framework——应用进程启动流程

1 前言

2 源码分析

2.1 ActivityManagerInternal 初始化流程

（1）请求启动应用进程的入口

/frameworks/base/services/core/java/com/android/server/wm/ActivityStackSupervisor.java

void startSpecificActivityLocked(ActivityRecord r, boolean andResume, boolean checkConfig) {final WindowProcessController wpc = mService.getProcessController(r.processName, r.info.applicationInfo.uid);...    //判断应用进程是否已创建，即 IApplicationThread 是否为空if (wpc != null && wpc.hasThread()) {try {            //启动 ActivityrealStartActivityLocked(r, wpc, andResume, checkConfig);return;}}try {...//应用进程不存在，通知创建应用进程，mService 为 ATMS；mService.mAmInternal 为 ActivityManagerInternal final Message msg = PooledLambda.obtainMessage(ActivityManagerInternal::startProcess, mService.mAmInternal, r.processName,r.info.applicationInfo, knownToBeDead, "activity", r.intent.getComponent());mService.mH.sendMessage(msg);}...}

ActivityStackSupervisor 对象在 ATMS 的 initialize() 方法中创建，并将 ATMS 对象注入到 ActivityStackSupervisor 中。

PooledLambda.obtainMessage() 获取一个 Message，并为其指定 Callback，即执行 mService.mAmInternal 对象的 ActivityManagerInternal::startProcess 函数，函数入参为 r.processName、r.info.applicationInfo 等5个参数。由此可知，ActivityManagerInternal 的 startProcess() 方法是请求启动应用进程的起点。

ActivityManagerInternal 是抽象类，其实现类是 AMS 的内部类 LocalService。接下来将分析 ActivityManagerInternal 的创建流程和 ATMS 获取起对象的流程。

（2）ActivityManagerInternal 的创建

/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

private void start() {...LocalServices.addService(ActivityManagerInternal.class, new LocalService());    //调用 ATMS 的 onActivityManagerInternalAdded 方法进一步初始化mActivityTaskManager.onActivityManagerInternalAdded();...}

start() 方法被 AMS.Lifecycle 的 onStart() 方法调用，onStart() 方法又被 SystemServiceManager 的 startService() 方法调用。

（3）ATMS 获取 ActivityManagerInternal

/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java

public void onActivityManagerInternalAdded() {synchronized (mGlobalLock) {mAmInternal = LocalServices.getService(ActivityManagerInternal.class);...}}

（4）LocalServices

public final class LocalServices {    ...    private static final ArrayMap, Object> sLocalServiceObjects = new ArrayMap, Object>();    public static  T getService(Class type) {        synchronized (sLocalServiceObjects) {            return (T) sLocalServiceObjects.get(type);        }    }    public static  void addService(Class type, T service) {        synchronized (sLocalServiceObjects) {            ...            sLocalServiceObjects.put(type, service);        }    }...}

2.2 AMS 到 ZygoteState

（1）startProcess

/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.LocalService.java

public void startProcess(String processName, ApplicationInfo info, boolean knownToBeDead, String hostingType, ComponentName hostingName) {try {...synchronized (ActivityManagerService.this) {startProcessLocked(processName, info, knownToBeDead, 0 , new HostingRecord(hostingType, hostingName), false, false, true);}}...}

（2）startProcessLocked

/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java

final ProcessRecord startProcessLocked(String processName, ApplicationInfo info, boolean knownToBeDead, int intentFlags, HostingRecord hostingRecord, boolean allowWhileBooting, boolean isolated, boolean keepIfLarge) {    //mProcessList 在定义时就被初始化，即：final ProcessList mProcessList = new ProcessList()return mProcessList.startProcessLocked(processName, info, knownToBeDead, intentFlags, hostingRecord, allowWhileBooting, isolated, 0, keepIfLarge, null, null, null, null);}

（3）startProcessLocked