Android 10.0 Activity启动流程源码分析
2020-08-25 本文已影响0人
竖起大拇指
1.startActivity()入口
//Activity.java
/**
* Same as {@link #startActivity(Intent, Bundle)} with no options
* specified.
*
* @param intent The intent to start.
*
* @throws android.content.ActivityNotFoundException
*
* @see #startActivity(Intent, Bundle)
* @see #startActivityForResult
*/
@Override
public void startActivity(Intent intent) {
this.startActivity(intent, null);
}
@Override
public void startActivity(Intent intent, @Nullable Bundle options) {
if (options != null) {
startActivityForResult(intent, -1, options);
} else {
// Note we want to go through this call for compatibility with
// applications that may have overridden the method.
startActivityForResult(intent, -1);
}
}
public void startActivityForResult(@RequiresPermission Intent intent, int requestCode) {
startActivityForResult(intent, requestCode, null);
}
public void startActivityForResult(@RequiresPermission Intent intent, int requestCode,
@Nullable Bundle options) {
if (mParent == null) {
options = transferSpringboardActivityOptions(options);
//注释1
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, this,
intent, requestCode, options);
if (ar != null) {
mMainThread.sendActivityResult(
mToken, mEmbeddedID, requestCode, ar.getResultCode(),
ar.getResultData());
}
if (requestCode >= 0) {
// If this start is requesting a result, we can avoid making
// the activity visible until the result is received. Setting
// this code during onCreate(Bundle savedInstanceState) or onResume() will keep the
// activity hidden during this time, to avoid flickering.
// This can only be done when a result is requested because
// that guarantees we will get information back when the
// activity is finished, no matter what happens to it.
mStartedActivity = true;
}
cancelInputsAndStartExitTransition(options);
// TODO Consider clearing/flushing other event sources and events for child windows.
} else {
if (options != null) {
mParent.startActivityFromChild(this, intent, requestCode, options);
} else {
// Note we want to go through this method for compatibility with
// existing applications that may have overridden it.
mParent.startActivityFromChild(this, intent, requestCode);
}
}
}
Instrumentation流程
在注释1的地方调用了mInstrumentation.execStartActivity方法，代码如下:
//Instrumentation.java
@UnsupportedAppUsage
public ActivityResult execStartActivity(
Context who, IBinder contextThread, IBinder token, Activity target,
Intent intent, int requestCode, Bundle options) {
IApplicationThread whoThread = (IApplicationThread) contextThread;
Uri referrer = target != null ? target.onProvideReferrer() : null;
if (referrer != null) {
intent.putExtra(Intent.EXTRA_REFERRER, referrer);
}
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i<N; i++) {
final ActivityMonitor am = mActivityMonitors.get(i);
ActivityResult result = null;
if (am.ignoreMatchingSpecificIntents()) {
result = am.onStartActivity(intent);
}
if (result != null) {
am.mHits++;
return result;
} else if (am.match(who, null, intent)) {
am.mHits++;
if (am.isBlocking()) {
return requestCode >= 0 ? am.getResult() : null;
}
break;
}
}
}
}
try {
intent.migrateExtraStreamToClipData();
intent.prepareToLeaveProcess(who);
//注释1
int result = ActivityTaskManager.getService()
.startActivity(whoThread, who.getBasePackageName(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()),
token, target != null ? target.mEmbeddedID : null,
requestCode, 0, null, options);
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
throw new RuntimeException("Failure from system", e);
}
return null;
}
ActivityTaskManagerService的流程
ActivityTaskManager拿到了远程服务端的ActivityTaskManagerService,就可以调用远程服务中的方法，其本质还是binder通信。
//ActivityTaskManagerService.java
@Override
public final int startActivity(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {
return startActivityAsUser(caller, callingPackage, intent, resolvedType, resultTo,
resultWho, requestCode, startFlags, profilerInfo, bOptions,
UserHandle.getCallingUserId());
}
@Override
public int startActivityAsUser(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId) {
return startActivityAsUser(caller, callingPackage, intent, resolvedType, resultTo,
resultWho, requestCode, startFlags, profilerInfo, bOptions, userId,
true /*validateIncomingUser*/);
}
int startActivityAsUser(IApplicationThread caller, String callingPackage,
Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId,
boolean validateIncomingUser) {
enforceNotIsolatedCaller("startActivityAsUser");
userId = getActivityStartController().checkTargetUser(userId, validateIncomingUser,
Binder.getCallingPid(), Binder.getCallingUid(), "startActivityAsUser");
//注释1
// TODO: Switch to user app stacks here.
return getActivityStartController().obtainStarter(intent, "startActivityAsUser")
.setCaller(caller)
.setCallingPackage(callingPackage)
.setResolvedType(resolvedType)
.setResultTo(resultTo)
.setResultWho(resultWho)
.setRequestCode(requestCode)
.setStartFlags(startFlags)
.setProfilerInfo(profilerInfo)
.setActivityOptions(bOptions)
.setMayWait(userId)
.execute();
}
经过两次startActivityAsUser的重载调用，最终调用了注释1的getActivityStartController().obtaionStarter的方法得到了一个ActivityStarter对象，通过一系列的链式调用进行参数设置并最终执行了execute方法，下面是ActivityStarter的execute方法的源码:
ActivityStarter的流程
//ActivityStarter.java
/**
* Starts an activity based on the request parameters provided earlier.
* @return The starter result.
*/
int execute() {
try {
// TODO(b/64750076): Look into passing request directly to these methods to allow
// for transactional diffs and preprocessing.
