1 注册ActivityManagerService

SystemServer执行main方法，接着执行run,在run中有这样一段

frameworks/base/services/java/com/android/server/SystemServer.java

private void run() {            startBootstrapServices();            startCoreServices();            startOtherServices();}复制代码

其中的startBootstrapServices方法去调用startService启动ActivityManagerService。

frameworks/base/services/java/com/android/server/SystemServer.java

private void startBootstrapServices() {// Activity manager runs the show.        mActivityManagerService = mSystemServiceManager.startService(                ActivityManagerService.Lifecycle.class).getService();        ...        // Set up the Application instance for the system process and get started.        mActivityManagerService.setSystemProcess();}复制代码

startService会回调Lifecycle.onStart()，这时已经创建好ActivityManagerService对象mActivityManagerService，然后在SystemServer的startBootstrapServices中继续调用ActivityManagerService的setSystemProcess，

在ServiceManager中完成注册ActivityManagerService。 frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

public void setSystemProcess() {         ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);}复制代码

至此ActivityManagerService完成了初始化。

2 遍历persistent进程

SystemServer执行startBootstrapServices完成AMS的初始化后，继续调用startOtherServices。 frameworks/base/services/java/com/android/server/SystemServer.java

private void startOtherServices() {     mActivityManagerService.systemReady(new Runnable() ...}复制代码

在ActivityManagerService.systemReady中遍历所有persistent进程。 frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

public void systemReady(final Runnable goingCallback) {    ...            synchronized (this) {            if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) {                try {//遍历所有android:persistent属性为true的进程,PhoneApp的persistent也为true                    List apps = AppGlobals.getPackageManager().                        getPersistentApplications(STOCK_PM_FLAGS);                    if (apps != null) {                        int N = apps.size();                        int i;                        for (i=0; iif (info != null &&                                    !info.packageName.equals("android")) {                                addAppLocked(info, false, null /* ABI override */);//persistent进程启动，Phone进程也不例外                            }                        }                    }                } catch (RemoteException ex) {                    // pm is in same process, this will never happen.                }            }            // Start up initial activity.            mBooting = true;            startHomeActivityLocked(mCurrentUserId, "systemReady");//启动launcher            ...}复制代码

接着进入addAppLocked，启动persistent进程 frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

final ProcessRecord addAppLocked(ApplicationInfo info, boolean isolated,            String abiOverride) {                startProcessLocked(app, "added application", app.processName, abiOverride,                    null /* entryPoint */, null /* entryPointArgs */);            }复制代码

需要继续调用startProcessLocked，尤其注意if (entryPoint == null) entryPoint = "android.app.ActivityThread";,entryPoint将作为zygote fork phone进程的参数。 frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

private final void startProcessLocked(ProcessRecord app, String hostingType,            String hostingNameStr, String abiOverride, String entryPoint, String[] entryPointArgs) {               ...               // Start the process.  It will either succeed and return a result containing            // the PID of the new process, or else throw a RuntimeException.            boolean isActivityProcess = (entryPoint == null);            if (entryPoint == null) entryPoint = "android.app.ActivityThread";//记住这个类名，zygote会反射调用其main()方法            Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "Start proc: " +                    app.processName);            checkTime(startTime, "startProcess: asking zygote to start proc");               Process.ProcessStartResult startResult = Process.start(entryPoint,                    app.processName, uid, uid, gids, debugFlags, mountExternal,                    app.info.targetSdkVersion, app.info.seinfo, requiredAbi, instructionSet,                    app.info.dataDir, entryPointArgs);               ...            }复制代码

3 fork phone进程

Process.start继续调用startViaZygote，startViaZygote继续调zygoteSendArgsAndGetResult，通过LocalSocket，带上类名等参数，if (entryPoint == null) entryPoint = "android.app.ActivityThread",通知Zygote fork phone进程，Zygote通过native方法 fork phone进程后，会反射进入ActivityThread的main方法，main继续调用Application的onCreate。 frameworks/base/core/java/android/os/Process.java

private static ProcessStartResult zygoteSendArgsAndGetResult(ZygoteState zygoteState, ArrayList args){    int sz = args.size();            for (int i = 0; i < sz; i++) {                String arg = args.get(i);                if (arg.indexOf('\n') >= 0) {                    throw new ZygoteStartFailedEx(                            "embedded newlines not allowed");                }                writer.write(arg);                writer.newLine();            }            writer.flush();}复制代码

4 PhoneApp 入口

PhoneApp继承了Application，进程fork后，ActivityThread会去调用其onCreate方法,之后就可以进入电话、数据连接、短彩信流程了。

总结

在ActivityManagerService启动之后，AMS会遍历所有persistent为true的应用，通过过LocalSocket通知Zygote fork phone进程，接着反射执行ActivityThread的main方法，ActivityThread会去调用PhoneApp的onCreate方法。

Phone Application对象的创建

转载于:https://juejin.im/post/5c75022af265da2dc538c4b2

Android Phone进程启动过程

1 注册ActivityManagerService

2 遍历persistent进程

3 fork phone进程

4 PhoneApp 入口

总结

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