否能启动系统服务。
接着看ZygoteInit.java中main方法在最后调用startSystemServer方法具体内容
privatestaticbooleanstartSystemServer（StringabiList,StringsocketName）
throwsMethodAndArgsCaller,RuntimeException{
.....
/*Hardcodedcommandlinetostartthesystemserver*/
Stringargs[]={
"--setuid=1000",
"--setgid=1000",
"--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1032,3001,3002,3003,3006,3007,3009,3010",
"--capabilities="+capabilities+","+capabilities,
"--nice-name=system_server",
"--runtime-args",
"com.android.server.SystemServer",
};
.....
try{
parsedArgs=newZygoteConnection.Arguments（args）;
ZygoteConnection.applyDebuggerSystemProperty（parsedArgs）;
ZygoteConnection.applyInvokeWithSystemProperty（parsedArgs）;
//Zygote进程开始fork子进程，启动SystemServer
/*Requesttoforkthesystemserverprocess*/
pid=Zygote.forkSystemServer（
parsedArgs.uid,parsedArgs.gid,
parsedArgs.gids,
parsedArgs.debugFlags,
null,
parsedArgs.permittedCapabilities,
parsedArgs.effectiveCapabilities）;
}catch（IllegalArgumentExceptionex）{
thrownewRuntimeException（ex）;
}
.....
}
SystemServer.java代码
/frameworks/base/services/java/com/android/server/SystemServer.java
/**
*Themainentrypointfromzygote.
*/
publicstaticvoidmain（String[]args）{
newSystemServer（）.run（）;
}
privatevoidrun（）{
......
//Startservices.
try{
Trace.traceBegin（Trace.TRACE_TAG_SYSTEM_SERVER,"StartServices"）;
startBootstrapServices（）;
//启动核心Service
startCoreServices（）;
//启动其他Service
startOtherServices（）;
}catch（Throwableex）{
Slog.e（"System","******************************************"）;
Slog.e（"System","************Failurestartingsystemservices",ex）;
throwex;
}finally{
Trace.traceEnd（Trace.TRACE_TAG_SYSTEM_SERVER）;
}
//Loopforever.
Looper.loop（）;
thrownewRuntimeException（"Mainthreadloopunexpectedlyexited"）;
}
启动SystemServer.java的startOtherServices方法
/**
*Startsamiscellaneousgrabbagofstuffthathasyettoberefactored
*andorganized.
*/
privatevoidstartOtherServices（）{
.....
//Wenowtelltheactivitymanageritisokaytorunthirdparty
//code.Itwillcallbackintousonceithasgottentothestate
//wherethirdpartycodecanreallyrun（butbeforeithasactually
//startedlaunchingtheinitialapplications）,forustocompleteour
//initialization.
mActivityManagerService.systemReady（newRunnable（）{
@Override
publicvoidrun（）{
Slog.i（TAG,"Makingservicesready"）;
.....
}
}
.....
}
ActivityManagerService.java中的mStackSupervisor.resumeFocusedStackTopActivityLocked（）
publicvoidsystemReady（finalRunnablegoingCallback）{
.....
Slog.i（TAG,"Systemnowready"）;
EventLog.writeEvent（EventLogTags.BOOT_PROGRESS_AMS_READY,
SystemClock.uptimeMillis（））;
.....
synchronized（this）{
//Onlystartupencryption-awarepersistentapps;onceuseris
//unlockedwe'llcomebackaroundandstartunawareapps
startPersistentApps（PackageManager.MATCH_DIRECT_BOOT_AWARE）;
.....
//调用ActivityStackSupervisor中的resumeFocusedStackTopActivityLocked方法
mStackSupervisor.resumeFocusedStackTopActivityLocked（）;
mUserController.sendUserSwitchBroadcastsLocked（-1,currentUserId）;
}
}
ActivityStackSupervisor.java中的resumeFocusedStackTopActivityLocked方法
booleanresumeFocusedStackTopActivityLocked（）{
returnresumeFocusedStackTopActivityLocked（null,null,null）;
}
booleanresumeFocusedStackTopActivityLocked（
ActivityStacktargetStack,ActivityRecordtarget,ActivityOptionstargetOptions）{
if（targetStack!
=ull&&isFocusedStack（targetStack））{
returntargetStack.resumeTopActivityUncheckedLocked（target,targetOptions）;
}
finalActivityRecordr=mFocusedStack.topRunningActivityLocked（）;
if（r==null||r.state!
=RESUMED）{
//调用ActivityStack中的resumeTopActivityUncheckedLocked来保证栈中的顶层Activity被重新启动
mFocusedStack.resumeTopActivityUncheckedLocked（null,null）;
}
returnfalse;
}
ActivityStack.java中的resumeTopActivityUncheckedLocked方法
booleanresumeTopActivityUncheckedLocked（ActivityRecordprev,ActivityOptionsoptions）{
....
booleanresult=false;
try{
//Protectagainstrecursion.
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;
}
returnresult;
}
privatebooleanresumeTopActivityInnerLocked（ActivityRecordprev,ActivityOptionsoptions）{
if（DEBUG_LOCKSCREEN）mService.logLockScreen（""）;
if（!
mService.mBooting&&!
mService.mBooted）{
//Notreadyyet!
returnfalse;
}
.....
if（next==null）{
//Therearenomoreactivities!
finalStringreason="noMoreActivities";
finalintreturnTaskType=prevTask==null||!
prevTask.isOverHomeStack（）
?
HOME_ACTIVITY_TYPE:
prevTask.getTaskToReturnTo（）;
if（!
mFullscreen&&adjustFocusToNextFocusableStackLocked（returnTaskType,reason））{
//Trytomovefocustothenextvisiblestackwitharunningactivityifthis
//stackisnotcoveringtheentirescreen.
returnmStackSupervisor.resumeFocusedStackTopActivityLocked（
mStackSupervisor.getFocusedStack（）,prev,null）;
}
//Let'sjuststartuptheL
升级会员 