大家初學java時候都知道java的程式入口是從main方法進入,那麼Android是基于java編寫的,那Android的程式入口做了哪些操作呢?還有Android的應用程式到底是怎樣啟動的呢?我們一起來看一下.
首先附上ActivityThread.java的main方法:
public static void main(String[] args) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");
SamplingProfilerIntegration.start();
// CloseGuard defaults to true and can be quite spammy. We
// disable it here, but selectively enable it later (via
// StrictMode) on debug builds, but using DropBox, not logs.
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(); //執行個體化Looper并設定到ThreadLocal裡面,指派MainLooper
ActivityThread thread = new ActivityThread(); //執行個體化一個ActivityThread
thread.attach(false); //主要是擷取AMS接口 然後設定ApplicationThread 的接口 給AMS和應用程式通信
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler(); //設定MainHandler 是一些接受生命周期的方法
}
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG, "ActivityThread"));
}
// End of event ActivityThreadMain.
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
Looper.loop(); //開始接收消息
throw new RuntimeException("Main thread loop unexpectedly exited");
}
首先我們看第23行:
Looper.prepareMainLooper();
做Android的都知道Looper是handler機制的一個元件
(那麼這裡就延伸了一個問題,子線程裡面能不能建立Handler呢?答案是可以的,但是必須要建立Looper,那麼就有人問了,為什麼主線程裡面不用建立呢?看了Android的代碼以後知道了,原來Android已經默默的給建立好了,Android的元件的生命周期也都是由Handler來調用的,下面就會看到)
那麼我們來看一下prepareMainLooper()都做了一些什麼事情:
public static void prepareMainLooper() {
prepare(false);
synchronized (Looper.class) {
if (sMainLooper != null) {
throw new IllegalStateException("The main Looper has already been prepared.");
}
sMainLooper = myLooper();
}
}
private static void prepare(boolean quitAllowed) {
if (sThreadLocal.get() != null) {
throw new RuntimeException("Only one Looper may be created per thread");
}
sThreadLocal.set(new Looper(quitAllowed));
}
/**
* Return the Looper object associated with the current thread. Returns
* null if the calling thread is not associated with a Looper.
*/
public static @Nullable Looper myLooper() {
return sThreadLocal.get();
}
private Looper(boolean quitAllowed) {
mQueue = new MessageQueue(quitAllowed);
mThread = Thread.currentThread();
}
好大家看進入了prepareMainLooper以後首先調用了prepare方法,在prepare方法裡面判斷了sThreadLocal!=null以後才往下走,這就解釋了一個線程隻能有一個Looper,執行個體化了一個Looper并設定給sThreadLocal,那麼看到Looper的構造方法裡面建立了MessageQueue一個消息隊列和擷取目前的線程Thread并指派.
然後在prepareMainLooper下面又執行了一句代碼把剛才建立的Looper指派給sMainLooper.
(這個sMainLooper就是主線程的Looper也就是UI線程的Looper,在開發Android應用時有時也會擷取它和目前線程的Looper比較,可以知道目前是不是在主線程....額...有點跑題了)
那麼這段代碼就結束了,我們繼續往下看.
第25行執行個體化了ActivityThread對象:
第26行調用了AcitivityThread對象的attach方法,那麼來看一下究竟做了什麼:
private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {
ViewRootImpl.addFirstDrawHandler(new Runnable() {
@Override
public void run() {
ensureJitEnabled();
}
});
android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",
UserHandle.myUserId());
RuntimeInit.setApplicationObject(mAppThread.asBinder());
final IActivityManager mgr = ActivityManagerNative.getDefault();
try {
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
// Ignore
}
// Watch for getting close to heap limit.
