目錄
4.1 ResumeActivityItem.execute
4.2 ActivityThread.handleResumeActivity
4.2.1 ActivityThread.performResumeActivity
4.2.2 Looper.myQueue().addIdleHandler(new Idler())
4.3 ResumeActivityItem.postExecute
在上篇文章Android | 基於Android9.0的startActivity流程分析（2）：新Activity的onCreate流程的末尾，說到了TransactionExecutor中的executeLifecycleState函數。該函數與onStart流程緊密相關，本篇文章從該函數入手，開始分析onStart流程。
3. 新Activity的onStart流程
先來看看TransactionExecutor.executeLifecycleState函數的源碼重溫一下：
// /frameworks/base/core/java/android/app/servertransaction/TransactionExecutor.java
/** Transition to the final state if requested by the transaction. */
private void executeLifecycleState(ClientTransaction transaction) {
final ActivityLifecycleItem lifecycleItem = transaction.getLifecycleStateRequest();
if (lifecycleItem == null) {
// No lifecycle request, return early.
return;
}
log("Resolving lifecycle state: " + lifecycleItem);
final IBinder token = transaction.getActivityToken();
final ActivityClientRecord r = mTransactionHandler.getActivityClient(token);
if (r == null) {
// Ignore requests for non-existent client records for now.
return;
}
// Cycle to the state right before the final requested state.
cycleToPath(r, lifecycleItem.getTargetState(), true /* excludeLastState */);
// Execute the final transition with proper parameters.
lifecycleItem.execute(mTransactionHandler, token, mPendingActions);
lifecycleItem.postExecute(mTransactionHandler, token, mPendingActions);
}
我們上篇文章說到，此處的lifecycleItem指的其實就是ResumeActivityItem，所以這個函數裏執行的操作是：
- TransactionExecutor.cycleToPath
- ResumeActivityItem.execute：與onResume流程相關
- ResumeActivityItem.postExecute
（1）先來看看TransactionExecutor.cycleToPath函數：
// /frameworks/base/core/java/android/app/servertransaction/TransactionExecutor.java
/**
* Transition the client between states with an option not to perform the last hop in the
* sequence. This is used when resolving lifecycle state request, when the last transition must
* be performed with some specific parameters.
*/
private void cycleToPath(ActivityClientRecord r, int finish,
boolean excludeLastState) {
final int start = r.getLifecycleState();
log("Cycle from: " + start + " to: " + finish + " excludeLastState:" + excludeLastState);
final IntArray path = mHelper.getLifecyclePath(start, finish, excludeLastState);
performLifecycleSequence(r, path);
}
可以看到，這裏調用了performLifecycleSequence函數：
// /frameworks/base/core/java/android/app/servertransaction/TransactionExecutor.java
/** Transition the client through previously initialized state sequence. */
private void performLifecycleSequence(ActivityClientRecord r, IntArray path) {
final int size = path.size(); //此處的size = 1
for (int i = 0, state; i < size; i++) {
state = path.get(i); //state = 2，執行ON_START 的case
log("Transitioning to state: " + state);
switch (state) {
case ON_CREATE:
mTransactionHandler.handleLaunchActivity(r, mPendingActions,
null /* customIntent */);
break;
case ON_START:
mTransactionHandler.handleStartActivity(r, mPendingActions); //調用ActivityThread.handleStartActivity
break;
case ON_RESUME:
mTransactionHandler.handleResumeActivity(r.token, false /* finalStateRequest */,
r.isForward, "LIFECYCLER_RESUME_ACTIVITY");
break;
case ON_PAUSE:
mTransactionHandler.handlePauseActivity(r.token, false /* finished */,
false /* userLeaving */, 0 /* configChanges */, mPendingActions,
"LIFECYCLER_PAUSE_ACTIVITY");
break;
case ON_STOP:
mTransactionHandler.handleStopActivity(r.token, false /* show */,
0 /* configChanges */, mPendingActions, false /* finalStateRequest */,
"LIFECYCLER_STOP_ACTIVITY");
break;
case ON_DESTROY:
mTransactionHandler.handleDestroyActivity(r.token, false /* finishing */,
0 /* configChanges */, false /* getNonConfigInstance */,
"performLifecycleSequence. cycling to:" + path.get(size - 1));
break;
case ON_RESTART:
mTransactionHandler.performRestartActivity(r.token, false /* start */);
break;
default:
throw new IllegalArgumentException("Unexpected lifecycle state: " + state);
}
}
}
接着來看看ActivityThread.handleStartActivity函數：
// /frameworks/base/core/java/android/app/ActivityThread.java
@Override
public void handleStartActivity(ActivityClientRecord r,
PendingTransactionActions pendingActions) {
final Activity activity = r.activity;
if (r.activity == null) {
// TODO(lifecycler): What do we do in this case?