if (mRequest.mayWait) {
return startActivityMayWait(mRequest.caller, mRequest.callingUid,
mRequest.callingPackage, mRequest.realCallingPid, mRequest.realCallingUid,
mRequest.intent, mRequest.resolvedType,
mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,
mRequest.resultWho, mRequest.requestCode, mRequest.startFlags,
mRequest.profilerInfo, mRequest.waitResult, mRequest.globalConfig,
mRequest.activityOptions, mRequest.ignoreTargetSecurity, mRequest.userId,
mRequest.inTask, mRequest.reason,
mRequest.allowPendingRemoteAnimationRegistryLookup,
mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart);
} else {
return startActivity(mRequest.caller, mRequest.intent, mRequest.ephemeralIntent,
mRequest.resolvedType, mRequest.activityInfo, mRequest.resolveInfo,
mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,
mRequest.resultWho, mRequest.requestCode, mRequest.callingPid,
mRequest.callingUid, mRequest.callingPackage, mRequest.realCallingPid,
mRequest.realCallingUid, mRequest.startFlags, mRequest.activityOptions,
mRequest.ignoreTargetSecurity, mRequest.componentSpecified,
mRequest.outActivity, mRequest.inTask, mRequest.reason,
mRequest.allowPendingRemoteAnimationRegistryLookup,
mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart);
}
} finally {
onExecutionComplete();
}
}
由于上面的链式调用setMayWait(userId)的时候mRequest.mayWait已经设置为了true，所以就直接调用startActivityMayWait方法了。ActivityStarter的链式方法:setMayWait
//ActivityStarter.java
ActivityStarter setMayWait(int userId) {
mRequest.mayWait = true;
mRequest.userId = userId;
return this;
}
startActivityMayWait方法源码如下:
private int startActivityMayWait(IApplicationThread caller, int callingUid,
String callingPackage, int requestRealCallingPid, int requestRealCallingUid,
Intent intent, String resolvedType, IVoiceInteractionSession voiceSession,
IVoiceInteractor voiceInteractor, IBinder resultTo, String resultWho, int requestCode,
int startFlags, ProfilerInfo profilerInfo, WaitResult outResult,
Configuration globalConfig, SafeActivityOptions options, boolean ignoreTargetSecurity,
int userId, TaskRecord inTask, String reason,
boolean allowPendingRemoteAnimationRegistryLookup,
PendingIntentRecord originatingPendingIntent, boolean allowBackgroundActivityStart) {
// Refuse possible leaked file descriptors
if (intent != null && intent.hasFileDescriptors()) {
throw new IllegalArgumentException("File descriptors passed in Intent");
}
mSupervisor.getActivityMetricsLogger().notifyActivityLaunching(intent);
boolean componentSpecified = intent.getComponent() != null;
final int realCallingPid = requestRealCallingPid != Request.DEFAULT_REAL_CALLING_PID
? requestRealCallingPid
: Binder.getCallingPid();
final int realCallingUid = requestRealCallingUid != Request.DEFAULT_REAL_CALLING_UID
? requestRealCallingUid
: Binder.getCallingUid();
int callingPid;
if (callingUid >= 0) {
callingPid = -1;
} else if (caller == null) {
callingPid = realCallingPid;
callingUid = realCallingUid;
} else {
callingPid = callingUid = -1;
}
// Save a copy in case ephemeral needs it
final Intent ephemeralIntent = new Intent(intent);
// Don't modify the client's object!
intent = new Intent(intent);
if (componentSpecified
&& !(Intent.ACTION_VIEW.equals(intent.getAction()) && intent.getData() == null)
&& !Intent.ACTION_INSTALL_INSTANT_APP_PACKAGE.equals(intent.getAction())
&& !Intent.ACTION_RESOLVE_INSTANT_APP_PACKAGE.equals(intent.getAction())
&& mService.getPackageManagerInternalLocked()
.isInstantAppInstallerComponent(intent.getComponent())) {
// intercept intents targeted directly to the ephemeral installer the
// ephemeral installer should never be started with a raw Intent; instead
// adjust the intent so it looks like a "normal" instant app launch
intent.setComponent(null /*component*/);
componentSpecified = false;
}
ResolveInfo rInfo = mSupervisor.resolveIntent(intent, resolvedType, userId,
0 /* matchFlags */,
computeResolveFilterUid(
callingUid, realCallingUid, mRequest.filterCallingUid));
if (rInfo == null) {
UserInfo userInfo = mSupervisor.getUserInfo(userId);
if (userInfo != null && userInfo.isManagedProfile()) {
// Special case for managed profiles, if attempting to launch non-cryto aware
// app in a locked managed profile from an unlocked parent allow it to resolve
// as user will be sent via confirm credentials to unlock the profile.
UserManager userManager = UserManager.get(mService.mContext);
boolean profileLockedAndParentUnlockingOrUnlocked = false;
long token = Binder.clearCallingIdentity();
try {
UserInfo parent = userManager.getProfileParent(userId);
profileLockedAndParentUnlockingOrUnlocked = (parent != null)
&& userManager.isUserUnlockingOrUnlocked(parent.id)
&& !userManager.isUserUnlockingOrUnlocked(userId);
} finally {
Binder.restoreCallingIdentity(token);
}
if (profileLockedAndParentUnlockingOrUnlocked) {
rInfo = mSupervisor.resolveIntent(intent, resolvedType, userId,
PackageManager.MATCH_DIRECT_BOOT_AWARE
| PackageManager.MATCH_DIRECT_BOOT_UNAWARE,
computeResolveFilterUid(
callingUid, realCallingUid, mRequest.filterCallingUid));
}
}
}
// Collect information about the target of the Intent.
ActivityInfo aInfo = mSupervisor.resolveActivity(intent, rInfo, startFlags, profilerInfo);
synchronized (mService.mGlobalLock) {
final ActivityStack stack = mRootActivityContainer.getTopDisplayFocusedStack();
stack.mConfigWillChange = globalConfig != null
&& mService.getGlobalConfiguration().diff(globalConfig) != 0;
if (DEBUG_CONFIGURATION) Slog.v(TAG_CONFIGURATION,
"Starting activity when config will change = " + stack.mConfigWillChange);
final long origId = Binder.clearCallingIdentity();
if (aInfo != null &&
(aInfo.applicationInfo.privateFlags
& ApplicationInfo.PRIVATE_FLAG_CANT_SAVE_STATE) != 0 &&
mService.mHasHeavyWeightFeature) {
// This may be a heavy-weight process! Check to see if we already
// have another, different heavy-weight process running.
if (aInfo.processName.equals(aInfo.applicationInfo.packageName)) {
final WindowProcessController heavy = mService.mHeavyWeightProcess;
if (heavy != null && (heavy.mInfo.uid != aInfo.applicationInfo.uid
|| !heavy.mName.equals(aInfo.processName))) {
int appCallingUid = callingUid;
if (caller != null) {
WindowProcessController callerApp =
mService.getProcessController(caller);
if (callerApp != null) {
appCallingUid = callerApp.mInfo.uid;
} else {
Slog.w(TAG, "Unable to find app for caller " + caller
+ " (pid=" + callingPid + ") when starting: "
+ intent.toString());
SafeActivityOptions.abort(options);
return ActivityManager.START_PERMISSION_DENIED;
}
}
IIntentSender target = mService.getIntentSenderLocked(
ActivityManager.INTENT_SENDER_ACTIVITY, "android",
appCallingUid, userId, null, null, 0, new Intent[] { intent },
new String[] { resolvedType }, PendingIntent.FLAG_CANCEL_CURRENT
| PendingIntent.FLAG_ONE_SHOT, null);
Intent newIntent = new Intent();
if (requestCode >= 0) {
// Caller is requesting a result.
newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_HAS_RESULT, true);
}
newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_INTENT,
new IntentSender(target));
heavy.updateIntentForHeavyWeightActivity(newIntent);
newIntent.putExtra(HeavyWeightSwitcherActivity.KEY_NEW_APP,
aInfo.packageName);
newIntent.setFlags(intent.getFlags());
newIntent.setClassName("android",
HeavyWeightSwitcherActivity.class.getName());
intent = newIntent;
resolvedType = null;
caller = null;
callingUid = Binder.getCallingUid();
callingPid = Binder.getCallingPid();
componentSpecified = true;
rInfo = mSupervisor.resolveIntent(intent, null /*resolvedType*/, userId,
0 /* matchFlags */, computeResolveFilterUid(
callingUid, realCallingUid, mRequest.filterCallingUid));
aInfo = rInfo != null ? rInfo.activityInfo : null;
if (aInfo != null) {
aInfo = mService.mAmInternal.getActivityInfoForUser(aInfo, userId);
}
}
}
}
final ActivityRecord[] outRecord = new ActivityRecord[1];
//注释1
int res = startActivity(caller, intent, ephemeralIntent, resolvedType, aInfo, rInfo,
voiceSession, voiceInteractor, resultTo, resultWho, requestCode, callingPid,
callingUid, callingPackage, realCallingPid, realCallingUid, startFlags, options,
ignoreTargetSecurity, componentSpecified, outRecord, inTask, reason,
allowPendingRemoteAnimationRegistryLookup, originatingPendingIntent,
allowBackgroundActivityStart);
Binder.restoreCallingIdentity(origId);
......省略代码........
}
private int startActivity(IApplicationThread caller, Intent intent, Intent ephemeralIntent,
String resolvedType, ActivityInfo aInfo, ResolveInfo rInfo,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid,
String callingPackage, int realCallingPid, int realCallingUid, int startFlags,
SafeActivityOptions options, boolean ignoreTargetSecurity, boolean componentSpecified,
ActivityRecord[] outActivity, TaskRecord inTask, String reason,
boolean allowPendingRemoteAnimationRegistryLookup,
PendingIntentRecord originatingPendingIntent, boolean allowBackgroundActivityStart) {
if (TextUtils.isEmpty(reason)) {
throw new IllegalArgumentException("Need to specify a reason.");
}
mLastStartReason = reason;
mLastStartActivityTimeMs = System.currentTimeMillis();
mLastStartActivityRecord[0] = null;
//注释1
mLastStartActivityResult = startActivity(caller, intent, ephemeralIntent, resolvedType,
aInfo, rInfo, voiceSession, voiceInteractor, resultTo, resultWho, requestCode,
callingPid, callingUid, callingPackage, realCallingPid, realCallingUid, startFlags,
options, ignoreTargetSecurity, componentSpecified, mLastStartActivityRecord,
inTask, allowPendingRemoteAnimationRegistryLookup, originatingPendingIntent,
allowBackgroundActivityStart);
if (outActivity != null) {
// mLastStartActivityRecord[0] is set in the call to startActivity above.
outActivity[0] = mLastStartActivityRecord[0];
}
return getExternalResult(mLastStartActivityResult);
}
private int startActivity(IApplicationThread caller, Intent intent, Intent ephemeralIntent,
String resolvedType, ActivityInfo aInfo, ResolveInfo rInfo,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid,
String callingPackage, int realCallingPid, int realCallingUid, int startFlags,
SafeActivityOptions options,
boolean ignoreTargetSecurity, boolean componentSpecified, ActivityRecord[] outActivity,
TaskRecord inTask, boolean allowPendingRemoteAnimationRegistryLookup,
PendingIntentRecord originatingPendingIntent, boolean allowBackgroundActivityStart) {
............省略代码................
final ActivityStack stack = mRootActivityContainer.getTopDisplayFocusedStack();
// If we are starting an activity that is not from the same uid as the currently resumed
// one, check whether app switches are allowed.
if (voiceSession == null && (stack.getResumedActivity() == null
|| stack.getResumedActivity().info.applicationInfo.uid != realCallingUid)) {
if (!mService.checkAppSwitchAllowedLocked(callingPid, callingUid,
realCallingPid, realCallingUid, "Activity start")) {
if (!(restrictedBgActivity && handleBackgroundActivityAbort(r))) {
mController.addPendingActivityLaunch(new PendingActivityLaunch(r,
sourceRecord, startFlags, stack, callerApp));
}
ActivityOptions.abort(checkedOptions);
return ActivityManager.START_SWITCHES_CANCELED;
}
}
mService.onStartActivitySetDidAppSwitch();
mController.doPendingActivityLaunches(false);
//注释1
final int res = startActivity(r, sourceRecord, voiceSession, voiceInteractor, startFlags,
true /* doResume */, checkedOptions, inTask, outActivity, restrictedBgActivity);
mSupervisor.getActivityMetricsLogger().notifyActivityLaunched(res, outActivity[0]);
return res;
}
//继续重载startActivity方法
private int startActivity(final ActivityRecord r, ActivityRecord sourceRecord,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask,
ActivityRecord[] outActivity, boolean restrictedBgActivity) {
int result = START_CANCELED;
final ActivityStack startedActivityStack;
try {
mService.mWindowManager.deferSurfaceLayout();
//注释1
result = startActivityUnchecked(r, sourceRecord, voiceSession, voiceInteractor,
startFlags, doResume, options, inTask, outActivity, restrictedBgActivity);
} finally {
final ActivityStack currentStack = r.getActivityStack();
startedActivityStack = currentStack != null ? currentStack : mTargetStack;
if (ActivityManager.isStartResultSuccessful(result)) {
if (startedActivityStack != null) {
// If there is no state change (e.g. a resumed activity is reparented to
// top of another display) to trigger a visibility/configuration checking,
// we have to update the configuration for changing to different display.
final ActivityRecord currentTop =
startedActivityStack.topRunningActivityLocked();
if (currentTop != null && currentTop.shouldUpdateConfigForDisplayChanged()) {
mRootActivityContainer.ensureVisibilityAndConfig(
currentTop, currentTop.getDisplayId(),
true /* markFrozenIfConfigChanged */, false /* deferResume */);
}
}
} else {
// If we are not able to proceed, disassociate the activity from the task.
