练车o2o网站设计,徐州小程序开发商,石家庄视频剪辑培训学校,工程建设中常见的法律责任有哪些在学习android框架原理过程中#xff0c;ams的原理非常重要#xff0c;无论是在面试中还是在自己开发类库过程中都会接触到。 1 简述
ActivityManagerService是Android最核心的服务#xff0c;负责管理四大组件的启动、切换、调度等工作。由于AMS的功能和重要性#xff0c… 在学习android框架原理过程中ams的原理非常重要无论是在面试中还是在自己开发类库过程中都会接触到。 1 简述
ActivityManagerService是Android最核心的服务负责管理四大组件的启动、切换、调度等工作。由于AMS的功能和重要性它是运行在SystemServer进程客户端不能直接访问。但是可以通过ActivityManager类的getService方法获取IActivityManager然后与AMS通信。
2 AMS启动流程
init进程
Android系统总共分为4层从上到下为应用层、框架层、系统层、linux内核层。整个系统启动时会先由各个厂商的引导程序拉起加载一些资源然后启动init进程挂载分区创建必要目录初始化日志系统和安全策略。最后解析init.rc文件去启动zygote进程。
zygote进程
通过init进程拉起zygote后
service zygote /system/bin/app_process64 -Xzygote /system/bin --zygote --start-system-server --socket-namezygoteclass mainpriority -20user root # 用户为rootgroup root readproc reserved_disksocket zygote stream 660 root systemsocket usap_pool_primary stream 660 root systemonrestart exec_background - system system -- /system/bin/vdc volume abort_fuseonrestart write /sys/power/state ononrestart restart audioserveronrestart restart cameraserveronrestart restart mediaonrestart restart media.tuneronrestart restart netdonrestart restart wificondtask_profiles ProcessCapacityHigh MaxPerformancecritical window${zygote.critical_window.minute:-off} targetzygote-fatalservice zygote_secondary /system/bin/app_process32 -Xzygote /system/bin --zygote --socket-namezygote_secondary --enable-lazy-preloadclass mainpriority -20user rootgroup root readproc reserved_disksocket zygote_secondary stream 660 root systemsocket usap_pool_secondary stream 660 root systemonrestart restart zygotetask_profiles ProcessCapacityHigh MaxPerformance
会创建JavaVM并注册JNI 通过JNI调用ZygoteInit的main函数进入Zygote的Java框架层创建服务端Socket预加载类和资源并通过runSelectLoop函数等待如ActivityManagerService等的请求。 调用forkSystemServer 来启动SystemServer进程这样系统的关键服务也会由SystemServer进程启动起来。
SystemServer进程
/*** 进程的入口点*/
public static void main(String[] args) {new SystemServer().run();
}private void run() {...// 启动 AMS PowerManagerService PackageManagerService 等服务startBootstrapServices(t);// 启动了BatteryService UsageStatsService WebViewUpdateServicestartCoreServices(t);// CameraService AlarmManagerService VrManagerServicestartOtherServices(t); ...}
Zygote启动后fork的第一个进程为SystemServer这个进程就会去启动一系列的服务AMS服务也是由这个进程启动。
AMS 启动
private void startBootstrapServices(NonNull TimingsTraceAndSlog t) {t.traceBegin(startBootstrapServices);// ...// Activity manager runs the show.// 创建并运行AMSt.traceBegin(StartActivityManager);// TODO: Might need to move after migration to WM.ActivityTaskManagerService atm mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService();mActivityManagerService ActivityManagerService.Lifecycle.startService(mSystemServiceManager, atm);mActivityManagerService.setSystemServiceManager(mSystemServiceManager);mActivityManagerService.setInstaller(installer);mWindowManagerGlobalLock atm.getGlobalLock();t.traceEnd();// ...t.traceEnd(); // startBootstrapServices
}public static final class Lifecycle extends SystemService {private final ActivityManagerService mService;private static ActivityTaskManagerService sAtm;public Lifecycle(Context context) {super(context);mService new ActivityManagerService(context, sAtm);}public static ActivityManagerService startService(SystemServiceManager ssm, ActivityTaskManagerService atm) {sAtm atm;return ssm.startService(ActivityManagerService.Lifecycle.class).getService();}Overridepublic void onStart() {mService.start();}Overridepublic void onBootPhase(int phase) {mService.mBootPhase phase;if (phase PHASE_SYSTEM_SERVICES_READY) {mService.mBatteryStatsService.systemServicesReady();mService.mServices.systemServicesReady();} else if (phase PHASE_ACTIVITY_MANAGER_READY) {mService.startBroadcastObservers();} else if (phase PHASE_THIRD_PARTY_APPS_CAN_START) {mService.mPackageWatchdog.onPackagesReady();}}Overridepublic void onCleanupUser(int userId) {mService.mBatteryStatsService.onCleanupUser(userId);}public ActivityManagerService getService() {return mService;}
}public void startService(NonNull final SystemService service) {// 注册服务mServices.add(service);// 开启服务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);
}private void start() {// ...