return;
}
if (!r.stopped) {
throw new IllegalStateException("Can't start activity that is not stopped.");
}
if (r.activity.mFinished) {
// TODO(lifecycler): How can this happen?
return;
}
// Start
activity.performStart("handleStartActivity"); //執行Activity的performStart函數
r.setState(ON_START);//將Activity狀態設置爲ON_START
if (pendingActions == null) { //pendingActions不爲空
// No more work to do.
return;
}
// Restore instance state
if (pendingActions.shouldRestoreInstanceState()) { //pendingActions.shouldRestoreInstanceState()值爲true
if (r.isPersistable()) { //r.isPersistable()值爲false
if (r.state != null || r.persistentState != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
r.persistentState);
}
} else if (r.state != null) {//r.state值爲null
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
}
}
// Call postOnCreate()
if (pendingActions.shouldCallOnPostCreate()) { //r.state值爲true
activity.mCalled = false;
if (r.isPersistable()) { //r.isPersistable()值爲false
mInstrumentation.callActivityOnPostCreate(activity, r.state,
r.persistentState);
} else {
mInstrumentation.callActivityOnPostCreate(activity, r.state); //調用Instrumentation.callActivityOnPostCreate
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString()
+ " did not call through to super.onPostCreate()");
}
}
}
主要完成的操作：
- Activity.performStart
- Instrumetation.callActivityOnPostCreate
先看Activity.performStart：
// /frameworks/base/core/java/android/app/Activity.java
final void performStart(String reason) {
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
mFragments.noteStateNotSaved();
mCalled = false;
mFragments.execPendingActions();
mInstrumentation.callActivityOnStart(this); //調用Instrumentation.callActivityOnStart
writeEventLog(LOG_AM_ON_START_CALLED, reason);
if (!mCalled) {
throw new SuperNotCalledException(
"Activity " + mComponent.toShortString() +
" did not call through to super.onStart()");
}
mFragments.dispatchStart(); //Fragment的start操作
mFragments.reportLoaderStart();
boolean isAppDebuggable =
(mApplication.getApplicationInfo().flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0;
// This property is set for all non-user builds except final release
boolean isDlwarningEnabled = SystemProperties.getInt("ro.bionic.ld.warning", 0) == 1;
...
mActivityTransitionState.enterReady(this);
}
調用了Instrumentation.callActivityOnStart函數：
// /frameworks/base/core/java/android/app/Instrumentation.java
/**
* Perform calling of an activity's {@link Activity#onStart}
* method. The default implementation simply calls through to that method.
*
* @param activity The activity being started.
*/
public void callActivityOnStart(Activity activity) {
activity.onStart();
}
至此，Activity的onStart被調用。
再來看看Instrumentation.callActivityOnPostCreate：
// /frameworks/base/core/java/android/app/Instrumentation.java
/**
* Perform calling of an activity's {@link Activity#onPostCreate} method.
* The default implementation simply calls through to that method.
*
* @param activity The activity being created.
* @param icicle The previously frozen state (or null) to pass through to
* onPostCreate().
*/
public void callActivityOnPostCreate(Activity activity, Bundle icicle) {
activity.onPostCreate(icicle);
}
調用了Activity.onPostCreate：
// /frameworks/base/core/java/android/app/Activity.java
/**
* Called when activity start-up is complete (after {@link #onStart}
* and {@link #onRestoreInstanceState} have been called). Applications will
* generally not implement this method; it is intended for system
* classes to do final initialization after application code has run.