// Leaving an activity in an incomplete state can lead to issues, such as
// performing operations without a window container.
final ActivityStack stack = mStartActivity.getActivityStack();
if (stack != null) {
stack.finishActivityLocked(mStartActivity, RESULT_CANCELED,
null /* intentResultData */, "startActivity", true /* oomAdj */);
}
// Stack should also be detached from display and be removed if it's empty.
if (startedActivityStack != null && startedActivityStack.isAttached()
&& startedActivityStack.numActivities() == 0
&& !startedActivityStack.isActivityTypeHome()) {
startedActivityStack.remove();
}
}
mService.mWindowManager.continueSurfaceLayout();
}
postStartActivityProcessing(r, result, startedActivityStack);
return result;
}
通过三次调用startActivity的重载方法调用，最终到达它的startActivityUnchecked方法,
// Note: This method should only be called from {@link startActivity}.
private int startActivityUnchecked(final ActivityRecord r, ActivityRecord sourceRecord,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask,
ActivityRecord[] outActivity, boolean restrictedBgActivity) {
setInitialState(r, options, inTask, doResume, startFlags, sourceRecord, voiceSession,
voiceInteractor, restrictedBgActivity);
......省略部分代码.........
mTargetStack.startActivityLocked(mStartActivity, topFocused, newTask, mKeepCurTransition,
mOptions);
if (mDoResume) {
final ActivityRecord topTaskActivity =
mStartActivity.getTaskRecord().topRunningActivityLocked();
if (!mTargetStack.isFocusable()
|| (topTaskActivity != null && topTaskActivity.mTaskOverlay
&& mStartActivity != topTaskActivity)) {
// If the activity is not focusable, we can't resume it, but still would like to
// make sure it becomes visible as it starts (this will also trigger entry
// animation). An example of this are PIP activities.
// Also, we don't want to resume activities in a task that currently has an overlay
// as the starting activity just needs to be in the visible paused state until the
// over is removed.
mTargetStack.ensureActivitiesVisibleLocked(mStartActivity, 0, !PRESERVE_WINDOWS);
// Go ahead and tell window manager to execute app transition for this activity
// since the app transition will not be triggered through the resume channel.
mTargetStack.getDisplay().mDisplayContent.executeAppTransition();
} else {
// If the target stack was not previously focusable (previous top running activity
// on that stack was not visible) then any prior calls to move the stack to the
// will not update the focused stack. If starting the new activity now allows the
// task stack to be focusable, then ensure that we now update the focused stack
// accordingly.
if (mTargetStack.isFocusable()
&& !mRootActivityContainer.isTopDisplayFocusedStack(mTargetStack)) {
mTargetStack.moveToFront("startActivityUnchecked");
}
//注释1
mRootActivityContainer.resumeFocusedStacksTopActivities(
mTargetStack, mStartActivity, mOptions);
}
} else if (mStartActivity != null) {
mSupervisor.mRecentTasks.add(mStartActivity.getTaskRecord());
}
mRootActivityContainer.updateUserStack(mStartActivity.mUserId, mTargetStack);
mSupervisor.handleNonResizableTaskIfNeeded(mStartActivity.getTaskRecord(),
preferredWindowingMode, mPreferredDisplayId, mTargetStack);
return START_SUCCESS;
}
这个方法的实现很长，最终调用了mRootActivityContainer.resumeFocusedStacksTopActivities方法，至此启动流程由ActivityStarter走到了RootActivityContainer的resumeFocusedStacksTopActivities方法。
RootActivityContainer的流程
//RootActivityContainer.java
boolean resumeFocusedStacksTopActivities(
ActivityStack targetStack, ActivityRecord target, ActivityOptions targetOptions) {
if (!mStackSupervisor.readyToResume()) {
return false;
}
boolean result = false;
if (targetStack != null && (targetStack.isTopStackOnDisplay()
|| getTopDisplayFocusedStack() == targetStack)) {
result = targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);
}
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
boolean resumedOnDisplay = false;
final ActivityDisplay display = mActivityDisplays.get(displayNdx);
for (int stackNdx = display.getChildCount() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = display.getChildAt(stackNdx);
final ActivityRecord topRunningActivity = stack.topRunningActivityLocked();
if (!stack.isFocusableAndVisible() || topRunningActivity == null) {
continue;
}
if (stack == targetStack) {
// Simply update the result for targetStack because the targetStack had
// already resumed in above. We don't want to resume it again, especially in
// some cases, it would cause a second launch failure if app process was dead.
resumedOnDisplay |= result;
continue;
}
if (display.isTopStack(stack) && topRunningActivity.isState(RESUMED)) {
// Kick off any lingering app transitions form the MoveTaskToFront operation,
// but only consider the top task and stack on that display.
stack.executeAppTransition(targetOptions);
} else {
resumedOnDisplay |= topRunningActivity.makeActiveIfNeeded(target);
}
}
if (!resumedOnDisplay) {
// In cases when there are no valid activities (e.g. device just booted or launcher
// crashed) it's possible that nothing was resumed on a display. Requesting resume
// of top activity in focused stack explicitly will make sure that at least home
// activity is started and resumed, and no recursion occurs.
final ActivityStack focusedStack = display.getFocusedStack();
if (focusedStack != null) {
//注释1
focusedStack.resumeTopActivityUncheckedLocked(target, targetOptions);
}
}
}
return result;
}
在该方法的最后调用了focusedStack.resumeTopActivityUncheckedLocked(target, targetOptions)方法，进入到了ActivityStack
ActivityStack流程
//ActivityStack.java
boolean resumeTopActivityUncheckedLocked(ActivityRecord prev, ActivityOptions options) {
if (mInResumeTopActivity) {
// Don't even start recursing.
return false;
}
boolean result = false;
try {
// Protect against recursion.
mInResumeTopActivity = true;
//注释1
result = resumeTopActivityInnerLocked(prev, options);
// When resuming the top activity, it may be necessary to pause the top activity (for
// example, returning to the lock screen. We suppress the normal pause logic in
// {@link #resumeTopActivityUncheckedLocked}, since the top activity is resumed at the
// end. We call the {@link ActivityStackSupervisor#checkReadyForSleepLocked} again here
// to ensure any necessary pause logic occurs. In the case where the Activity will be
// shown regardless of the lock screen, the call to
// {@link ActivityStackSupervisor#checkReadyForSleepLocked} is skipped.
final ActivityRecord next = topRunningActivityLocked(true /* focusableOnly */);
if (next == null || !next.canTurnScreenOn()) {
checkReadyForSleep();
}
} finally {
mInResumeTopActivity = false;
}
return result;
}
接着调用注释1处的resumeTopActivityInnerLocked方法，源码如下:
//ActivityStack.java
@GuardedBy("mService")
private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {
if (!mService.isBooting() && !mService.isBooted()) {
// Not ready yet!
return false;
}
......省略部分代码
try {
final ClientTransaction transaction =
ClientTransaction.obtain(next.app.getThread(), next.appToken);
// Deliver all pending results.
ArrayList<ResultInfo> a = next.results;
if (a != null) {
final int N = a.size();
if (!next.finishing && N > 0) {
if (DEBUG_RESULTS) Slog.v(TAG_RESULTS,
"Delivering results to " + next + ": " + a);
transaction.addCallback(ActivityResultItem.obtain(a));
}
}
if (next.newIntents != null) {
transaction.addCallback(
NewIntentItem.obtain(next.newIntents, true /* resume */));
}
// Well the app will no longer be stopped.
