1, 进程运行

zygoteState创建好进程并且完成初始化操作之后,会调用进程的ActivityThread的main方法, main方法是一个进程最开始执行的地方。

public static void main(String[] args) { Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain"); SamplingProfilerIntegration.start(); CloseGuard.setEnabled(false); Environment.initForCurrentUser(); // Set the reporter for event logging in libcore EventLogger.setReporter(new EventLoggingReporter()); AndroidKeyStoreProvider.install(); // Make sure TrustedCertificateStore looks in the right place for CA certificates final File configDir = Environment.getUserConfigDirectory(UserHandle.myUserId()); TrustedCertificateStore.setDefaultUserDirectory(configDir); Process.setArgV0("<pre-initialized>"); Looper.prepareMainLooper(); ActivityThread thread = new ActivityThread(); thread.attach(false); if (sMainThreadHandler == null) { sMainThreadHandler = thread.getHandler(); } if (false) { Looper.myLooper().setMessageLogging(new LogPrinter(Log.DEBUG, "ActivityThread")); } // End of event ActivityThreadMain. Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER); Looper.loop(); throw new RuntimeException("Main thread loop unexpectedly exited"); }

主要完成2见事情,

1,实例化ActivityThread类并且调用其attach方法;

2,开始主线程的消息循环。

private void attach(boolean system) { sCurrentActivityThread = this; ••• final IActivityManager mgr = ActivityManagerNative.getDefault(); try { mgr.attachApplication(mAppThread); } catch (RemoteException ex) { // Ignore } ••• }

进程刚启动时,什么组件都没有,只能通过Binder机制向AMS所在进程发出请求了

public final void attachApplication(IApplicationThread thread) { synchronized (this) { int callingPid = Binder.getCallingPid(); final long origId = Binder.clearCallingIdentity(); attachApplicationLocked(thread, callingPid); Binder.restoreCallingIdentity(origId); } }

private final boolean attachApplicationLocked(IApplicationThread thread, int pid) { ••• thread.bindApplication(processName, appInfo, providers, app.instrumentationClass, profilerInfo, app.instrumentationArguments, app.instrumentationWatcher, app.instrumentationUiAutomationConnection, testMode, enableOpenGlTrace, isRestrictedBackupMode || !normalMode, app.persistent, new Configuration(mConfiguration), app.compat, getCommonServicesLocked(app.isolated), mCoreSettingsObserver.getCoreSettingsLocked()); updateLruProcessLocked(app, false, null); ••• if (mStackSupervisor.attachApplicationLocked(app)) { didSomething = true; } ••• try { didSomething |= mServices.attachApplicationLocked(app, processName); } ••• try { didSomething |= sendPendingBroadcastsLocked(app); } ••• }

主要做3件事情,

1,启动application和数据库

2,调用updateLruProcessLocked方法调整进程在mLruProcesses列表中的位置

3,分别调用对应方法启动activity,service以及广播三类组件。

在此主要论述第一件事,其他的省略。

public final void bindApplication(String processName, ApplicationInfo appInfo, List<ProviderInfo> providers, ComponentName instrumentationName, ProfilerInfo profilerInfo, Bundle instrumentationArgs, IInstrumentationWatcher instrumentationWatcher, IUiAutomationConnection instrumentationUiConnection, int debugMode, boolean enableOpenGlTrace, boolean isRestrictedBackupMode, boolean persistent, Configuration config, CompatibilityInfo compatInfo, Map<String, IBinder> services, Bundle coreSettings) { ••• AppBindData data = new AppBindData(); data.processName = processName; data.appInfo = appInfo; data.providers = providers; data.instrumentationName = instrumentationName; data.instrumentationArgs = instrumentationArgs; data.instrumentationWatcher = instrumentationWatcher; data.instrumentationUiAutomationConnection = instrumentationUiConnection; data.debugMode = debugMode; data.enableOpenGlTrace = enableOpenGlTrace; data.restrictedBackupMode = isRestrictedBackupMode; data.persistent = persistent; data.config = config; data.compatInfo = compatInfo; data.initProfilerInfo = profilerInfo; sendMessage(H.BIND_APPLICATION, data); }

private void handleBindApplication(AppBindData data) { ••• ContextImpl instrContext = ContextImpl.createAppContext(this, pi); try { java.lang.ClassLoader cl = instrContext.getClassLoader(); mInstrumentation = (Instrumentation) cl.loadClass(data.instrumentationName.getClassName()).newInstance(); } catch (Exception e) { throw new RuntimeException( "Unable to instantiate instrumentation " + data.instrumentationName + ": " + e.toString(), e); } mInstrumentation.init(this, instrContext, appContext, new ComponentName(ii.packageName, ii.name), data.instrumentationWatcher, data.instrumentationUiAutomationConnection); Application app = data.info.makeApplication(data.restrictedBackupMode, null); mInitialApplication = app; if (!data.restrictedBackupMode) { List<ProviderInfo> providers = data.providers; if (providers != null) { installContentProviders(app, providers); // For process that contains content providers, we want to // ensure that the JIT is enabled "at some point". mH.sendEmptyMessageDelayed(H.ENABLE_JIT, 10*1000); } } ••• mInstrumentation.callApplicationOnCreate(app);

1,创建ContextImpl和Instrumentation,Application

2,启动数据库

3,启动Application

1.1 启动数据库

installContentProviders方法和installProvider方法在数据库文章中已经分析过了,在installProvider方法中,在构造contentprovider之后会调用

localProvider.attachInfo(c, info); public void attachInfo(Context context, ProviderInfo info) { attachInfo(context, info, false); } private void attachInfo(Context context, ProviderInfo info, boolean testing) { mNoPerms = testing; if (mContext == null) { mContext = context; if (context != null) { mTransport.mAppOpsManager = (AppOpsManager) context.getSystemService( Context.APP_OPS_SERVICE); } mMyUid = Process.myUid(); if (info != null) { setReadPermission(info.readPermission); setWritePermission(info.writePermission); setPathPermissions(info.pathPermissions); mExported = info.exported; mSingleUser = (info.flags & ProviderInfo.FLAG_SINGLE_USER) != 0; setAuthorities(info.authority); } ContentProvider.this.onCreate(); } }

看到了吧,最后终于会调用ContentProvider的onCreate方法了,其实是调用各自类的onCreate方法,至此,数据库已经启动了。

2.2启动Application

在handleBindApplication方法中,会调用Instrumentation的callApplicationOnCreate方法

mInstrumentation.callApplicationOnCreate(app); public void callApplicationOnCreate(Application app) { app.onCreate(); }

干脆直接的调用Application的onCreate方法。

进程是四大组件的载体,在进程启动四大组件时,首先启动contentprovider。

然后是Application,最后才是activity,service和广播。