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();
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 {
mgr.releaseSomeActivities(mAppThread);
} catch (RemoteException e) {
}
}
}
});
} else {
// Don't set application object here -- if the system crashes,
// we can't display an alert, we just want to die die die.
android.ddm.DdmHandleAppName.setAppName("system_process",
UserHandle.myUserId());
try {
mInstrumentation = new Instrumentation();
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
// add dropbox logging to libcore
DropBox.setReporter(new DropBoxReporter());
ViewRootImpl.addConfigCallback(new ComponentCallbacks2() {
@Override
public void onConfigurationChanged(Configuration newConfig) {
synchronized (mResourcesManager) {
// We need to apply this change to the resources
// immediately, because upon returning the view
// hierarchy will be informed about it.
if (mResourcesManager.applyConfigurationToResourcesLocked(newConfig, null)) {
// This actually changed the resources! Tell
// everyone about it.
if (mPendingConfiguration == null ||
mPendingConfiguration.isOtherSeqNewer(newConfig)) {
mPendingConfiguration = newConfig;
sendMessage(H.CONFIGURATION_CHANGED, newConfig);
}
}
}
}
@Override
public void onLowMemory() {
}
@Override
public void onTrimMemory(int level) {
}
});
}
調用的時候參數傳遞false說明不是系統調用的,那麼我們就看if語句塊裡面的,主要就看14行和16行的代碼:
final IActivityManager mgr = ActivityManagerNative.getDefault();
mgr.attachApplication(mAppThread);
那麼這兩句代碼首先Android系統中存在一個ActivityManagerService(簡稱AMS)(大白話就叫Activity管理服務),他是來排程Android程式裡面的Activity的開啟等工作.
那麼ActivityManagerNative.getDefault()就是擷取了這個ActivityManagerService的Binder接口(Binder:跨程序通信),然後調用了attachApplication傳入了一個mAppThread.
那麼這個mAppThread是什麼呢?
它是ApplicationThread在全局聲明并初始化,這個東西也是一個繼承了Binder的類,把他傳遞給AMS,以後AMS就拿這個東西和應用程式進行通信.
然後再回到ActivityThread的代碼中,設定了一個sMainThreadHandler,這個thread.getHandler()方法傳回了一個名為H的繼承自Handler的一個類:
private class H extends Handler {
public static final int LAUNCH_ACTIVITY = 100;
public static final int PAUSE_ACTIVITY = 101;
public static final int PAUSE_ACTIVITY_FINISHING= 102;
public static final int STOP_ACTIVITY_SHOW = 103;
public static final int STOP_ACTIVITY_HIDE = 104;
public static final int SHOW_WINDOW = 105;
public static final int HIDE_WINDOW = 106;
public static final int RESUME_ACTIVITY = 107;
public static final int SEND_RESULT = 108;
public static final int DESTROY_ACTIVITY = 109;
public static final int BIND_APPLICATION = 110;
public static final int EXIT_APPLICATION = 111;
public static final int NEW_INTENT = 112;
public static final int RECEIVER = 113;
public static final int CREATE_SERVICE = 114;
public static final int SERVICE_ARGS = 115;
public static final int STOP_SERVICE = 116;
public static final int CONFIGURATION_CHANGED = 118;
public static final int CLEAN_UP_CONTEXT = 119;
public static final int GC_WHEN_IDLE = 120;
public static final int BIND_SERVICE = 121;
public static final int UNBIND_SERVICE = 122;
public static final int DUMP_SERVICE = 123;
public static final int LOW_MEMORY = 124;
public static final int ACTIVITY_CONFIGURATION_CHANGED = 125;
public static final int RELAUNCH_ACTIVITY = 126;
public static final int PROFILER_CONTROL = 127;
public static final int CREATE_BACKUP_AGENT = 128;
public static final int DESTROY_BACKUP_AGENT = 129;
public static final int SUICIDE = 130;
public static final int REMOVE_PROVIDER = 131;
public static final int ENABLE_JIT = 132;
public static final int DISPATCH_PACKAGE_BROADCAST = 133;
public static final int SCHEDULE_CRASH = 134;
public static final int DUMP_HEAP = 135;
public static final int DUMP_ACTIVITY = 136;
public static final int SLEEPING = 137;
public static final int SET_CORE_SETTINGS = 138;
public static final int UPDATE_PACKAGE_COMPATIBILITY_INFO = 139;
public static final int TRIM_MEMORY = 140;
public static final int DUMP_PROVIDER = 141;
