序入口函數(shù)定血，ActivityThread的main()函數(shù)
public static void main(String[] args) {
//此處省略N行.......
//創(chuàng)建Lopper,主線程Looper
Looper.prepareMainLooper();
//創(chuàng)建ActivityThread對(duì)象
ActivityThread thread = new ActivityThread();
//false,首次啟動(dòng)，需要初始化
thread.attach(false);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG, "ActivityThread"));
}
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
// 主線程looper，開啟死循環(huán)蝗罗，不斷處理按鍵义图、觸摸等消息减俏，activity的生命周期也由其處理
//若在activity的某個(gè)生命周期執(zhí)行耗時(shí)操作，那么其他的消息無法及時(shí)執(zhí)行碱工，那么整個(gè)loop循環(huán)會(huì)卡頓
//時(shí)間一長(zhǎng)娃承，就會(huì)觸發(fā)拋出ANR
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
attach()分析
private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
//main入口傳入的fasle
if (!system) {
//先走該分支代碼
//先獲取ActivityManagerService對(duì)象，調(diào)用ActivityManagerService的attachApplication()
final IActivityManager mgr = ActivityManagerNative.getDefault();
try {
// ======= 展開分析1 ========
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
//此處省略N行代碼
} else {
try {
//Instrumentation類會(huì)在應(yīng)用的任何代碼執(zhí)行前被實(shí)列化怕篷，用來監(jiān)控系統(tǒng)與應(yīng)用的交互
//另一個(gè)重要作用是提供Android組件單元測(cè)試历筝。
mInstrumentation = new Instrumentation();
//應(yīng)用進(jìn)程conext創(chuàng)建 ====== 展開分析2 =======
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
、 //創(chuàng)建mInitialApplication ===== 展開分析3 ========
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
DropBox.setReporter(new DropBoxReporter());
ViewRootImpl.addConfigCallback(new ComponentCallbacks2() {
@Override
public void onConfigurationChanged(Configuration newConfig) {
synchronized (mResourcesManager) {
//立即將此更改應(yīng)用于資源廊谓，因?yàn)樵诜祷貢r(shí)梳猪，將查看視圖層次結(jié)構(gòu)。
if (mResourcesManager.applyConfigurationToResourcesLocked(newConfig, null)) {
updateLocaleListFromAppContext(mInitialApplication.getApplicationContext(),
mResourcesManager.getConfiguration().getLocales());
//資源被更改蒸痹，發(fā)送消息通知
if (mPendingConfiguration == null ||
mPendingConfiguration.isOtherSeqNewer(newConfig)) {
mPendingConfiguration = newConfig;
sendMessage(H.CONFIGURATION_CHANGED, newConfig);
}
}
}
}
@Override
public void onLowMemory() {
}
@Override
public void onTrimMemory(int level) {
}
});
====展開分析1 ======
ActivityManagerNative春弥，抽象類，一個(gè)Binder通信類
檢索系統(tǒng)的默認(rèn)/全局活動(dòng)管理器叠荠。
static public IActivityManager getDefault() {
//這里返回的是ActivityManagerService匿沛，繼承自ActivityManagerService
return gDefault.get();
}
最終調(diào)用ActivityManagerService內(nèi)的attachAppliocation()
@Override
public final void attachApplication(IApplicationThread thread) {
synchronized (this) {
int callingPid = Binder.getCallingPid();
final long origId = Binder.clearCallingIdentity();
attachApplicationLocked(thread, callingPid);
Binder.restoreCallingIdentity(origId);
}
}
進(jìn)入attachAoolicationLockede()
boolean attachApplicationLocked(ProcessRecord app) throws RemoteException {
final String processName = app.processName;
boolean didSomething = false;
//遍歷activity棧，找到棧頂?shù)腁ctivity
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
ArrayList<ActivityStack> stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = stacks.get(stackNdx);
if (!isFrontStack(stack)) {
continue;
}
//解鎖
ActivityRecord hr = stack.topRunningActivityLocked(null);
if (hr != null) {
if (hr.app == null && app.uid == hr.info.applicationInfo.uid
&& processName.equals(hr.processName)) {
try {
//找到符合條件的Activity榛鼎，真正啟動(dòng)Activity
if (realStartActivityLocked(hr, app, true, true)) {
didSomething = true;
}
} catch (RemoteException e) {
//此處省略N行......
