之前Android应用程序进程的启动过程文章内有说过，当一个Android应用程序进程启动后，应用程序进程的入口就是ActivityThread类的main函数，ActivityThread的作用管理应用的主进程的执行，并根据AMS的要求，通过IApplicationThread接口负责调度和执行Activities和Broadcasts和其他操作，接下来这里会从main方法开始分析应用的启动流程;
以下源码基于rk3399_industry Android7.1.2
ActivityThread.main
总的来说这里主要是要向AMS发送一个进程启动完成通知，然后接收到回复在进行之后的步骤。
public final class ActivityThread {
final ApplicationThread mAppThread = new ApplicationThread();
public static void main(String[] args) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");
....
//创建主线程的Looper对象
Looper.prepareMainLooper();
//创建ActivityThread实例，创建会同时在它内部创建一个ApplicationThread对象mAppThread
//mAppThread是一个Binder本地对象
//AMS就是通过该对象来和应用程序进程通信的
ActivityThread thread = new ActivityThread();
//调用attch函数向AMS发送一个启动完成的通知
thread.attach(false);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
//进入消息循环
Looper.loop();
....
}
private void attach(boolean system) {
//此时传入的system为false
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {
//开启虚拟机的jit即时编译功能
ViewRootImpl.addFirstDrawHandler(new Runnable() {
@Override
public void run() {
ensureJitEnabled();
}
});
android.ddm.DdmHandleAppName.setAppName("",
UserHandle.myUserId());
RuntimeInit.setApplicationObject(mAppThread.asBinder());
//获得一个AMS的代理对象ActivityManagerProxy
final IActivityManager mgr = ActivityManagerNative.getDefault();
try {
//向AMS发送一个进程间通信请求
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
....
}
// 观察是否快接近heap的上限值
BinderInternal.addGcWatcher(new Runnable() {
@Override public void run() {
if (!mSomeActivitiesChanged) {
return;
}
Runtime runtime = Runtime.getRuntime();
long dalvikMax = runtime.maxMemory();
long dalvikUsed = runtime.totalMemory() - runtime.freeMemory();
//判断已用内存是否超过最大内存的3/4
if (dalvikUsed > ((3*dalvikMax)/4)) {
if (DEBUG_MEMORY_TRIM) Slog.d(TAG, "Dalvik max=" + (dalvikMax/1024)
+ " total=" + (runtime.totalMemory()/1024)
+ " used=" + (dalvikUsed/1024));
mSomeActivitiesChanged = false;
try {
//当已用内存超过最大内存的3/4,则请求释放内存空间
mgr.releaseSomeActivities(mAppThread);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
}
});
} else {
....
}
//添加dropbox日志到libcore
DropBox.setReporter(new DropBoxReporter());
....
}
}
接下来我们就会进入到AMS的代理对象ActivityManagerProxy的attachApplication函数向AMS发送一个进程间通信请求;
ActivityManagerProxy.attachApplication
frameworks/base/core/java/android/app/ActivityManagerNative.java
public abstract class ActivityManagerNative extends Binder implements IActivityManager{
....
class ActivityManagerProxy implements IActivityManager{
....
public void attachApplication(IApplicationThread app) throws RemoteException{
//将传入的参数写入data
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInterfaceToken(IActivityManager.descriptor);
data.writeStrongBinder(app.asBinder());
//通过Binder代理对象mRemote向AMS发送类型为ATTACH_APPLICATION_TRANSACTION的进程间通信请求
//通知应用程序进程启动完成
mRemote.transact(ATTACH_APPLICATION_TRANSACTION, data, reply, 0);
reply.readException();
data.recycle();
reply.recycle();
}
}
}
ActivityManagerService.attachApplication
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public final class ActivityManagerService extends ActivityManagerNative
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
....