*
* <p><em>Derived classes must call through to the super class's
* implementation of this method. If they do not, an exception will be
* thrown.</em></p>
*
* @param savedInstanceState If the activity is being re-initialized after
* previously being shut down then this Bundle contains the data it most
* recently supplied in {@link #onSaveInstanceState}. <b><i>Note: Otherwise it is null.</i></b>
* @see #onCreate
*/
@CallSuper
protected void onPostCreate(@Nullable Bundle savedInstanceState) {
if (!isChild()) {
mTitleReady = true;
onTitleChanged(getTitle(), getTitleColor()); //更新title
}
mCalled = true;
}
protected void onTitleChanged(CharSequence title, int color) {
if (mTitleReady) {
final Window win = getWindow();
if (win != null) {
win.setTitle(title);
if (color != 0) {
win.setTitleColor(color);
}
}
if (mActionBar != null) {
mActionBar.setWindowTitle(title);
}
}
}
同樣的，來個思維導圖回顧一下onStart流程，該圖接着onCreate的流程。
4. 新Activity的onResume流程
緊接上文，上文分析了TransactionExecutor.executeLifecycleState函數裏執行了如下三個操作：
- TransactionExecutor.cycleToPath
- ResumeActivityItem.execute：與onResume流程相關
- ResumeActivityItem.postExecute
其中僅分析了cycleToPath函數，接下來看看ResumeActivityItem.execute函數。
4.1 ResumeActivityItem.execute
// /frameworks/base/core/java/android/app/servertransaction/ResumeActivityItem.java
@Override
public void execute(ClientTransactionHandler client, IBinder token,
PendingTransactionActions pendingActions) {
Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityResume");
client.handleResumeActivity(token, true /* finalStateRequest */, mIsForward,
"RESUME_ACTIVITY");
Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);
}
同樣地調用到了ActivityThread.handleResumeActivity。
4.2 ActivityThread.handleResumeActivity
// /frameworks/base/core/java/android/app/ActivityThread.java
@Override
public void handleResumeActivity(IBinder token, boolean finalStateRequest, boolean isForward,
String reason) {
// If we are getting ready to gc after going to the background, well
// we are back active so skip it.
unscheduleGcIdler();
...
// TODO Push resumeArgs into the activity for consideration
final ActivityClientRecord r = performResumeActivity(token, finalStateRequest, reason);
if (r == null) {
// We didn't actually resume the activity, so skipping any follow-up actions.
return;
}
...
// If the window hasn't yet been added to the window manager,
// and this guy didn't finish itself or start another activity,
// then go ahead and add the window.
boolean willBeVisible = !a.mStartedActivity; //結果爲true
...
// Get rid of anything left hanging around.
cleanUpPendingRemoveWindows(r, false /* force */);
// The window is now visible if it has been added, we are not
// simply finishing, and we are not starting another activity.
//r.activity.mFinished=false; willBeVisible=true; r.activity.mDecor=DecorView@36c7de6[SecondActivity]; r.hideForNow=false
if (!r.activity.mFinished && willBeVisible && r.activity.mDecor != null && !r.hideForNow) {
if (r.newConfig != null) { //r.newConfig 值爲 null
...
}
...
}
...
if (localLOGV) Slog.v(TAG, "Scheduling idle handler for " + r);
Looper.myQueue().addIdleHandler(new Idler()); //消息隊列裏沒有消息時執行Idler中的queueIdler
}
可以看到，主要的操作：
- ActivityThread.performResumeActivity
- ActivityThread.cleanUpPendingRemoveWindos
- Looper.myQueue().addIdleHandler(new Idler())：主線程的消息循環爲空時執行
4.2.1 ActivityThread.performResumeActivity
先來看看performResumeActivity：
// /frameworks/base/core/java/android/app/ActivityThread.java
/**
* Resume the activity.
* @param token Target activity token.
* @param finalStateRequest Flag indicating if this is part of final state resolution for a
* transaction.
* @param reason Reason for performing the action.
*
* @return The {@link ActivityClientRecord} that was resumed, {@code null} otherwise.
*/
@VisibleForTesting
public ActivityClientRecord performResumeActivity(IBinder token, boolean finalStateRequest,
String reason) {
final ActivityClientRecord r = mActivities.get(token);
if (localLOGV) {
Slog.v(TAG, "Performing resume of " + r + " finished=" + r.activity.mFinished);
}
if (r == null || r.activity.mFinished) {
return null;
}
if (r.getLifecycleState() == ON_RESUME) { //此時Activity的狀態爲ON_START,所以不執行
...