public static final int UNSTABLE_PROVIDER_DIED = 142;
public static final int REQUEST_ASSIST_CONTEXT_EXTRAS = 143;
public static final int TRANSLUCENT_CONVERSION_COMPLETE = 144;
public static final int INSTALL_PROVIDER = 145;
public static final int ON_NEW_ACTIVITY_OPTIONS = 146;
public static final int CANCEL_VISIBLE_BEHIND = 147;
public static final int BACKGROUND_VISIBLE_BEHIND_CHANGED = 148;
public static final int ENTER_ANIMATION_COMPLETE = 149;
String codeToString(int code) {
if (DEBUG_MESSAGES) {
switch (code) {
case LAUNCH_ACTIVITY: return "LAUNCH_ACTIVITY";
case PAUSE_ACTIVITY: return "PAUSE_ACTIVITY";
case PAUSE_ACTIVITY_FINISHING: return "PAUSE_ACTIVITY_FINISHING";
case STOP_ACTIVITY_SHOW: return "STOP_ACTIVITY_SHOW";
case STOP_ACTIVITY_HIDE: return "STOP_ACTIVITY_HIDE";
case SHOW_WINDOW: return "SHOW_WINDOW";
case HIDE_WINDOW: return "HIDE_WINDOW";
case RESUME_ACTIVITY: return "RESUME_ACTIVITY";
case SEND_RESULT: return "SEND_RESULT";
case DESTROY_ACTIVITY: return "DESTROY_ACTIVITY";
case BIND_APPLICATION: return "BIND_APPLICATION";
case EXIT_APPLICATION: return "EXIT_APPLICATION";
case NEW_INTENT: return "NEW_INTENT";
case RECEIVER: return "RECEIVER";
case CREATE_SERVICE: return "CREATE_SERVICE";
case SERVICE_ARGS: return "SERVICE_ARGS";
case STOP_SERVICE: return "STOP_SERVICE";
case CONFIGURATION_CHANGED: return "CONFIGURATION_CHANGED";
case CLEAN_UP_CONTEXT: return "CLEAN_UP_CONTEXT";
case GC_WHEN_IDLE: return "GC_WHEN_IDLE";
case BIND_SERVICE: return "BIND_SERVICE";
case UNBIND_SERVICE: return "UNBIND_SERVICE";
case DUMP_SERVICE: return "DUMP_SERVICE";
case LOW_MEMORY: return "LOW_MEMORY";
case ACTIVITY_CONFIGURATION_CHANGED: return "ACTIVITY_CONFIGURATION_CHANGED";
case RELAUNCH_ACTIVITY: return "RELAUNCH_ACTIVITY";
case PROFILER_CONTROL: return "PROFILER_CONTROL";
case CREATE_BACKUP_AGENT: return "CREATE_BACKUP_AGENT";
case DESTROY_BACKUP_AGENT: return "DESTROY_BACKUP_AGENT";
case SUICIDE: return "SUICIDE";
case REMOVE_PROVIDER: return "REMOVE_PROVIDER";
case ENABLE_JIT: return "ENABLE_JIT";
case DISPATCH_PACKAGE_BROADCAST: return "DISPATCH_PACKAGE_BROADCAST";
case SCHEDULE_CRASH: return "SCHEDULE_CRASH";
case DUMP_HEAP: return "DUMP_HEAP";
case DUMP_ACTIVITY: return "DUMP_ACTIVITY";
case SLEEPING: return "SLEEPING";
case SET_CORE_SETTINGS: return "SET_CORE_SETTINGS";
case UPDATE_PACKAGE_COMPATIBILITY_INFO: return "UPDATE_PACKAGE_COMPATIBILITY_INFO";
case TRIM_MEMORY: return "TRIM_MEMORY";
case DUMP_PROVIDER: return "DUMP_PROVIDER";
case UNSTABLE_PROVIDER_DIED: return "UNSTABLE_PROVIDER_DIED";
case REQUEST_ASSIST_CONTEXT_EXTRAS: return "REQUEST_ASSIST_CONTEXT_EXTRAS";
case TRANSLUCENT_CONVERSION_COMPLETE: return "TRANSLUCENT_CONVERSION_COMPLETE";
case INSTALL_PROVIDER: return "INSTALL_PROVIDER";
case ON_NEW_ACTIVITY_OPTIONS: return "ON_NEW_ACTIVITY_OPTIONS";
case CANCEL_VISIBLE_BEHIND: return "CANCEL_VISIBLE_BEHIND";
case BACKGROUND_VISIBLE_BEHIND_CHANGED: return "BACKGROUND_VISIBLE_BEHIND_CHANGED";
case ENTER_ANIMATION_COMPLETE: return "ENTER_ANIMATION_COMPLETE";
}
}
return Integer.toString(code);
}
public void handleMessage(Message msg) {
if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));
switch (msg.what) {
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);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case RELAUNCH_ACTIVITY: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityRestart");
ActivityClientRecord r = (ActivityClientRecord)msg.obj;
handleRelaunchActivity(r);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case PAUSE_ACTIVITY:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");
handlePauseActivity((IBinder)msg.obj, false, (msg.arg1&1) != 0, msg.arg2,
(msg.arg1&2) != 0);
maybeSnapshot();
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case PAUSE_ACTIVITY_FINISHING:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");