public final void attachApplication(IApplicationThread thread) {
synchronized (this) {
//AMS接收到应用程序进程启动完成
int callingPid = Binder.getCallingPid();
final long origId = Binder.clearCallingIdentity();
//执行启动应用的主Activity的操作
attachApplicationLocked(thread, callingPid);
Binder.restoreCallingIdentity(origId);
}
}
//保存进程pid的的对象，在应用程序进程创建完毕后会以pid为关键字，将对应的ProcessRecord对象存入进去
final SparseArray mPidsSelfLocked = new SparseArray();
private final boolean attachApplicationLocked(IApplicationThread thread,
int pid) {
//参数pid为应用程序进程的pid
ProcessRecord app;
//获得当前时间戳
long startTime = SystemClock.uptimeMillis();
if (pid != MY_PID && pid >= 0) {
synchronized (mPidsSelfLocked) {
//获得对应pid所对应的ProcessRecord对象赋值给app
app = mPidsSelfLocked.get(pid);
}
} else {
app = null;
}
....
final String processName = app.processName;
....
//对app对象进行初始化
//这个调用内会将app.thread = thread，即指向传入的ApplicationThread的代理对象
//这样AMS就可以通过这个thread和新创建的应用程序进程进行通信了
app.makeActive(thread, mProcessStats);
app.curAdj = app.setAdj = app.verifiedAdj = ProcessList.INVALID_ADJ;
app.curSchedGroup = app.setSchedGroup = ProcessList.SCHED_GROUP_DEFAULT;
app.forcingToForeground = null;
updateProcessForegroundLocked(app, false, false);
app.hasShownUi = false;
app.debugging = false;
app.cached = false;
app.killedByAm = false;
app.killed = false;
....
//这个PROC_START_TIMEOUT_MSG是一个判断是否启动超时的消息，在创建应用程序进程之前发送
//这里是删除该消息，因为应用程序已经在规定时间内启动起来了
mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);
boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);
....
try {
....
//完成前面的大量准备工作后，重点是这个方法，通知要启动的Application组件
thread.bindApplication(processName, appInfo, providers, app.instrumentationClass,
profilerInfo, app.instrumentationArguments, app.instrumentationWatcher,
app.instrumentationUiAutomationConnection, testMode,
mBinderTransactionTrackingEnabled, enableTrackAllocation,
isRestrictedBackupMode || !normalMode, app.persistent,
new Configuration(mConfiguration), app.compat,
getCommonServicesLocked(app.isolated),
mCoreSettingsObserver.getCoreSettingsLocked());
....
} catch (Exception e) {
....
}
....
if (normalMode) {
try {
//在Application启动完毕后这里启动对应APP的主Activity
if (mStackSupervisor.attachApplicationLocked(app)) {
didSomething = true;
}
} catch (Exception e) {
Slog.wtf(TAG, "Exception thrown launching activities in " + app, e);
badApp = true;
}
}
//当Activity启动完成后启动所有运行在此进程的service
if (!badApp) {
try {
didSomething |= mServices.attachApplicationLocked(app, processName);
} catch (Exception e) {
....
badApp = true;
}
}
....
}
thread是一个ApplicationThreadProxy的Binder代理对象，所以这里最后会调用到ApplicationThreadProxy.bindApplication函数来向之前的应用程序进程发送一个进程间通信请求。
Application的启动
ApplicationThreadProxy.bindApplication
frameworks/base/core/java/android/app/ApplicationThreadNative.java
public abstract class ApplicationThreadNative extends Binder
implements IApplicationThread {
....
class ApplicationThreadProxy implements IApplicationThread {
....