// Clear app token stopped state in window manager if needed.
next.notifyAppResumed(next.stopped);
EventLog.writeEvent(EventLogTags.AM_RESUME_ACTIVITY, next.mUserId,
System.identityHashCode(next), next.getTaskRecord().taskId,
next.shortComponentName);
next.sleeping = false;
mService.getAppWarningsLocked().onResumeActivity(next);
next.app.setPendingUiCleanAndForceProcessStateUpTo(mService.mTopProcessState);
next.clearOptionsLocked();
transaction.setLifecycleStateRequest(
ResumeActivityItem.obtain(next.app.getReportedProcState(),
getDisplay().mDisplayContent.isNextTransitionForward()));
mService.getLifecycleManager().scheduleTransaction(transaction);
if (DEBUG_STATES) Slog.d(TAG_STATES, "resumeTopActivityLocked: Resumed "
+ next);
} catch (Exception e) {
// Whoops, need to restart this activity!
if (DEBUG_STATES) Slog.v(TAG_STATES, "Resume failed; resetting state to "
+ lastState + ": " + next);
next.setState(lastState, "resumeTopActivityInnerLocked");
// lastResumedActivity being non-null implies there is a lastStack present.
if (lastResumedActivity != null) {
lastResumedActivity.setState(RESUMED, "resumeTopActivityInnerLocked");
}
Slog.i(TAG, "Restarting because process died: " + next);
if (!next.hasBeenLaunched) {
next.hasBeenLaunched = true;
} else if (SHOW_APP_STARTING_PREVIEW && lastFocusedStack != null
&& lastFocusedStack.isTopStackOnDisplay()) {
next.showStartingWindow(null /* prev */, false /* newTask */,
false /* taskSwitch */);
}
mStackSupervisor.startSpecificActivityLocked(next, true, false);
return true;
}
// From this point on, if something goes wrong there is no way
// to recover the activity.
try {
next.completeResumeLocked();
} catch (Exception e) {
// If any exception gets thrown, toss away this
// activity and try the next one.
Slog.w(TAG, "Exception thrown during resume of " + next, e);
requestFinishActivityLocked(next.appToken, Activity.RESULT_CANCELED, null,
"resume-exception", true);
return true;
}
} else {
// Whoops, need to restart this activity!
if (!next.hasBeenLaunched) {
next.hasBeenLaunched = true;
} else {
if (SHOW_APP_STARTING_PREVIEW) {
next.showStartingWindow(null /* prev */, false /* newTask */,
false /* taskSwich */);
}
if (DEBUG_SWITCH) Slog.v(TAG_SWITCH, "Restarting: " + next);
}
if (DEBUG_STATES) Slog.d(TAG_STATES, "resumeTopActivityLocked: Restarting " + next);
//注释1
mStackSupervisor.startSpecificActivityLocked(next, true, true);
}
return true;
}
在方法最后调用了注释1处的mStackSupervisor.startSpecificActivityLocked方法.
ActivityStackSupervisor的流程
//ActivityStackSupervisor.java
void startSpecificActivityLocked(ActivityRecord r, boolean andResume, boolean checkConfig) {
// Is this activity's application already running?
final WindowProcessController wpc =
mService.getProcessController(r.processName, r.info.applicationInfo.uid);
boolean knownToBeDead = false;
if (wpc != null && wpc.hasThread()) {
try {
//注释1
realStartActivityLocked(r, wpc, andResume, checkConfig);
return;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting activity "
+ r.intent.getComponent().flattenToShortString(), e);
}
// If a dead object exception was thrown -- fall through to
// restart the application.
knownToBeDead = true;
}
// Suppress transition until the new activity becomes ready, otherwise the keyguard can
// appear for a short amount of time before the new process with the new activity had the
// ability to set its showWhenLocked flags.
if (getKeyguardController().isKeyguardLocked()) {
r.notifyUnknownVisibilityLaunched();
}
try {
if (Trace.isTagEnabled(TRACE_TAG_ACTIVITY_MANAGER)) {
Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "dispatchingStartProcess:"
+ r.processName);
}
// Post message to start process to avoid possible deadlock of calling into AMS with the
// ATMS lock held.
final Message msg = PooledLambda.obtainMessage(
ActivityManagerInternal::startProcess, mService.mAmInternal, r.processName,
r.info.applicationInfo, knownToBeDead, "activity", r.intent.getComponent());
mService.mH.sendMessage(msg);
} finally {
Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);
}
}
boolean realStartActivityLocked(ActivityRecord r, WindowProcessController proc,
boolean andResume, boolean checkConfig) throws RemoteException {
if (!mRootActivityContainer.allPausedActivitiesComplete()) {
// While there are activities pausing we skipping starting any new activities until
// pauses are complete. NOTE: that we also do this for activities that are starting in
// the paused state because they will first be resumed then paused on the client side.
if (DEBUG_SWITCH || DEBUG_PAUSE || DEBUG_STATES) Slog.v(TAG_PAUSE,
"realStartActivityLocked: Skipping start of r=" + r
+ " some activities pausing...");
return false;
}
final TaskRecord task = r.getTaskRecord();
final ActivityStack stack = task.getStack();
beginDeferResume();
try {
r.startFreezingScreenLocked(proc, 0);
// schedule launch ticks to collect information about slow apps.
r.startLaunchTickingLocked();
r.setProcess(proc);
// Ensure activity is allowed to be resumed after process has set.
if (andResume && !r.canResumeByCompat()) {
andResume = false;
}
if (getKeyguardController().isKeyguardLocked()) {
r.notifyUnknownVisibilityLaunched();
}
// Have the window manager re-evaluate the orientation of the screen based on the new
// activity order. Note that as a result of this, it can call back into the activity
// manager with a new orientation. We don't care about that, because the activity is
// not currently running so we are just restarting it anyway.
if (checkConfig) {
// Deferring resume here because we're going to launch new activity shortly.