handlePauseActivity((IBinder)msg.obj, true, (msg.arg1&1) != 0, msg.arg2,
(msg.arg1&1) != 0);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case STOP_ACTIVITY_SHOW:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");
handleStopActivity((IBinder)msg.obj, true, msg.arg2);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case STOP_ACTIVITY_HIDE:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");
handleStopActivity((IBinder)msg.obj, false, msg.arg2);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case SHOW_WINDOW:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityShowWindow");
handleWindowVisibility((IBinder)msg.obj, true);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case HIDE_WINDOW:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityHideWindow");
handleWindowVisibility((IBinder)msg.obj, false);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case RESUME_ACTIVITY:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityResume");
handleResumeActivity((IBinder) msg.obj, true, msg.arg1 != 0, true);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case SEND_RESULT:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDeliverResult");
handleSendResult((ResultData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case DESTROY_ACTIVITY:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDestroy");
handleDestroyActivity((IBinder)msg.obj, msg.arg1 != 0,
msg.arg2, false);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case BIND_APPLICATION:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "bindApplication");
AppBindData data = (AppBindData)msg.obj;
handleBindApplication(data);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case EXIT_APPLICATION:
if (mInitialApplication != null) {
mInitialApplication.onTerminate();
}
Looper.myLooper().quit();
break;
case NEW_INTENT:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityNewIntent");
handleNewIntent((NewIntentData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case RECEIVER:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "broadcastReceiveComp");
handleReceiver((ReceiverData)msg.obj);
maybeSnapshot();
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case CREATE_SERVICE:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceCreate");
handleCreateService((CreateServiceData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case BIND_SERVICE:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceBind");
handleBindService((BindServiceData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case UNBIND_SERVICE:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceUnbind");
handleUnbindService((BindServiceData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case SERVICE_ARGS:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceStart");
handleServiceArgs((ServiceArgsData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case STOP_SERVICE:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceStop");
handleStopService((IBinder)msg.obj);
maybeSnapshot();
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case CONFIGURATION_CHANGED:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "configChanged");
mCurDefaultDisplayDpi = ((Configuration)msg.obj).densityDpi;
handleConfigurationChanged((Configuration)msg.obj, null);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case CLEAN_UP_CONTEXT:
ContextCleanupInfo cci = (ContextCleanupInfo)msg.obj;
cci.context.performFinalCleanup(cci.who, cci.what);
break;
case GC_WHEN_IDLE:
scheduleGcIdler();
break;
case DUMP_SERVICE:
handleDumpService((DumpComponentInfo)msg.obj);
break;
case LOW_MEMORY:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "lowMemory");
handleLowMemory();
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case ACTIVITY_CONFIGURATION_CHANGED:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityConfigChanged");