}
}
}
}
}
//此處省略N行......
return didSomething;
}
realStartActivityLocked()內(nèi)調(diào)用了ActivityThread的scheduleLaunchActivity()
此處給Activity賦值了各種信息逃呼，如token，在Android的Window機(jī)制中借帘，添加Dailog蜘渣、View會(huì)校驗(yàn)token，因此這邊也會(huì)將token信息攜帶下去肺然。
（如："Unable to add window -- token " + attrs.token + " is not valid; is your activity running?這類token異常蔫缸。關(guān)于這塊可以去了解一下窗口機(jī)制）
此段代碼最重要的是最后面的sendMessage。這里發(fā)送了一個(gè)消息际起，交給一個(gè)名為H的handler處理拾碌。H這個(gè)handler幾乎處理所有Activity的生命周期的方法。
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<ResultInfo> pendingResults, List<ReferrerIntent> pendingNewIntents,
boolean notResumed, boolean isForward, ProfilerInfo profilerInfo) {
updateProcessState(procState, false);
ActivityClientRecord r = new ActivityClientRecord();
//賦值各類信息信息
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;
updatePendingConfiguration(curConfig);
//發(fā)送啟動(dòng)Activity的消息街望，使用內(nèi)部繼承Handelr的H校翔，在ActivityThread創(chuàng)建時(shí)初始化
sendMessage(H.LAUNCH_ACTIVITY, r);
}
來看一下H的處理
handleMessage內(nèi)調(diào)用handleLaunchActivity()
case LAUNCH_ACTIVITY: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
final ActivityClientRecord r = (ActivityClientRecord) msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo, r.compatInfo);
handleLaunchActivity(r, null, "LAUNCH_ACTIVITY");
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} bre
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {
unscheduleGcIdler();
//此處省略N行.........
//初始化WindowManagerGlobal
WindowManagerGlobal.initialize();
// ======== performLaunchActivity()內(nèi)部 ============
//1.加載Activity的class類，執(zhí)行其attach()
//2.調(diào)用mInstrumentation.callActivityOnCreate灾前，最終調(diào)用Activity的onCreate()
//3.調(diào)用Activity的start()方法
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
reportSizeConfigurations(r);
Bundle oldState = r.state;
// ========= handleResumeActivity（）內(nèi)部 ==============
//1.獲取window防症，創(chuàng)建DecorView對(duì)象
//2.獲取windowManager，將DecorView添加到wm，此時(shí)開啟view的測(cè)量蔫敲，布局饲嗽，繪制等等
//3.使Activity可見
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);
if (!r.activity.mFinished && r.startsNotResumed) {
performPauseActivityIfNeeded(r, reason);
if (r.isPreHoneycomb()) {
r.state = oldState;
}
}
} else {
try {
ActivityManagerNative.getDefault()
.finishActivity(r.token, Activity.RESULT_CANCELED, null,
Activity.DONT_FINISH_TASK_WITH_ACTIVITY);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
}
====展開分析2 ======
ContextImpl（繼承自Context）的構(gòu)造方法，所以返回的是Context
簡(jiǎn)要看下一源碼奈嘿，針對(duì)Context的分析貌虾，后續(xù)會(huì)展開一篇文章，有興趣的話裙犹，可以關(guān)注我~~
static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo) {
if (packageInfo == null) throw new IllegalArgumentException("packageInfo");
return new ContextImpl(null, mainThread,
packageInfo, null, null, 0, null, null, Display.INVALID_DISPLAY);
}
private ContextImpl(ContextImpl container, ActivityThread mainThread,
LoadedApk packageInfo, IBinder activityToken, UserHandle user, int flags,
Display display, Configuration overrideConfiguration, int createDisplayWithId) {
mOuterContext = this;
//如果創(chuàng)建者沒有指定使用哪個(gè)存儲(chǔ)尽狠，則使用默認(rèn)的應(yīng)用程序位置。
if ((flags & (Context.CONTEXT_CREDENTIAL_PROTECTED_STORAGE
| Context.CONTEXT_DEVICE_PROTECTED_STORAGE)) == 0) {
//此處省略N行代碼
}
//傳入ActvityThread
mMainThread = mainThread;
//傳入activityToken
mActivityToken = activityToken;
mFlags = flags;
if (user == null) {
user = Process.myUserHandle();
}
mUser = user;
mPackageInfo = packageInfo;
//初始化ResourcesManager實(shí)例叶圃，用以獲取資源文件
mResourcesManager = ResourcesManager.getInstance();
///此處省略N行代碼...........
}
======展開分析3 =========
LoadApk類,調(diào)用makeApplication(）入?yún)ⅲ╰rue袄膏，null）。
public Application makeApplication(boolean forceDefaultAppClass,
Instrumentation instrumentation) {
//此處省略N行............
try {
java.lang.ClassLoader cl = getClassLoader();
//此處省略N行............
ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);
//通過mInstrumentation創(chuàng)建Application
//
======= 展開分析4 =========
app = mActivityThread.mInstrumentation.newApplication(
cl, appClass, appContext);
appContext.setOuterContext(app);
} catch (Exception e) {
//此處省略N行............
}
mActivityThread.mAllApplications.add(app);
mApplication = app;
if (instrumentation != null) {
try {
instrumentation.callApplicationOnCreate(app);
} catch (Exception e) {
//此處省略N行............
}
//此處省略N行............
return app;
}
=======展開分析4=======
Instrumetation類掺冠，創(chuàng)建Application哩陕，調(diào)用attach(context)
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 {
Application app = (Application)clazz.newInstance();
app.attach(context);
return app;
}