public final void bindApplication(String packageName, ApplicationInfo info,
List providers, ComponentName testName, ProfilerInfo profilerInfo,
Bundle testArgs, IInstrumentationWatcher testWatcher,
IUiAutomationConnection uiAutomationConnection, int debugMode,
boolean enableBinderTracking, boolean trackAllocation, boolean restrictedBackupMode,
boolean persistent, Configuration config, CompatibilityInfo compatInfo,
Map services, Bundle coreSettings) throws RemoteException {
Parcel data = Parcel.obtain();
data.writeInterfaceToken(IApplicationThread.descriptor);
data.writeString(packageName);
info.writeToParcel(data, 0);
data.writeTypedList(providers);
if (testName == null) {
data.writeInt(0);
} else {
data.writeInt(1);
testName.writeToParcel(data, 0);
}
if (profilerInfo != null) {
data.writeInt(1);
profilerInfo.writeToParcel(data, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);
} else {
data.writeInt(0);
}
data.writeBundle(testArgs);
data.writeStrongInterface(testWatcher);
data.writeStrongInterface(uiAutomationConnection);
data.writeInt(debugMode);
data.writeInt(enableBinderTracking ? 1 : 0);
data.writeInt(trackAllocation ? 1 : 0);
data.writeInt(restrictedBackupMode ? 1 : 0);
data.writeInt(persistent ? 1 : 0);
config.writeToParcel(data, 0);
compatInfo.writeToParcel(data, 0);
data.writeMap(services);
data.writeBundle(coreSettings);
mRemote.transact(BIND_APPLICATION_TRANSACTION, data, null,
IBinder.FLAG_ONEWAY);
data.recycle();
}
}
}
这部分就是将传入的参数写入Parcel对象data，然后通过Binder代理对象mRemote向前面的应用程序进程发送一个类行为BIND_APPLICATION_TRANSACTION的进程间通信请求。之后就又回到ApplicationThread.bindApplication函数。
ApplicationThread.bindApplication
frameworks/base/core/java/android/app/ActivityThread.java
public final class ActivityThread {
....
private class ApplicationThread extends ApplicationThreadNative {
....
public final void bindApplication(String processName, ApplicationInfo appInfo,
List providers, 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) {
if (services != null) {
// 在服务管理器中设置服务缓存
ServiceManager.initServiceCache(services);
}
setCoreSettings(coreSettings);
//将传入的应用参数封装成data
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.enableBinderTracking = enableBinderTracking;
data.trackAllocation = trackAllocation;
data.restrictedBackupMode = isRestrictedBackupMode;
data.persistent = persistent;
data.config = config;
data.compatInfo = compatInfo;
data.initProfilerInfo = profilerInfo;
//发送了一个BIND_APPLICATION消息，之后来看消息处理
sendMessage(H.BIND_APPLICATION, data);
}
....
}
....
public void handleMessage(Message msg) {
switch (msg.what) {
....
case BIND_APPLICATION:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "bindApplication");
AppBindData data = (AppBindData)msg.obj;
//在跳转到handleBindApplication方法
handleBindApplication(data);
break;
....
}
}
//handleBindApplication函数非常的长，这里取重点部分讲解
private void handleBindApplication(AppBindData data) {
....
mBoundApplication = data;
....
/初始化一个ContextImpl对象appContext
final ContextImpl appContext = ContextImpl.createAppContext(this, data.info);
//创建一个Application对象
Application app = data.info.makeApplication(data.restrictedBackupMode, null);
mInitialApplication = app;
try{
//调用callApplicationOnCreate，方法内部其实就是调用app.onCreate方法
//之后就进入了Application的生命周期的onCreate()方法了
//mInstrumentation是一个代理层，最终Apllication的创建，Activity的创建，以及生命周期都会经过这个对象去执行
mInstrumentation.callApplicationOnCreate(app);
....
} catch (Exception e) {
....
}
}
}
这部分callApplicationOnCreate比较简单，所以还是关注下如何创建的Application对象，data是一个类型为AppBindData的对象，其info变量的类行为LoadedApk，LoadedApk对象可以说是APK文件在内存中的表示，所以我们要来简单看下LoadedApk.makeApplication函数；
LoadedApk.makeApplication
frameworks/base/core/java/android/app/LoadedApk.java
public final class LoadedApk {
....
public Application makeApplication(boolean forceDefaultAppClass,
Instrumentation instrumentation) {
if (mApplication != null) {
return mApplication;
}
Application app = null;
//获得Application的类名
String appClass = mApplicationInfo.className;
if (forceDefaultAppClass || (appClass == null)) {
appClass = "android.app.Application";
}
try {
java.lang.ClassLoader cl = getClassLoader();
if (!mPackageName.equals("android")) {
initializeJavaContextClassLoader();
}
//创建上下文ContextImpl
ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);
//又回到了当前应用程秀进程的Instrumentation对象中
app = mActivityThread.mInstrumentation.newApplication(
cl, appClass, appContext);
appContext.setOuterContext(app);
} catch (Exception e) {
....