return null;
}
if (finalStateRequest) { //該值爲true
r.hideForNow = false;
r.activity.mStartedActivity = false;
}
try {
r.activity.onStateNotSaved();
r.activity.mFragments.noteStateNotSaved();
checkAndBlockForNetworkAccess();
if (r.pendingIntents != null) { //r.pendingIntents值爲null
deliverNewIntents(r, r.pendingIntents);
r.pendingIntents = null;
}
if (r.pendingResults != null) {//r.pendingResults值爲null
deliverResults(r, r.pendingResults, reason);
r.pendingResults = null;
}
r.activity.performResume(r.startsNotResumed, reason); //【調用activity.performResume執行resume流程】
r.state = null;
r.persistentState = null;
r.setState(ON_RESUME); //設置Activity的狀態爲ON_RESUME
} catch (Exception e) {
if (!mInstrumentation.onException(r.activity, e)) {
throw new RuntimeException("Unable to resume activity "
+ r.intent.getComponent().toShortString() + ": " + e.toString(), e);
}
}
return r;
}
可見主要完成的操作是調用Activity.performResume函數：
// /frameworks/base/core/java/android/app/Activity.java
final void performResume(boolean followedByPause, String reason) {
performRestart(true /* start */, reason); //該函數中因爲mStopped = false，所以實際沒有什麼操作
mFragments.execPendingActions(); //Fragment相關的操作
mLastNonConfigurationInstances = null;
if (mAutoFillResetNeeded) { //自動填充
// When Activity is destroyed in paused state, and relaunch activity, there will be
// extra onResume and onPause event, ignore the first onResume and onPause.
// see ActivityThread.handleRelaunchActivity()
mAutoFillIgnoreFirstResumePause = followedByPause;
if (mAutoFillIgnoreFirstResumePause && DEBUG_LIFECYCLE) {
Slog.v(TAG, "autofill will ignore first pause when relaunching " + this);
}
}
mCalled = false;
// mResumed is set by the instrumentation
mInstrumentation.callActivityOnResume(this); //【調用Instrumentation.callActivityOnResume執行onResume流程】
...
mFragments.dispatchResume(); //Fragment相關的操作
mFragments.execPendingActions();//Fragment相關的操作
onPostResume();
...
}
可見，調用了Instrumentation.callActivityOnResume函數：
// /frameworks/base/core/java/android/app/Instrumentation.java
/**
* Perform calling of an activity's {@link Activity#onResume} method. The
* default implementation simply calls through to that method.
*
* @param activity The activity being resumed.
*/
public void callActivityOnResume(Activity activity) {
activity.mResumed = true;
activity.onResume(); //調用Activity的onResume函數
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i<N; i++) {
final ActivityMonitor am = mActivityMonitors.get(i);
am.match(activity, activity, activity.getIntent());
}
}
}
}
至此，Activity的onResume函數被調用了。同樣地，思維導圖回顧流程。
4.2.2 Looper.myQueue().addIdleHandler(new Idler())
在主線程的消息循環中沒有消息時，執行Idler中的函數queueIdle，運行於應用進程的主線程。該函數的調用堆棧：
D ActivityThread: Idler:queueIdle
D ActivityThread: java.lang.Throwable
D ActivityThread: at android.app.ActivityThread$Idler.queueIdle(ActivityThread.java:1866)
D ActivityThread: at android.os.MessageQueue.next(MessageQueue.java:395)
D ActivityThread: at android.os.Looper.loop(Looper.java:160)
D ActivityThread: at android.app.ActivityThread.main(ActivityThread.java:6833)
D ActivityThread: at java.lang.reflect.Method.invoke(Native Method)
D ActivityThread: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
D ActivityThread: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:911)
先看Looper.myQueue()：
// /frameworks/base/core/java/android/os/Looper.java
/**
* Return the {@link MessageQueue} object associated with the current
* thread. This must be called from a thread running a Looper, or a
* NullPointerException will be thrown.
*/
public static @NonNull MessageQueue myQueue() {
return myLooper().mQueue;
}
/**
* 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();
}
即addIdleHandler實質是調用的MessageQueue.addIdleHandler函數：
// /frameworks/base/core/java/android/os/MessageQueue.java
private final ArrayList<IdleHandler> mIdleHandlers = new ArrayList<IdleHandler>();
/**
* Add a new {@link IdleHandler} to this message queue. This may be
* removed automatically for you by returning false from
* {@link IdleHandler#queueIdle IdleHandler.queueIdle()} when it is
* invoked, or explicitly removing it with {@link #removeIdleHandler}.
*
* <p>This method is safe to call from any thread.