}
从代码中可以看出在startBootstrapServices方法中创建了ActivityManagerService服务对象然后在startService方法中调用service.onStart()也就是走Lifecycle中实现的方法然后最终走到start()启动服务。
3 AMS在启动App过程中的体现
fock新进程
我们手机上的App都是在Launcher就是个Actviity中显示的点击图标会触发onClick收到点击事件然后走startActivitySafely方法继续往下走会发现就是startActivity方法往后走的调用。
LauncherAppsService - startActivityAsUser
ActivityTaskManagerService - startActivityAsUser
ActivityStarter - execute
ActivityStarter - startActivityUnchecked
ActivityStarter - startActivityInner
ActivityStack - startActivityLocked
ActivityStack - ensureActivitiesVisible
EnsureActivitiesVisibleHelper - process
EnsureActivitiesVisibleHelper - setActivityVisibilityState
ActivityRecord - makeActiveIfNeeded
ActivityStack - resumeTopActivityUncheckedLocked
ActivityStack - resumeTopActivityInnerLocked
ActivityTaskManagerService - startProcessAsync
ActivityManagerService - startProcess
ActivityManagerService - startProcessLocked
ProcessList - startProcessLocked (指定启动进程后走android.app.ActivityThread main方法 : final String entryPoint android.app.ActivityThread;)
ProcessList - startProcess
ZygoteProcess - start
ZygoteProcess - startViaZygote
zygoteSendArgsAndGetResult
attemptZygoteSendArgsAndGetResultprivate Process.ProcessStartResult attemptZygoteSendArgsAndGetResult(ZygoteState zygoteState, String msgStr) throws ZygoteStartFailedEx {try {final BufferedWriter zygoteWriter zygoteState.mZygoteOutputWriter;final DataInputStream zygoteInputStream zygoteState.mZygoteInputStream;zygoteWriter.write(msgStr);zygoteWriter.flush();// Always read the entire result from the input stream to avoid leaving// bytes in the stream for future process starts to accidentally stumble// upon.Process.ProcessStartResult result new Process.ProcessStartResult();result.pid zygoteInputStream.readInt();result.usingWrapper zygoteInputStream.readBoolean();if (result.pid 0) {throw new ZygoteStartFailedEx(fork() failed);}return result;} catch (IOException ex) {zygoteState.close();Log.e(LOG_TAG, IO Exception while communicating with Zygote - ex.toString());throw new ZygoteStartFailedEx(ex);}
}
Launcher通知AMS启动APP的MainActivity也就是清单文件设置启动的Activity AMS记录要启动的Activity信息并且通知Launcher进入pause状态 Launcher进入pause状态后通知AMS已经paused了可以启动app了 app未开启过所以会通过socket发送消息给AMS AMS在SystemServer进程该进程在启动时执行ZygoteInit.main()后便进入runSelectLoop()循环体内当有客户端连接时便会执行ZygoteConnection.runOnce()方法再经过层层调用后fork出新的应用进程handleChildProc 并且在新进程中创建ActivityThread对象执行其中的main函数方法
ActivityThread
ActivityThread会做很多事我们只分析和app启动与AMS相关的。
public static void main(String[] args) {// ...Looper.prepareMainLooper();ActivityThread thread new ActivityThread();// 绑定Applicationthread.attach(false, startSeq);Looper.loop();// ...
}private void attach(boolean system) { sCurrentActivityThread this;mSystemThread system; // falseif (!system) { // true...// 获取 AMS调用AMS的 attachApplicationfinal IActivityManager mgr ActivityManager.getService();try {mgr.attachApplication(mAppThread);} catch (RemoteException ex) {throw ex.rethrowFromSystemServer();}// Watch for getting close to heap limit....} else { // 系统进程处理逻辑...}...