}
mActivityThread.mAllApplications.add(app);
mApplication = app;
....
return app;
}
}
Instrumentation.newApplication
frameworks/base/core/java/android/app/Instrumentation.java
public class Instrumentation {
....
public Application newApplication(ClassLoader cl, String className, Context context)
throws InstantiationException, IllegalAccessException,
ClassNotFoundException {
return newApplication(cl.loadClass(className), context);
}
static public Application newApplication(Class clazz, Context context)
throws InstantiationException, IllegalAccessException,
ClassNotFoundException {
//通过反射创建一个Application对象
Application app = (Application)clazz.newInstance();
//调用其attach方法，将app与context绑定
app.attach(context);
return app;
}
....
}
Application.attach & ContextWrapper.attachBaseContext
frameworks/base/core/java/android/app/Application.java
frameworks/base/core/java/android/content/ContextWrapper.java
public class Application extends ContextWrapper implements ComponentCallbacks2 {
....
final void attach(Context context) {
attachBaseContext(context);
mLoadedApk = ContextImpl.getImpl(context).mPackageInfo;
}
....
}
public class ContextWrapper extends Context {
....
protected void attachBaseContext(Context base) {
if (mBase != null) {
throw new IllegalStateException("Base context already set");
}
mBase = base;
}
....
}
这样就将Application和之前创建的上下文绑定起来了。
Activity和Service的启动
Application启动完成后，回到AMS的attachApplication函数内，之后会调用mStackSupervisor.attachApplicationLocked(app)和mServices.attachApplicationLocked(app,processName)分别启动Activity和Service;
Activity启动：ActivityStackSupervisor.attachApplicationLocked
frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
public final class ActivityStackSupervisor implements DisplayListener {
....
boolean attachApplicationLocked(ProcessRecord app) throws RemoteException {
//获得进程名赋值给processName
final String processName = app.processName;
boolean didSomething = false;
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
ArrayList stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = stacks.get(stackNdx);
if (!isFocusedStack(stack)) {
continue;
}
//获得位于Activity栈顶端的ActivityRecord对象hr，与它对应的Activity组件就是要启动的Activity组件
ActivityRecord hr = stack.topRunningActivityLocked();
if (hr != null) {
//判断要启动的Activity的用户I(UID)和进程名是否与传入的ProcessRecord对象app的一致
if (hr.app == null && app.uid == hr.info.applicationInfo.uid
&& processName.equals(hr.processName)) {
try {
//一致，代表Activity是在app中启动的，调用realStartActivityLocked启动Activity
if (realStartActivityLocked(hr, app, true, true)) {
didSomething = true;
}
} catch (RemoteException e) {
Slog.w(TAG, "Exception in new application when starting activity "
+ hr.intent.getComponent().flattenToShortString(), e);
throw e;
}
}
}
}
}
if (!didSomething) {
ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);
}
return didSomething;
}
....
final boolean realStartActivityLocked(ActivityRecord r, ProcessRecord app,
boolean andResume, boolean checkConfig) throws RemoteException {
....
//将传入的将要启动的Activity的ActivityRecord对象r的app设置为我们应用程序进程的app对象
r.app = app;
....
//idx<0代表r不在app的Activity组建列表中
int idx = app.activities.indexOf(r);
if (idx < 0) {
//将Activity添加进app的Activity组建列表activities中
app.activities.add(r);
}
....
try {
....
//一些准备工作
List results = null;
List newIntents = null;
if (andResume) {
results = r.results;
newIntents = r.newIntents;
}
....
if (r.isHomeActivity()) {
// Home进程是任务的根进程.
mService.mHomeProcess = task.mActivities.get(0).app;
}
....
//通知前面创建的应用程序进程启动Activity组件(即r所描述的Activity)
app.thread.scheduleLaunchActivity(new Intent(r.intent), r.appToken,
System.identityHashCode(r), r.info, new Configuration(mService.mConfiguration),
new Configuration(task.mOverrideConfig), r.compat, r.launchedFromPackage,
task.voiceInteractor, app.repProcState, r.icicle, r.persistentState, results,
newIntents, !andResume, mService.isNextTransitionForward(), profilerInfo,r.task.taskId);
....