// We don't want to perform a redundant launch of the same record while ensuring
// configurations and trying to resume top activity of focused stack.
mRootActivityContainer.ensureVisibilityAndConfig(r, r.getDisplayId(),
false /* markFrozenIfConfigChanged */, true /* deferResume */);
}
if (r.getActivityStack().checkKeyguardVisibility(r, true /* shouldBeVisible */,
true /* isTop */)) {
// We only set the visibility to true if the activity is allowed to be visible
// based on
// keyguard state. This avoids setting this into motion in window manager that is
// later cancelled due to later calls to ensure visible activities that set
// visibility back to false.
r.setVisibility(true);
}
final int applicationInfoUid =
(r.info.applicationInfo != null) ? r.info.applicationInfo.uid : -1;
if ((r.mUserId != proc.mUserId) || (r.appInfo.uid != applicationInfoUid)) {
Slog.wtf(TAG,
"User ID for activity changing for " + r
+ " appInfo.uid=" + r.appInfo.uid
+ " info.ai.uid=" + applicationInfoUid
+ " old=" + r.app + " new=" + proc);
}
r.launchCount++;
r.lastLaunchTime = SystemClock.uptimeMillis();
if (DEBUG_ALL) Slog.v(TAG, "Launching: " + r);
proc.addActivityIfNeeded(r);
final LockTaskController lockTaskController = mService.getLockTaskController();
if (task.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE
|| task.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE_PRIV
|| (task.mLockTaskAuth == LOCK_TASK_AUTH_WHITELISTED
&& lockTaskController.getLockTaskModeState()
== LOCK_TASK_MODE_LOCKED)) {
lockTaskController.startLockTaskMode(task, false, 0 /* blank UID */);
}
try {
if (!proc.hasThread()) {
throw new RemoteException();
}
List<ResultInfo> results = null;
List<ReferrerIntent> newIntents = null;
if (andResume) {
// We don't need to deliver new intents and/or set results if activity is going
// to pause immediately after launch.
results = r.results;
newIntents = r.newIntents;
}
if (DEBUG_SWITCH) Slog.v(TAG_SWITCH,
"Launching: " + r + " icicle=" + r.icicle + " with results=" + results
+ " newIntents=" + newIntents + " andResume=" + andResume);
EventLog.writeEvent(EventLogTags.AM_RESTART_ACTIVITY, r.mUserId,
System.identityHashCode(r), task.taskId, r.shortComponentName);
if (r.isActivityTypeHome()) {
// Home process is the root process of the task.
updateHomeProcess(task.mActivities.get(0).app);
}
mService.getPackageManagerInternalLocked().notifyPackageUse(
r.intent.getComponent().getPackageName(), NOTIFY_PACKAGE_USE_ACTIVITY);
r.sleeping = false;
r.forceNewConfig = false;
mService.getAppWarningsLocked().onStartActivity(r);
r.compat = mService.compatibilityInfoForPackageLocked(r.info.applicationInfo);
// Because we could be starting an Activity in the system process this may not go
// across a Binder interface which would create a new Configuration. Consequently
// we have to always create a new Configuration here.
final MergedConfiguration mergedConfiguration = new MergedConfiguration(
proc.getConfiguration(), r.getMergedOverrideConfiguration());
r.setLastReportedConfiguration(mergedConfiguration);
logIfTransactionTooLarge(r.intent, r.icicle);
// Create activity launch transaction.
final ClientTransaction clientTransaction = ClientTransaction.obtain(
proc.getThread(), r.appToken);
final DisplayContent dc = r.getDisplay().mDisplayContent;
clientTransaction.addCallback(LaunchActivityItem.obtain(new Intent(r.intent),
System.identityHashCode(r), r.info,
// TODO: Have this take the merged configuration instead of separate global
// and override configs.
mergedConfiguration.getGlobalConfiguration(),
mergedConfiguration.getOverrideConfiguration(), r.compat,
r.launchedFromPackage, task.voiceInteractor, proc.getReportedProcState(),
r.icicle, r.persistentState, results, newIntents,
dc.isNextTransitionForward(), proc.createProfilerInfoIfNeeded(),
r.assistToken));
// Set desired final state.
final ActivityLifecycleItem lifecycleItem;
if (andResume) {
lifecycleItem = ResumeActivityItem.obtain(dc.isNextTransitionForward());
} else {
lifecycleItem = PauseActivityItem.obtain();
}
clientTransaction.setLifecycleStateRequest(lifecycleItem);
// Schedule transaction.
//注释1
mService.getLifecycleManager().scheduleTransaction(clientTransaction);
if ((proc.mInfo.privateFlags & ApplicationInfo.PRIVATE_FLAG_CANT_SAVE_STATE) != 0
&& mService.mHasHeavyWeightFeature) {
// This may be a heavy-weight process! Note that the package manager will ensure
// that only activity can run in the main process of the .apk, which is the only
// thing that will be considered heavy-weight.
if (proc.mName.equals(proc.mInfo.packageName)) {
if (mService.mHeavyWeightProcess != null
&& mService.mHeavyWeightProcess != proc) {
Slog.w(TAG, "Starting new heavy weight process " + proc
+ " when already running "
+ mService.mHeavyWeightProcess);
}
mService.setHeavyWeightProcess(r);
}
}
} catch (RemoteException e) {
if (r.launchFailed) {
// This is the second time we failed -- finish activity and give up.
Slog.e(TAG, "Second failure launching "
+ r.intent.getComponent().flattenToShortString() + ", giving up", e);
proc.appDied();
stack.requestFinishActivityLocked(r.appToken, Activity.RESULT_CANCELED, null,
"2nd-crash", false);
return false;
}
// This is the first time we failed -- restart process and
// retry.
r.launchFailed = true;
proc.removeActivity(r);
throw e;
}
} finally {
endDeferResume();
}
r.launchFailed = false;
if (stack.updateLRUListLocked(r)) {
Slog.w(TAG, "Activity " + r + " being launched, but already in LRU list");
}
// TODO(lifecycler): Resume or pause requests are done as part of launch transaction,
// so updating the state should be done accordingly.
if (andResume && readyToResume()) {
// As part of the process of launching, ActivityThread also performs
// a resume.
stack.minimalResumeActivityLocked(r);
} else {
// This activity is not starting in the resumed state... which should look like we asked
// it to pause+stop (but remain visible), and it has done so and reported back the
// current icicle and other state.
if (DEBUG_STATES) Slog.v(TAG_STATES,
"Moving to PAUSED: " + r + " (starting in paused state)");
r.setState(PAUSED, "realStartActivityLocked");
}
// Perform OOM scoring after the activity state is set, so the process can be updated with
// the latest state.
proc.onStartActivity(mService.mTopProcessState, r.info);
// Launch the new version setup screen if needed. We do this -after-
// launching the initial activity (that is, home), so that it can have
// a chance to initialize itself while in the background, making the
// switch back to it faster and look better.
if (mRootActivityContainer.isTopDisplayFocusedStack(stack)) {
mService.getActivityStartController().startSetupActivity();
}
// Update any services we are bound to that might care about whether
// their client may have activities.
if (r.app != null) {
r.app.updateServiceConnectionActivities();
}
return true;
}
上面的方法流程最终会调用注释1处的mService.getLifecycleManager().scheduleTransaction(clientTransaction);mService就是ActivityTaskManagerService，下面我们看它getLifecycleManager方法实现。
//ActivityTaskManagerService.java
@VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)
public ActivityTaskManagerService(Context context) {
mContext = context;
mFactoryTest = FactoryTest.getMode();
mSystemThread = ActivityThread.currentActivityThread();
mUiContext = mSystemThread.getSystemUiContext();
mLifecycleManager = new ClientLifecycleManager();
mInternal = new LocalService();
GL_ES_VERSION = SystemProperties.getInt("ro.opengles.version", GL_ES_VERSION_UNDEFINED);
}
ClientLifecycleManager getLifecycleManager() {
return mLifecycleManager;
}
接下来我们看ClientLifecycleManager的scheduleTransaction方法实现
//ClientLifecycleManager.java
/**
* Schedule a transaction, which may consist of multiple callbacks and a lifecycle request.