handleActivityConfigurationChanged((ActivityConfigChangeData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case PROFILER_CONTROL:
handleProfilerControl(msg.arg1 != 0, (ProfilerInfo)msg.obj, msg.arg2);
break;
case CREATE_BACKUP_AGENT:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "backupCreateAgent");
handleCreateBackupAgent((CreateBackupAgentData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case DESTROY_BACKUP_AGENT:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "backupDestroyAgent");
handleDestroyBackupAgent((CreateBackupAgentData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case SUICIDE:
Process.killProcess(Process.myPid());
break;
case REMOVE_PROVIDER:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "providerRemove");
completeRemoveProvider((ProviderRefCount)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case ENABLE_JIT:
ensureJitEnabled();
break;
case DISPATCH_PACKAGE_BROADCAST:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "broadcastPackage");
handleDispatchPackageBroadcast(msg.arg1, (String[])msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case SCHEDULE_CRASH:
throw new RemoteServiceException((String)msg.obj);
case DUMP_HEAP:
handleDumpHeap(msg.arg1 != 0, (DumpHeapData)msg.obj);
break;
case DUMP_ACTIVITY:
handleDumpActivity((DumpComponentInfo)msg.obj);
break;
case DUMP_PROVIDER:
handleDumpProvider((DumpComponentInfo)msg.obj);
break;
case SLEEPING:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "sleeping");
handleSleeping((IBinder)msg.obj, msg.arg1 != 0);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case SET_CORE_SETTINGS:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "setCoreSettings");
handleSetCoreSettings((Bundle) msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case UPDATE_PACKAGE_COMPATIBILITY_INFO:
handleUpdatePackageCompatibilityInfo((UpdateCompatibilityData)msg.obj);
break;
case TRIM_MEMORY:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "trimMemory");
handleTrimMemory(msg.arg1);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case UNSTABLE_PROVIDER_DIED:
handleUnstableProviderDied((IBinder)msg.obj, false);
break;
case REQUEST_ASSIST_CONTEXT_EXTRAS:
handleRequestAssistContextExtras((RequestAssistContextExtras)msg.obj);
break;
case TRANSLUCENT_CONVERSION_COMPLETE:
handleTranslucentConversionComplete((IBinder)msg.obj, msg.arg1 == 1);
break;
case INSTALL_PROVIDER:
handleInstallProvider((ProviderInfo) msg.obj);
break;
case ON_NEW_ACTIVITY_OPTIONS:
Pair<IBinder, ActivityOptions> pair = (Pair<IBinder, ActivityOptions>) msg.obj;
onNewActivityOptions(pair.first, pair.second);
break;
case CANCEL_VISIBLE_BEHIND:
handleCancelVisibleBehind((IBinder) msg.obj);
break;
case BACKGROUND_VISIBLE_BEHIND_CHANGED:
handleOnBackgroundVisibleBehindChanged((IBinder) msg.obj, msg.arg1 > 0);
break;
case ENTER_ANIMATION_COMPLETE:
handleEnterAnimationComplete((IBinder) msg.obj);
break;
}
if (DEBUG_MESSAGES) Slog.v(TAG, "<<< done: " + codeToString(msg.what));
}
private void maybeSnapshot() {
if (mBoundApplication != null && SamplingProfilerIntegration.isEnabled()) {
// convert the *private* ActivityThread.PackageInfo to *public* known
// android.content.pm.PackageInfo
String packageName = mBoundApplication.info.mPackageName;
android.content.pm.PackageInfo packageInfo = null;
try {
Context context = getSystemContext();
if(context == null) {
Log.e(TAG, "cannot get a valid context");
return;
}
PackageManager pm = context.getPackageManager();
if(pm == null) {
Log.e(TAG, "cannot get a valid PackageManager");
return;
}
packageInfo = pm.getPackageInfo(
packageName, PackageManager.GET_ACTIVITIES);
} catch (NameNotFoundException e) {
Log.e(TAG, "cannot get package info for " + packageName, e);
}
SamplingProfilerIntegration.writeSnapshot(mBoundApplication.processName, packageInfo);
}
}
}
看着是不是很親切,有PAUSE_ACTIVITY、STOP_ACTIVITY、BIND_SERVICE等,就看到了元件的聲明周期都是通過這去發起的.