*
* @param handler The IdleHandler to be added.
*/
public void addIdleHandler(@NonNull IdleHandler handler) {
if (handler == null) {
throw new NullPointerException("Can't add a null IdleHandler");
}
synchronized (this) {
mIdleHandlers.add(handler); //將new 出來的Idler添加到mIdleHandlers中
}
}
現在再來看看queueIdle函數的源碼：
private class Idler implements MessageQueue.IdleHandler {
@Override
public final boolean queueIdle() {
ActivityClientRecord a = mNewActivities;
boolean stopProfiling = false;
if (mBoundApplication != null && mProfiler.profileFd != null
&& mProfiler.autoStopProfiler) {
stopProfiling = true;
}
if (a != null) {
mNewActivities = null;
IActivityManager am = ActivityManager.getService();
ActivityClientRecord prev;
do {
if (localLOGV) Slog.v(
TAG, "Reporting idle of " + a +
" finished=" +
(a.activity != null && a.activity.mFinished));
if (a.activity != null && !a.activity.mFinished) {
try {
am.activityIdle(a.token, a.createdConfig, stopProfiling); //跨進程調用AMS.activityIdle函數
a.createdConfig = null;
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
prev = a;
a = a.nextIdle;
prev.nextIdle = null;
} while (a != null);
}
if (stopProfiling) {
mProfiler.stopProfiling();
}
ensureJitEnabled();
return false;
}
}
跨進程調用了AMS.activityIdle函數：
// /frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
@Override
public final void activityIdle(IBinder token, Configuration config, boolean stopProfiling) {
final long origId = Binder.clearCallingIdentity();
synchronized (this) {
ActivityStack stack = ActivityRecord.getStackLocked(token);
if (stack != null) {
ActivityRecord r =
mStackSupervisor.activityIdleInternalLocked(token, false /* fromTimeout */,
false /* processPausingActivities */, config);
if (stopProfiling) {
if ((mProfileProc == r.app) && mProfilerInfo != null) {
clearProfilerLocked();
}
}
}
}
Binder.restoreCallingIdentity(origId);
}
調用了ActivityStackSupervisor.activityIdleInternalLocked函數：
// /frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
// Checked.
@GuardedBy("mService")
final ActivityRecord activityIdleInternalLocked(final IBinder token, boolean fromTimeout,
boolean processPausingActivities, Configuration config) {
if (DEBUG_ALL) Slog.v(TAG, "Activity idle: " + token);
ArrayList<ActivityRecord> finishes = null;
ArrayList<UserState> startingUsers = null;
int NS = 0;
int NF = 0;
boolean booting = false;
boolean activityRemoved = false;
ActivityRecord r = ActivityRecord.forTokenLocked(token);
if (r != null) { //r 爲新啓動的Activity
if (DEBUG_IDLE) Slog.d(TAG_IDLE, "activityIdleInternalLocked: Callers="
+ Debug.getCallers(4));
mHandler.removeMessages(IDLE_TIMEOUT_MSG, r); //remove IDLE_TIMEOUT_MSG消息
r.finishLaunchTickingLocked();
if (fromTimeout) { //值爲false
reportActivityLaunchedLocked(fromTimeout, r, -1, -1);
}
// This is a hack to semi-deal with a race condition
// in the client where it can be constructed with a
// newer configuration from when we asked it to launch.
// We'll update with whatever configuration it now says
// it used to launch.
if (config != null) { //config不爲空
r.setLastReportedGlobalConfiguration(config);
}
// We are now idle. If someone is waiting for a thumbnail from
// us, we can now deliver.
r.idle = true;
//Slog.i(TAG, "IDLE: mBooted=" + mBooted + ", fromTimeout=" + fromTimeout);
if (isFocusedStack(r.getStack()) || fromTimeout) {
booting = checkFinishBootingLocked();
}
}
if (allResumedActivitiesIdle()) { //【1】檢測是否所有的resumed activity 都是idle狀態
if (r != null) {
mService.scheduleAppGcsLocked();
}
if (mLaunchingActivity.isHeld()) { //結果爲true，因爲持有了WakeLock
mHandler.removeMessages(LAUNCH_TIMEOUT_MSG); //移除LAUNCH_TIMEOUT_MSG
if (VALIDATE_WAKE_LOCK_CALLER &&
Binder.getCallingUid() != Process.myUid()) {
throw new IllegalStateException("Calling must be system uid");
}
mLaunchingActivity.release();
}
ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);
}
// Atomically retrieve all of the other things to do.