* @param transaction A sequence of client transaction items.
* @throws RemoteException
*
* @see ClientTransaction
*/
void scheduleTransaction(ClientTransaction transaction) throws RemoteException {
final IApplicationThread client = transaction.getClient();
transaction.schedule();
if (!(client instanceof Binder)) {
// If client is not an instance of Binder - it's a remote call and at this point it is
// safe to recycle the object. All objects used for local calls will be recycled after
// the transaction is executed on client in ActivityThread.
transaction.recycle();
}
}
ClientTransaction的流程
scheduleTransaction方法很简单，核心代码就是transaction.schedule,transaction就是从ActivityStackSupervisor的realStartActivityLocked方法传递过来的ClientTransaction，下面我们看它的schedule方法实现:
//ClientTransaction.java
/** Target client. */
private IApplicationThread mClient;
/** Obtain an instance initialized with provided params. */
public static ClientTransaction obtain(IApplicationThread client, IBinder activityToken) {
ClientTransaction instance = ObjectPool.obtain(ClientTransaction.class);
if (instance == null) {
instance = new ClientTransaction();
}
instance.mClient = client;
instance.mActivityToken = activityToken;
return instance;
}
/**
* Schedule the transaction after it was initialized. It will be send to client and all its
* individual parts will be applied in the following sequence:
* 1. The client calls {@link #preExecute(ClientTransactionHandler)}, which triggers all work
* that needs to be done before actually scheduling the transaction for callbacks and
* lifecycle state request.
* 2. The transaction message is scheduled.
* 3. The client calls {@link TransactionExecutor#execute(ClientTransaction)}, which executes
* all callbacks and necessary lifecycle transitions.
*/
public void schedule() throws RemoteException {
mClient.scheduleTransaction(this);
}
mClient就是ClientTransaction的成员变量IApplicationThread,已经在ActivityStackSupervisor的realStartActivityLocked方法中给赋值了，
// Create activity launch transaction.
final ClientTransaction clientTransaction = ClientTransaction.obtain(
proc.getThread(), r.appToken);
看到这里也就很清楚了mClient就是proc.getThread()，就是ActivityThread的内部类ApplicationThread，本质上他是一个binder ，它实现了IApplicationThread接口，那么 mClient.scheduleTransaction方法的调用实际上就是调用了ApplicationThread的scheduleTransaction方法，从而实现了跨进程调用。
ApplicationThread的流程
下面我们看scheduleTransaction方法的具体实现:
//ApplicationThread.java
@Override
public void scheduleTransaction(ClientTransaction transaction) throws RemoteException {
ActivityThread.this.scheduleTransaction(transaction);
}
ActivityThread的流程
下面我们看ActivityThread的scheduleTransaction方法实现
//ClientTransactionHandler .java
public abstract class ClientTransactionHandler {
// Schedule phase related logic and handlers.
/** Prepare and schedule transaction for execution. */
void scheduleTransaction(ClientTransaction transaction) {
transaction.preExecute(this);
sendMessage(ActivityThread.H.EXECUTE_TRANSACTION, transaction);
}
....省略其他代码...........
}
我们发现它发送了一个EXECUTE_TRANSACTION类型的消息，Handler内部处理如下:
//ActivityThread内部类H
class H extends Handler{
...........省略..................
case EXECUTE_TRANSACTION:
final ClientTransaction transaction = (ClientTransaction) msg.obj;
mTransactionExecutor.execute(transaction);
if (isSystem()) {
// Client transactions inside system process are recycled on the client side
// instead of ClientLifecycleManager to avoid being cleared before this
// message is handled.
transaction.recycle();
}
// TODO(lifecycler): Recycle locally scheduled transactions.
break;
.............省略...................
}
TransactionExecutor的流程
execute方法，源码如下:
//TransactionExecutor.java
/**
* Resolve transaction.
* First all callbacks will be executed in the order they appear in the list. If a callback
* requires a certain pre- or post-execution state, the client will be transitioned accordingly.
* Then the client will cycle to the final lifecycle state if provided. Otherwise, it will
* either remain in the initial state, or last state needed by a callback.
*/
public void execute(ClientTransaction transaction) {
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "Start resolving transaction");
final IBinder token = transaction.getActivityToken();
if (token != null) {
final Map<IBinder, ClientTransactionItem> activitiesToBeDestroyed =
mTransactionHandler.getActivitiesToBeDestroyed();
final ClientTransactionItem destroyItem = activitiesToBeDestroyed.get(token);
if (destroyItem != null) {
if (transaction.getLifecycleStateRequest() == destroyItem) {
// It is going to execute the transaction that will destroy activity with the
// token, so the corresponding to-be-destroyed record can be removed.
activitiesToBeDestroyed.remove(token);
}
if (mTransactionHandler.getActivityClient(token) == null) {
// The activity has not been created but has been requested to destroy, so all
// transactions for the token are just like being cancelled.
Slog.w(TAG, tId(transaction) + "Skip pre-destroyed transaction:\n"
+ transactionToString(transaction, mTransactionHandler));
return;
}
}
}
if (DEBUG_RESOLVER) Slog.d(TAG, transactionToString(transaction, mTransactionHandler));
//注释1
executeCallbacks(transaction);
executeLifecycleState(transaction);
mPendingActions.clear();
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "End resolving transaction");
}
/** Cycle through all states requested by callbacks and execute them at proper times. */
@VisibleForTesting
public void executeCallbacks(ClientTransaction transaction) {
final List<ClientTransactionItem> callbacks = transaction.getCallbacks();
if (callbacks == null || callbacks.isEmpty()) {
// No callbacks to execute, return early.
return;
}
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "Resolving callbacks in transaction");
final IBinder token = transaction.getActivityToken();
ActivityClientRecord r = mTransactionHandler.getActivityClient(token);
// In case when post-execution state of the last callback matches the final state requested
// for the activity in this transaction, we won't do the last transition here and do it when
// moving to final state instead (because it may contain additional parameters from server).