最後ActivityThread第39行,調用Looper.loop()方法開始循環擷取Message.
完事了? 沒了? 怎麼可能.... 記不記得咱們給AMS設定了一個ApplicationThread,設定了以後AMS就說了,行了可以.
當AMS看我能調用到你了,好,你可以幹你的事了,那麼它會通過ApplicationThread告訴你,那麼來看一下ApplicationThread的類:
private class ApplicationThread extends ApplicationThreadNative {
private static final String DB_INFO_FORMAT = " %8s %8s %14s %14s %s";
private int mLastProcessState = -1;
private void updatePendingConfiguration(Configuration config) {
synchronized (mResourcesManager) {
if (mPendingConfiguration == null ||
mPendingConfiguration.isOtherSeqNewer(config)) {
mPendingConfiguration = config;
}
}
}
public final void schedulePauseActivity(IBinder token, boolean finished,
boolean userLeaving, int configChanges, boolean dontReport) {
sendMessage(
finished ? H.PAUSE_ACTIVITY_FINISHING : H.PAUSE_ACTIVITY,
token,
(userLeaving ? 1 : 0) | (dontReport ? 2 : 0),
configChanges);
}
public final void scheduleStopActivity(IBinder token, boolean showWindow,
int configChanges) {
sendMessage(
showWindow ? H.STOP_ACTIVITY_SHOW : H.STOP_ACTIVITY_HIDE,
token, 0, configChanges);
}
public final void scheduleWindowVisibility(IBinder token, boolean showWindow) {
sendMessage(
showWindow ? H.SHOW_WINDOW : H.HIDE_WINDOW,
token);
}
public final void scheduleSleeping(IBinder token, boolean sleeping) {
sendMessage(H.SLEEPING, token, sleeping ? 1 : 0);
}
public final void scheduleResumeActivity(IBinder token, int processState,
boolean isForward, Bundle resumeArgs) {
updateProcessState(processState, false);
sendMessage(H.RESUME_ACTIVITY, token, isForward ? 1 : 0);
}
public final void scheduleSendResult(IBinder token, List<ResultInfo> results) {
ResultData res = new ResultData();
res.token = token;
res.results = results;
sendMessage(H.SEND_RESULT, res);
}
// we use token to identify this activity without having to send the
// activity itself back to the activity manager. (matters more with ipc)
@Override
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();
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);
sendMessage(H.LAUNCH_ACTIVITY, r);
}
@Override
public final void scheduleRelaunchActivity(IBinder token,
List<ResultInfo> pendingResults, List<ReferrerIntent> pendingNewIntents,
int configChanges, boolean notResumed, Configuration config,
Configuration overrideConfig) {
requestRelaunchActivity(token, pendingResults, pendingNewIntents,
configChanges, notResumed, config, overrideConfig, true);
}
public final void scheduleNewIntent(List<ReferrerIntent> intents, IBinder token) {
NewIntentData data = new NewIntentData();
data.intents = intents;
data.token = token;
sendMessage(H.NEW_INTENT, data);
}
public final void scheduleDestroyActivity(IBinder token, boolean finishing,
int configChanges) {
sendMessage(H.DESTROY_ACTIVITY, token, finishing ? 1 : 0,
configChanges);
}
那麼這裡貼出了ApplicationThread的部分代碼,這個類很多,都是一些建立元件啊,群組件的暫停,銷毀的一些聲明周期,通過Binder機制調用了以後,在方法裡面調用sendMessage()方法,最後會走到剛才H類的handleMessage方法做處理.