final ArrayList<ActivityRecord> stops = processStoppingActivitiesLocked(r,
true /* remove */, processPausingActivities); //【2】獲取stopping的activity
NS = stops != null ? stops.size() : 0;
if ((NF = mFinishingActivities.size()) > 0) { //mFinishingActivities.size()=0
finishes = new ArrayList<>(mFinishingActivities);
mFinishingActivities.clear();
}
if (mStartingUsers.size() > 0) { //mStartingUsers.size()=0
startingUsers = new ArrayList<>(mStartingUsers);
mStartingUsers.clear();
}
// Stop any activities that are scheduled to do so but have been
// waiting for the next one to start.
for (int i = 0; i < NS; i++) { //【3】NS=0,for循環不會執行
r = stops.get(i);
final ActivityStack stack = r.getStack();
if (stack != null) {
if (r.finishing) {
stack.finishCurrentActivityLocked(r, ActivityStack.FINISH_IMMEDIATELY, false,
"activityIdleInternalLocked");
} else {
stack.stopActivityLocked(r);
}
}
}
// Finish any activities that are scheduled to do so but have been
// waiting for the next one to start.
for (int i = 0; i < NF; i++) { //【4】NF=0,for循環不會執行
r = finishes.get(i);
final ActivityStack stack = r.getStack();
if (stack != null) {
activityRemoved |= stack.destroyActivityLocked(r, true, "finish-idle");
}
}
if (!booting) { // booting=false
// Complete user switch
if (startingUsers != null) { //startingUsers = null
for (int i = 0; i < startingUsers.size(); i++) {
mService.mUserController.finishUserSwitch(startingUsers.get(i));
}
}
}
mService.trimApplications(); //調用AMS.trimApplications
//dump();
//mWindowManager.dump();
if (activityRemoved) { //activityRemoved=false
resumeFocusedStackTopActivityLocked();
}
return r;
}
這個函數裏有兩個主要操作：
- allResumedActivitiesIdle()：是否所有resumed activity都是idle狀態
- processStoppingActivitiesLocked：獲取stopping的activity
// /frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
boolean allResumedActivitiesIdle() {
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
final ActivityDisplay display = mActivityDisplays.valueAt(displayNdx);
for (int stackNdx = display.getChildCount() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = display.getChildAt(stackNdx);
if (!isFocusedStack(stack) || stack.numActivities() == 0) {
continue;
}
final ActivityRecord resumedActivity = stack.getResumedActivity(); //resumedActivity 爲新啓動的Activity
if (resumedActivity == null || !resumedActivity.idle) { //if條件不滿足
if (DEBUG_STATES) Slog.d(TAG_STATES, "allResumedActivitiesIdle: stack="
+ stack.mStackId + " " + resumedActivity + " not idle");
return false;
}
}
}
// Send launch end powerhint when idle
sendPowerHintForLaunchEndIfNeeded();
return true; //返回true
}
// /frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.java
final ArrayList<ActivityRecord> processStoppingActivitiesLocked(ActivityRecord idleActivity,
boolean remove, boolean processPausingActivities) {
ArrayList<ActivityRecord> stops = null;
final boolean nowVisible = allResumedActivitiesVisible();
for (int activityNdx = mStoppingActivities.size() - 1; activityNdx >= 0; --activityNdx) {
ActivityRecord s = mStoppingActivities.get(activityNdx);
boolean waitingVisible = mActivitiesWaitingForVisibleActivity.contains(s);
if (DEBUG_STATES) Slog.v(TAG, "Stopping " + s + ": nowVisible=" + nowVisible
+ " waitingVisible=" + waitingVisible + " finishing=" + s.finishing);
if (waitingVisible && nowVisible) {
mActivitiesWaitingForVisibleActivity.remove(s);
waitingVisible = false;
if (s.finishing) {
// If this activity is finishing, it is sitting on top of
// everyone else but we now know it is no longer needed...