}
AMS 处理绑定Application
Override
public final void attachApplication(IApplicationThread thread, long startSeq) {if (thread null) {throw new SecurityException(Invalid application interface);}synchronized (this) {int callingPid Binder.getCallingPid();final int callingUid Binder.getCallingUid();final long origId Binder.clearCallingIdentity();attachApplicationLocked(thread, callingPid, callingUid, startSeq);Binder.restoreCallingIdentity(origId);}
}private final boolean attachApplicationLocked(IApplicationThread thread,int pid) {ProcessRecord app;// 根据pid 获取 对应 ProcessRecord// 新进程的名字final String processName app.processName;...thread.bindApplication(processName, appInfo, providerList, null, profilerInfo,null, null, null, testMode,mBinderTransactionTrackingEnabled, enableTrackAllocation,isRestrictedBackupMode || !normalMode, app.isPersistent(),new Configuration(app.getWindowProcessController().getConfiguration()),app.compat, getCommonServicesLocked(app.isolated),mCoreSettingsObserver.getCoreSettingsLocked(),buildSerial, autofillOptions, contentCaptureOptions,app.mDisabledCompatChanges);...//查找所有可运行在该进程中的服务//检查这个进程中是否有下一个广播接收者//检查这个进程中是否有下一个备份代理//上述操作如果出现异常就杀死进程...}
ActivityThread.bindApplication
Override
public final void bindApplication(String processName, ApplicationInfo appInfo,ProviderInfoList providerList, ComponentName instrumentationName,ProfilerInfo profilerInfo, Bundle instrumentationArgs,IInstrumentationWatcher instrumentationWatcher,IUiAutomationConnection instrumentationUiConnection, int debugMode,boolean enableBinderTracking, boolean trackAllocation,boolean isRestrictedBackupMode, boolean persistent, Configuration config,CompatibilityInfo compatInfo, Map services, Bundle coreSettings,String buildSerial, AutofillOptions autofillOptions,ContentCaptureOptions contentCaptureOptions, long[] disabledCompatChanges) {...AppBindData data new AppBindData();data.processName processName;data.appInfo appInfo;...sendMessage(H.BIND_APPLICATION, data);
}private void handleBindApplication(AppBindData data) {...// application oncreatemInstrumentation.callApplicationOnCreate(app);
}
启动MainActivity
App启动时我们通过fork Zygote进程创建了app进程并做了一些application的绑定等等操作。 这些处理好后就可以继续启动MainActivity。
ActivityStack - resumeTopActivityInnerLocked
ActivityStackSupervisor - startSpecificActivity
ActivityStackSupervisor - realStartActivityLockedprivate boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {// ...// Since the start-process is asynchronous, if we already know the process of next// activity isnt running, we can start the process earlier to save the time to wait// for the current activity to be paused.final boolean isTop this taskDisplayArea.getFocusedStack();mAtmService.startProcessAsync(next, false /* knownToBeDead */, isTop,isTop ? pre-top-activity : pre-activity);// ...mStackSupervisor.startSpecificActivity(next, true, true);}boolean realStartActivityLocked(ActivityRecord r, WindowProcessController proc,boolean andResume, boolean checkConfig) throws RemoteException {mService.getLifecycleManager().scheduleTransaction(clientTransaction);
}// 通过aidl进入app所在进程
// 启动MainActivityActivityThread - scheduleTransaction
...
ActivityThread - handleLaunchActivity
ActivityThread - performLaunchActivity
4 重要的类
ActvityRecord
用来存储activity的信息
一个ActivityRecord对应一个Activity一个Activity可能会有多个
ActivityRecord
因为Activity可以被多次启动这个主要取决于其启动模式。
ActivityStack
则是用来管理ActivityRecord的包含了多个ActivityRecord。
ActivityStack
用来存储activity也就是我们常说的activity栈。 ActivityStackSupervisor 用来管理ActivityStack Instrumentation 负责调用Activity和Application生命周期。
5 总结
AMS负责四大组件的启动调度等工作因为在不同进程所以通信会基于binder或者socket。1、AMS是什么时候被初始化的在手机开机SystemServer进程启动后就会启动初始化AMS。2、AMS与Zygote进程是通过什么通信的