那麼主要看一下scheduleLaunchActivity,從AMS傳遞過來一堆參數,都是Activity的一些資訊,把他們都封裝到了ActivityClientRecord對象裡,然後調用sendMessage方法最終調用到handleMessage裡面.
那麼看H類的handleMessage的switch語句,第一個就是LAUNCH_ACTIVITY那麼看一下handleLaunchActivity把ActivityClientRecord傳遞進去,看一下代碼:
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
mSomeActivitiesChanged = true;
if (r.profilerInfo != null) {
mProfiler.setProfiler(r.profilerInfo);
mProfiler.startProfiling();
}
// Make sure we are running with the most recent config.
handleConfigurationChanged(null, null);
if (localLOGV) Slog.v(
TAG, "Handling launch of " + r);
// Initialize before creating the activity
WindowManagerGlobal.initialize(); //建立Activity之前初始化全局視窗管理者
Activity a = performLaunchActivity(r, customIntent); //獲得一個Activity對象
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
Bundle oldState = r.state;
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed);
if (!r.activity.mFinished && r.startsNotResumed) {
// The activity manager actually wants this one to start out
// paused, because it needs to be visible but isn't in the
// foreground. We accomplish this by going through the
// normal startup (because activities expect to go through
// onResume() the first time they run, before their window
// is displayed), and then pausing it. However, in this case
// we do -not- need to do the full pause cycle (of freezing
// and such) because the activity manager assumes it can just
// retain the current state it has.
try {
r.activity.mCalled = false;
mInstrumentation.callActivityOnPause(r.activity);
// We need to keep around the original state, in case
// we need to be created again. But we only do this
// for pre-Honeycomb apps, which always save their state
// when pausing, so we can not have them save their state
// when restarting from a paused state. For HC and later,
// we want to (and can) let the state be saved as the normal
// part of stopping the activity.
if (r.isPreHoneycomb()) {
r.state = oldState;
}
if (!r.activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onPause()");
}
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(r.activity, e)) {
throw new RuntimeException(
"Unable to pause activity "
+ r.intent.getComponent().toShortString()
+ ": " + e.toString(), e);
}
}
r.paused = true;
}
} else {
// If there was an error, for any reason, tell the activity
// manager to stop us.