} catch (RemoteException e) {
....
}
....
return true;
}
}
在做了一些赋值和一些准备工作之后，就会开始通知前面创建的应用程序进程启动要创建的Activity，由源码可知app是ProcessRecord对象，而app.thread对应位ApplicationThreadProxy代理类，之后看对应的代码；
ApplicationThreadProxy.scheduleLaunchActivity
frameworks/base/core/java/android/app/ApplicationThreadNative.java
public abstract class ApplicationThreadNative extends Binder
implements IApplicationThread {
....
class ApplicationThreadProxy implements IApplicationThread {
....
public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
ActivityInfo info, Configuration curConfig, Configuration overrideConfig,
CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,
int procState, Bundle state, PersistableBundle persistentState,
List pendingResults, List pendingNewIntents,
boolean notResumed, boolean isForward, ProfilerInfo profilerInfo,int taskId) throws RemoteException {
Parcel data = Parcel.obtain();
data.writeInterfaceToken(IApplicationThread.descriptor);
intent.writeToParcel(data, 0);
data.writeStrongBinder(token);
data.writeInt(ident);
info.writeToParcel(data, 0);
curConfig.writeToParcel(data, 0);
if (overrideConfig != null) {
data.writeInt(1);
overrideConfig.writeToParcel(data, 0);
} else {
data.writeInt(0);
}
compatInfo.writeToParcel(data, 0);
data.writeString(referrer);
data.writeStrongBinder(voiceInteractor != null ? voiceInteractor.asBinder() : null);
data.writeInt(procState);
data.writeBundle(state);
data.writePersistableBundle(persistentState);
data.writeTypedList(pendingResults);
data.writeTypedList(pendingNewIntents);
data.writeInt(notResumed ? 1 : 0);
data.writeInt(isForward ? 1 : 0);
if (profilerInfo != null) {
data.writeInt(1);
profilerInfo.writeToParcel(data, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);
} else {
data.writeInt(0);
}
data.writeInt(taskId);
//调用Binder代理对象mRemote发送一个SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION的进程间通信请求
mRemote.transact(SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION, data, null,
IBinder.FLAG_ONEWAY);
data.recycle();
}
....
}
....
}
ApplicationThread.scheduleLaunchActivity
frameworks/base/core/java/android/app/ActivityThread.java
public final class ActivityThread {
....
private class ApplicationThread extends ApplicationThreadNative {
....
public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
ActivityInfo info, Configuration curConfig, Configuration overrideConfig,
CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,
int procState, Bundle state, PersistableBundle persistentState,
List pendingResults, List pendingNewIntents,
boolean notResumed, boolean isForward, ProfilerInfo profilerInfo,int taskId_param) {
updateProcessState(procState, false);
//将要启动的Activity封装成ActivityClientRecord对象r
ActivityClientRecord r = new ActivityClientRecord();
r.token = token;
r.ident = ident;
r.intent = intent;
r.referrer = referrer;
r.voiceInteractor = voiceInteractor;
r.activityInfo = info;
r.compatInfo = compatInfo;
r.state = state;
r.persistentState = persistentState;
r.pendingResults = pendingResults;
r.pendingIntents = pendingNewIntents;
r.startsNotResumed = notResumed;
r.isForward = isForward;
r.profilerInfo = profilerInfo;
r.overrideConfig = overrideConfig;
r.taskId = taskId_param;
updatePendingConfiguration(curConfig);
//发送类型为LAUNCH_ACTIVITY，带着r的消息给创建的应用程序金层呢的消息队列处理
sendMessage(H.LAUNCH_ACTIVITY, r);
}
....
