SystemServer创建：
流程：
->ZygoteInit.java: startSystemServer
->Zygote.java:forkSystemServer
->通过JNI调用native函数,nativeForkSystemServer
上面的步骤就起来了SystemServer进程，后面跟 zygote进程分道扬镳；
SystemServer创建成功后，通过handleSystemServerProcess来进行处理
ZygoteInit.java
if (pid == 0) {
zygoteServer.closeServerSocket();
handleSystemServerProcess(parsedArgs); //通过handleSystemServer来处理
}
private static void handleSystemServerProcess(ZygoteConnection.Arguments parsedArgs){
//调用到ZygoteInit的 zygoteInit.
ZygoteInit.zygoteInit(parsedArgs.targetSdkVersion, parsedArgs.remainingArgs, cl);
}
public static final void zygoteInit(int targetSdkVersion, String[] argv,
ClassLoader classLoader) throws Zygote.MethodAndArgsCaller {
RuntimeInit.commonInit(); // (1) 做一些常规的初始化,这里不做细化
ZygoteInit.nativeZygoteInit(); // (2) 调用native函数
RuntimeInit.applicationInit(targetSdkVersion, argv, classLoader);//(3)在这里会调用到sytemserver的main函数入口
}
这边着重看下(1)nativeZygoteInit函数，这个函数实现在 AndroidRuntime.cpp中：
static void com_android_internal_os_ZygoteInit_nativeZygoteInit(JNIEnv* env, jobject clazz)
{
gCurRuntime->onZygoteInit();
}
gCurRuntime的定义:static AndroidRuntime* gCurRuntime = NULL;
onZygoteInit实现在 AndroidRuntime的子类AppRuntime中， Appruntime定义在app_main.c中
virtual void onZygoteInit()
{
sp<ProcessState> proc = ProcessState::self();
ALOGV("App process: starting thread pool.\n");
proc->startThreadPool(); //启动线程，用于 Binder通信
}
接下来看下(2) Runtimeinit.applicationInit这个函数
protected static void applicationInit(int targetSdkVersion, String[] argv, ClassLoader classLoader)
throws Zygote.MethodAndArgsCaller {
//这边执行到systemServer的main函数
invokeStaticMain(args.startClass, args.startArgs, classLoader);
}
看下invokeStaticMain函数~
private static void invokeStaticMain(String className, String[] argv, ClassLoader classLoader)
throws Zygote.MethodAndArgsCaller {
//这里居然抛出一个异常，全局搜索下，看那边catch这个异常
throw new Zygote.MethodAndArgsCaller(m, argv);
}
全局搜索，发现在ZygoteInit->main里面catch了“Zygote.MethodAndArgsCaller”：
public static void main(String argv[]) {
catch (Zygote.MethodAndArgsCaller caller) {
caller.run();//居然又回调到Zygote.MethodAndArgsCaller的run,醉了
}
}
上述为什么要用异常捕获，而不是直接调用？
继续跟踪：
Zygote.MethodAndArgsCaller
MethodAndArgsCaller是Zygote类的内部类：
public static class MethodAndArgsCaller extends Exception{
public void run() {
try {
mMethod.invoke(null, new Object[] { mArgs }); //反射调用，取到 SystemServer.main
}
}
}
截止到上面， 还只是创建SystemServer,真正开始SystemServer是从调用 main函数开始：
-> 调用SystemServer的main函数
public static void main(String[] args) {
new SystemServer().run();
}
->SystemServer().run()
这里主要是启动一些服务~
private void run() {
//加载 android_servers库
System.loadLibrary("android_servers");
//创建上下文关系
createSystemContext();
// Create the system service manager. ->创建service manager
mSystemServiceManager = new SystemServiceManager(mSystemContext);
mSystemServiceManager.setRuntimeRestarted(mRuntimeRestart);
LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
//开启services
startBootstrapServices();
startCoreServices();
startOtherServices();
}
依次来看下开启的几个服务
startBootstrapServices
private void startBootstrapServices() {
//启动ActivityManagerService
mActivityManagerService = mSystemServiceManager.startService(
ActivityManagerService.Lifecycle.class).getService();
//启动PowerManagerService
mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);
//启动PackageMangerService
mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
//启动SensorService
startSensorService();
}
startCoreServices();
private void startCoreServices() {
// Tracks the battery level. Requires LightService.
mSystemServiceManager.startService(BatteryService.class);
// Tracks application usage stats.
mSystemServiceManager.startService(UsageStatsService.class);
mActivityManagerService.setUsageStatsManager(
LocalServices.getService(UsageStatsManagerInternal.class));
// Tracks whether the updatable WebView is in a ready state and watches for update installs.
mWebViewUpdateService = mSystemServiceManager.startService(WebViewUpdateService.class);
}
startOtherServices->省略掉，反正就是开启services