try {
ActivityManagerNative.getDefault()
.finishActivity(r.token, Activity.RESULT_CANCELED, null, false);
} catch (RemoteException ex) {
// Ignore
}
}
}
那麼主要看一下performLaunchActivity把Activity資訊傳遞進去擷取了一個Activity對象,那麼下面直接就調用resume了,那麼也就是說在performLaunchActivity裡面已經調用了onCreate和onStart了,看一下代碼:
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
// System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");
ActivityInfo aInfo = r.activityInfo; //Activity的資訊,啟動模式Theme 爛七八糟的
if (r.packageInfo == null) {
r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
Context.CONTEXT_INCLUDE_CODE);
}
ComponentName component = r.intent.getComponent(); //應該就是完整的包名+類名
if (component == null) {
component = r.intent.resolveActivity(
mInitialApplication.getPackageManager());
r.intent.setComponent(component);
}
if (r.activityInfo.targetActivity != null) {
component = new ComponentName(r.activityInfo.packageName,
r.activityInfo.targetActivity);
}
Activity activity = null;
try {
java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent); //ClassLoader加載Activity類
StrictMode.incrementExpectedActivityCount(activity.getClass());
r.intent.setExtrasClassLoader(cl);
r.intent.prepareToEnterProcess();
if (r.state != null) {
r.state.setClassLoader(cl);
}
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to instantiate activity " + component
+ ": " + e.toString(), e);
}
}
try {
Application app = r.packageInfo.makeApplication(false, mInstrumentation); //搞到Application
if (localLOGV) Slog.v(TAG, "Performing launch of " + r);
if (localLOGV) Slog.v(
TAG, r + ": app=" + app
+ ", appName=" + app.getPackageName()
+ ", pkg=" + r.packageInfo.getPackageName()
+ ", comp=" + r.intent.getComponent().toShortString()
+ ", dir=" + r.packageInfo.getAppDir());
if (activity != null) {
Context appContext = createBaseContextForActivity(r, activity);
CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager()); //Lable
Configuration config = new Configuration(mCompatConfiguration);
if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "
+ r.activityInfo.name + " with config " + config);
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);
if (customIntent != null) {
activity.mIntent = customIntent;
}
r.lastNonConfigurationInstances = null;
activity.mStartedActivity = false;
int theme = r.activityInfo.getThemeResource();
if (theme != 0) {
activity.setTheme(theme);
}
activity.mCalled = false;
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity, r.state);
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onCreate()");
}
r.activity = activity;
r.stopped = true;
if (!r.activity.mFinished) {
activity.performStart();
r.stopped = false;
}
if (!r.activity.mFinished) {
if (r.isPersistable()) {
if (r.state != null || r.persistentState != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
r.persistentState);
}
} else if (r.state != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
}
}
if (!r.activity.mFinished) {
activity.mCalled = false;
if (r.isPersistable()) {
mInstrumentation.callActivityOnPostCreate(activity, r.state,
r.persistentState);
} else {
mInstrumentation.callActivityOnPostCreate(activity, r.state);
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onPostCreate()");
}
}
}
r.paused = true;
mActivities.put(r.token, r);
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to start activity " + component
+ ": " + e.toString(), e);
}
}
return activity;
}
首先呢通過ActivityClientRecord參數擷取到AcitivtyInfo群組件的包名+類名,然後擷取了ClassLoader類加載器,接下來使用mInstrumentation.newActivity把類加載器,包名及Intent傳遞進去,通過反射來擷取到編寫的Activity類,這樣就擷取到了Activity.
接下來依序擷取了Context,Title之類的配置通過activity調用attach方法設定了以後,擷取了Theme設定給Activity通過mInstrumentation.callActivityOnCreate()間接調用了Activity的方法,然後下面又調用了onStart方法,那麼這個方法結束以後出去下面又調用了onResume(),至此Activity處于Active(活動狀态).
那麼最後說一下Activity的啟動流程.首先呢從Launch(手機桌面),它本身就是一個應用程式.
1.點選一個圖示後他會通過AMS接口告訴AMS我要開啟一個應用程式,
2.然後AMS就通過ApplicationThread告訴Launch進入Pause狀态,
3.然後進入了pause後會告訴AMS我已經pause了,
4.接下來AMS去建立程序啊,什麼Acitivity的任務棧啊供ActivityThread運作
5.,ActivityThread通過AMS的Binder接口傳遞給它ApplicationThread,
6.AMS一看,好沒有問題,你該幹啥幹啥吧,有事喊我.
那麼這就是一個Android應用的啟動流程了,那麼至于Activity的開啟過程呢,就是少了建立程序和Activity任務棧之類的,其他都差不多,都是通過AMS來管理,那麼這篇文章就結束,謝謝.
![Android主線程(ActivityThread)源代碼分析[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)