}
....
public void handleMessage(Message msg) {
switch (msg.what) {
....
case LAUNCH_ACTIVITY: {
//将发送来的obj转成ActivityClientRecord对象r
final ActivityClientRecord r = (ActivityClientRecord) msg.obj;
//调用getPackageInfoNoCheck获得一个LoadedApk对象保存在r.的成员函数packageInfo中
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo, r.compatInfo);
//进入函数handleLaunchActivity来启动Activity组件
handleLaunchActivity(r, null, "LAUNCH_ACTIVITY");
} break;
....
}
}
....
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {
....
// 确保我们使用最新的配置运行。
handleConfigurationChanged(null, null);
// 创建Activity前进行初始化
WindowManagerGlobal.initialize();
// performLaunchActivity函数会将Activity启动起来
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
reportSizeConfigurations(r);
Bundle oldState = r.state;
//将Activity组件的状态设置为Resumed，代表它是系统当前显示的Activity
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);
if (!r.activity.mFinished && r.startsNotResumed) {
//如果actvity没有finish，同时并不在resume状态，让Activity进入Pause状态，调用onPause生命方法。下方进入这个方法
performPauseActivityIfNeeded(r, reason);
....
}
} else {
....
}
}
....
//将Activity启动起来
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
....
//获得要启动的Activity组件的包名和类名赋值给component
ComponentName component = r.intent.getComponent();
....
Activity activity = null;
try {
//通过类加载器将component加载到内存中
java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
//构造出一个对应Activity的实例activity
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
....
} catch (Exception e) {
....
}
try {
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if (activity != null) {
//创建一个ContextImpl对象，是创建的Activity的上下文环境
Context appContext = createBaseContextForActivity(r, activity);
....
//传入参数，调用attach进行Activity的初始化
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window);
....
//通知Activity启动起来，callActivityOnCreate内部会调用Activity的生命周期onCreate()
mInstrumentation.callActivityOnCreate(activity, r.state);
//设置一些r的变量
....
}
}
....
//将r的token对象保存在ActivityThread的成员变量mActivities中
mActivities.put(r.token, r);
//r.token是一个Binder代理对象，只想了AMS内部的一个ActivityRecord对象
//这个ActivityRecord和对象r一样，都是用来描述启动的Activity的，只不过前者用于AMS，后者用于应用程序进程中。
} catch (SuperNotCalledException e) {
....
} catch (Exception e) {
....
}
return activity;
}
....
//将Activity组件的状态设置为Resumed，代表它是系统当前显示的Activity
final void handleResumeActivity(IBinder token,
boolean clearHide, boolean isForward, boolean reallyResume, int seq, String reason) {
//获得启动的Activity的ActivityClientRecord对象，并赋值给r
ActivityClientRecord r = mActivities.get(token);
//最后会调用到mInstrumentation.callActivityOnResume，之后Activity的onResume生命周期就会被调用了
r = performResumeActivity(token, clearHide, reason);
if (r != null) {
final Activity a = r.activity;
....
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow();
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
l.softInputMode |= forwardBit;
if (r.mPreserveWindow) {
a.mWindowAdded = true;
r.mPreserveWindow = false;
ViewRootImpl impl = decor.getViewRootImpl();
if (impl != null) {
impl.notifyChildRebuilt();
}
}
if (a.mVisibleFromClient && !a.mWindowAdded) {
a.mWindowAdded = true;
wm.addView(decor, l);
}
} else if (!willBeVisible) {
....
}
....
}
// 通知AMS activity已经进入resume状态
if (reallyResume) {
try {
ActivityManagerNative.getDefault().activityResumed(token);
} catch (RemoteException ex) {
....
}
}
} else {
....
}
}
....
private void performPauseActivityIfNeeded(ActivityClientRecord r, String reason) {
if (r.paused) {
// 已经处于pause状态
return;
}
try {
r.activity.mCalled = false;
//调用Activity的onPause方法，函数内是调用Activity.performPause方法，最后会调用onPause生命周期
mInstrumentation.callActivityOnPause(r.activity);
r.activity.getComponentName().getClassName(), reason);
....
} catch (SuperNotCalledException e) {
....
} catch (Exception e) {
....
}
r.paused = true;
}
....