// so get rid of it. Otherwise, we need to go through the
// normal flow and hide it once we determine that it is
// hidden by the activities in front of it.
if (DEBUG_STATES) Slog.v(TAG, "Before stopping, can hide: " + s);
s.setVisibility(false);
}
}
if (remove) {
final ActivityStack stack = s.getStack();
final boolean shouldSleepOrShutDown = stack != null
? stack.shouldSleepOrShutDownActivities()
: mService.isSleepingOrShuttingDownLocked();
if (!waitingVisible || shouldSleepOrShutDown) {
if (!processPausingActivities && s.isState(PAUSING)) {
// Defer processing pausing activities in this iteration and reschedule
// a delayed idle to reprocess it again
removeTimeoutsForActivityLocked(idleActivity);
scheduleIdleTimeoutLocked(idleActivity);
continue;
}
if (DEBUG_STATES) Slog.v(TAG, "Ready to stop: " + s);
if (stops == null) {
stops = new ArrayList<>();
}
stops.add(s);
mStoppingActivities.remove(activityNdx);
}
}
}
return stops;
}
網上大部分的文章，在說到原Activity的onStop流程時，都說是從queueIdle函數中的如下代碼塊：
// Stop any activities that are scheduled to do so but have been
// waiting for the next one to start.
for (int i = 0; i < NS; i++) { //【3】NS=0,for循環不會執行
r = stops.get(i);
final ActivityStack stack = r.getStack();
if (stack != null) {
if (r.finishing) {
stack.finishCurrentActivityLocked(r, ActivityStack.FINISH_IMMEDIATELY, false,
"activityIdleInternalLocked");
} else {
stack.stopActivityLocked(r);
}
}
}
通過此處的ActivityStack.stopActivityLocked函數完成了原Activity的onStop流程。但是通過在源碼中添加log確認，此時NS =0，該for循環並不會執行。所以onStop流程並不是從此處完成的。如果不對之處，歡迎指正。
此處補充一下更完整一些的思維導圖：
4.3 ResumeActivityItem.postExecute
// /frameworks/base/core/java/android/app/servertransaction/ResumeActivityItem.java
@Override
public void postExecute(ClientTransactionHandler client, IBinder token,
PendingTransactionActions pendingActions) {
try {
// TODO(lifecycler): Use interface callback instead of AMS.
ActivityManager.getService().activityResumed(token); //【跨進程調用到AMS.activityResumed】
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
跨進程調用了AMS.activityResumed函數：
// /frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
WindowManagerService mWindowManager;
@Override
public final void activityResumed(IBinder token) {
final long origId = Binder.clearCallingIdentity();
synchronized(this) {
ActivityRecord.activityResumedLocked(token);
mWindowManager.notifyAppResumedFinished(token);
}
Binder.restoreCallingIdentity(origId);
}
該函數完成的操作：
- ActivityRecord.activityResumedLocked
- WMS.notifyAppResumedFinished
先看activityResumedLocked函數：
// /frameworks/base/core/java/android/app/ActivityRecord.java
static void activityResumedLocked(IBinder token) {
final ActivityRecord r = ActivityRecord.forTokenLocked(token);
if (DEBUG_SAVED_STATE) Slog.i(TAG_STATES, "Resumed activity; dropping state of: " + r);
if (r != null) {
r.icicle = null;
r.haveState = false;
}
}
再看看WMS.notifyAppResumedFinished：
// /frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
final UnknownAppVisibilityController mUnknownAppVisibilityController =
new UnknownAppVisibilityController(this);
public void notifyAppResumedFinished(IBinder token) {
synchronized (mWindowMap) {
final AppWindowToken appWindow = mRoot.getAppWindowToken(token);
if (appWindow != null) {
mUnknownAppVisibilityController.notifyAppResumedFinished(appWindow);
}
}
}
// /frameworks/base/services/core/java/com/android/server/wm/UnknownAppVisibilityController.java
// Set of apps for which we don't know yet whether it's visible or not, depending on what kind
// of lockscreen flags the app might set during its first relayout.
private final ArrayMap<AppWindowToken, Integer> mUnknownApps = new ArrayMap<>();
/**
* Notifies that {@param appWindow} has finished resuming.
*/
void notifyAppResumedFinished(@NonNull AppWindowToken appWindow) {
if (mUnknownApps.containsKey(appWindow)
&& mUnknownApps.get(appWindow) == UNKNOWN_STATE_WAITING_RESUME) {
if (DEBUG_UNKNOWN_APP_VISIBILITY) {
Slog.d(TAG, "App resume finished appWindow=" + appWindow);
}
mUnknownApps.put(appWindow, UNKNOWN_STATE_WAITING_RELAYOUT);
}
}