}
代码中为何需要获得一个LoadedApk对象，原因在于每一个Android应用程序都是打包在一个apk文件中，apk文件中包含了一个Android应用程序的所有资源，所以才需要在启动Activity时加载，为了可以访问到内部的资源文件。在ActivityThread类中就通过LoadedApk独享来描述加载的apk文件。
当我们加载完apk之后，便会进行初始化配置，创建要启动的Activity的实例，以此调用其attach，onCreate，onReume方法和生命周期，中间夹杂着一些上下文创建，参数配置等操作没有细说。
Service启动：ActiveServices.attachApplicationLocked
frameworks/base/services/core/java/com/android/server/am/ActiveServices.java
public final class ActiveServices {
....
boolean attachApplicationLocked(ProcessRecord proc, String processName)
throws RemoteException {
boolean didSomething = false;
// 收集等待在此进程启动的所有服务。
if (mPendingServices.size() > 0) {
ServiceRecord sr = null;
try {
for (int i=0; iApplicationThreadProxy.scheduleCreateService
frameworks/base/core/java/android/app/ApplicationThreadNative.java
public abstract class ApplicationThreadNative extends Binder
implements IApplicationThread {
....
class ApplicationThreadProxy implements IApplicationThread {
....
public final void scheduleCreateService(IBinder token, ServiceInfo info,
CompatibilityInfo compatInfo, int processState) throws RemoteException {
Parcel data = Parcel.obtain();
data.writeInterfaceToken(IApplicationThread.descriptor);
data.writeStrongBinder(token);
info.writeToParcel(data, 0);
compatInfo.writeToParcel(data, 0);
data.writeInt(processState);
try {
//发送一个类型为SCHEDULE_CREATE_SERVICE_TRANSACTION的进程间通信请求
mRemote.transact(SCHEDULE_CREATE_SERVICE_TRANSACTION, data, null,
IBinder.FLAG_ONEWAY);
} catch (TransactionTooLargeException e) {
....
}
data.recycle();
}
....
}
....
}
ApplicationThread.scheduleCreateService
frameworks/base/core/java/android/app/ActivityThread.java
public final class ActivityThread {
....
public final void scheduleCreateService(IBinder token,
ServiceInfo info, CompatibilityInfo compatInfo, int processState) {
updateProcessState(processState, false);
//将要启动的Service的信息封装成一个CreateServiceData对象s
CreateServiceData s = new CreateServiceData();
s.token = token;
s.info = info;
s.compatInfo = compatInfo;
//发送了一个CREATE_SERVICE消息，之后来看消息处理
sendMessage(H.CREATE_SERVICE, s);
}
....
....
public void handleMessage(Message msg) {
switch (msg.what) {
....
case CREATE_SERVICE:
handleCreateService((CreateServiceData)msg.obj);
break;
....
}
}
....
private void handleCreateService(CreateServiceData data) {
....
//获得将要启动的Service组件所在应用程序的LoadedApk对象
LoadedApk packageInfo = getPackageInfoNoCheck(
data.info.applicationInfo, data.compatInfo);
Service service = null;
try {
//获得一个类加载器
java.lang.ClassLoader cl = packageInfo.getClassLoader();
//将要启动的Service加载到内存中，并创建其对应的一个实例service
service = (Service) cl.loadClass(data.info.name).newInstance();
} catch (Exception e) {
....
}
try {
....
//创建Service的一个上下文环境对象实例
ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
context.setOuterContext(service);
//创建/获得一个应用程序对象app
Application app = packageInfo.makeApplication(false, mInstrumentation);
//通过上面传入和创建的参数初始化service
service.attach(context, this, data.info.name, data.token, app,
ActivityManagerNative.getDefault());
//初始化完成后调用Service的生命周期onCreate
service.onCreate();
//以CreateServiceData的token关键字，将service保存在ActivityThread类的成员变量mServices中
//与之前启动Activity类似，这里的token也是一个Binder代理对象
//指向了AMS内部的一个ServiceRecord对象，用来描述启动的Service
mServices.put(data.token, service);
....
} catch (Exception e) {
....
}
}
....
}
至此要启动的Service的onCreate就被调用了，启动完成
这里简单写了一个流程图如下：
activitythread_analysis.png