final ActivityLifecycleItem finalStateRequest = transaction.getLifecycleStateRequest();
final int finalState = finalStateRequest != null ? finalStateRequest.getTargetState()
: UNDEFINED;
// Index of the last callback that requests some post-execution state.
final int lastCallbackRequestingState = lastCallbackRequestingState(transaction);
final int size = callbacks.size();
for (int i = 0; i < size; ++i) {
final ClientTransactionItem item = callbacks.get(i);
if (DEBUG_RESOLVER) Slog.d(TAG, tId(transaction) + "Resolving callback: " + item);
final int postExecutionState = item.getPostExecutionState();
final int closestPreExecutionState = mHelper.getClosestPreExecutionState(r,
item.getPostExecutionState());
if (closestPreExecutionState != UNDEFINED) {
cycleToPath(r, closestPreExecutionState, transaction);
}
//注释1
item.execute(mTransactionHandler, token, mPendingActions);
item.postExecute(mTransactionHandler, token, mPendingActions);
if (r == null) {
// Launch activity request will create an activity record.
r = mTransactionHandler.getActivityClient(token);
}
if (postExecutionState != UNDEFINED && r != null) {
// Skip the very last transition and perform it by explicit state request instead.
final boolean shouldExcludeLastTransition =
i == lastCallbackRequestingState && finalState == postExecutionState;
cycleToPath(r, postExecutionState, shouldExcludeLastTransition, transaction);
}
}
}
继续查看注释1处的item.execute(mTransactionHandler, token, mPendingActions)方法，item就是ClientTransactionItem.
//ClientTransactionItem.java
/**
* A callback message to a client that can be scheduled and executed.
* Examples of these might be activity configuration change, multi-window mode change, activity
* result delivery etc.
*
* @see ClientTransaction
* @see com.android.server.am.ClientLifecycleManager
* @hide
*/
public abstract class ClientTransactionItem implements BaseClientRequest, Parcelable {
/** Get the state that must follow this callback. */
@LifecycleState
public int getPostExecutionState() {
return UNDEFINED;
}
// Parcelable
@Override
public int describeContents() {
return 0;
}
}
它是一个抽象类，我们需要找到它的实现类，我们是否还记得在ActivityStackSupervisor的realStartActivityLocked方法中有这么一句clientTransaction.addCallback.
//ActivityStackSupervisor.realStartActivityLocked()
// Create activity launch transaction.
final ClientTransaction clientTransaction = ClientTransaction.obtain(
proc.getThread(), r.appToken);
final DisplayContent dc = r.getDisplay().mDisplayContent;
//注释1
clientTransaction.addCallback(LaunchActivityItem.obtain(new Intent(r.intent),
System.identityHashCode(r), r.info,
// TODO: Have this take the merged configuration instead of separate global
// and override configs.
mergedConfiguration.getGlobalConfiguration(),
mergedConfiguration.getOverrideConfiguration(), r.compat,
r.launchedFromPackage, task.voiceInteractor, proc.getReportedProcState(),
r.icicle, r.persistentState, results, newIntents,
dc.isNextTransitionForward(), proc.createProfilerInfoIfNeeded(),
r.assistToken));
注释1出现的LanuchActivityItem就是ClientTransactionItem的具体实现类，那么我们查看它的execute方法实现：
//LaunchActivityItem.java
@Override
public void execute(ClientTransactionHandler client, IBinder token,
PendingTransactionActions pendingActions) {
Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
ActivityClientRecord r = new ActivityClientRecord(token, mIntent, mIdent, mInfo,
mOverrideConfig, mCompatInfo, mReferrer, mVoiceInteractor, mState, mPersistentState,
mPendingResults, mPendingNewIntents, mIsForward,
mProfilerInfo, client, mAssistToken);
//注释1
client.handleLaunchActivity(r, pendingActions, null /* customIntent */);
Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);
}
我们只看关键部分注释1的client.handleLaunchActivity,client就是TransactionExecutor的私有变量mTransactionHandler,我们看以下它是在什么时候出事话的:
//TransactionExecutor.java
public class TransactionExecutor {
private static final boolean DEBUG_RESOLVER = false;
private static final String TAG = "TransactionExecutor";
private ClientTransactionHandler mTransactionHandler;
private PendingTransactionActions mPendingActions = new PendingTransactionActions();
private TransactionExecutorHelper mHelper = new TransactionExecutorHelper();
/** Initialize an instance with transaction handler, that will execute all requested actions. */
public TransactionExecutor(ClientTransactionHandler clientTransactionHandler) {
mTransactionHandler = clientTransactionHandler;
}
......省略.............
}
通过构造方法传进来的，那么TransactionExecutor是何时实列化的，通过查找发现，在ActivityThread类有这么一行
//ActivityThread.java
public final class ActivityThread extends ClientTransactionHandler {
.....................
// An executor that performs multi-step transactions.
private final TransactionExecutor mTransactionExecutor = new TransactionExecutor(this);
..................
}
而ActivityThread继承了ClientTransactionHandler，因此client.handleLaunchActivity方法执行的就是ActivityThrad的handleLaunchActivity方法，下面我们查看下handleLaunchActivity方法:
//ActivityThread.java
/**
* Extended implementation of activity launch. Used when server requests a launch or relaunch.
*/
@Override
public Activity handleLaunchActivity(ActivityClientRecord r,
PendingTransactionActions pendingActions, 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
if (!ThreadedRenderer.sRendererDisabled
&& (r.activityInfo.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0) {
HardwareRenderer.preload();
}
WindowManagerGlobal.initialize();
// Hint the GraphicsEnvironment that an activity is launching on the process.
GraphicsEnvironment.hintActivityLaunch();
//注释1
final Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
reportSizeConfigurations(r);
if (!r.activity.mFinished && pendingActions != null) {
pendingActions.setOldState(r.state);
pendingActions.setRestoreInstanceState(true);
pendingActions.setCallOnPostCreate(true);
}
} else {
// If there was an error, for any reason, tell the activity manager to stop us.
try {
ActivityTaskManager.getService()
.finishActivity(r.token, Activity.RESULT_CANCELED, null,
Activity.DONT_FINISH_TASK_WITH_ACTIVITY);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
return a;
}
我们看注释1处的performLaunchActivity方法，源码如下:
//ActivityThread.java
/** Core implementation of activity launch. */
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
ActivityInfo aInfo = r.activityInfo;
if (r.packageInfo == null) {
r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
Context.CONTEXT_INCLUDE_CODE);
}
ComponentName component = r.intent.getComponent();
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);
}
//注释1:上下文创建
ContextImpl appContext = createBaseContextForActivity(r);
Activity activity = null;
try {
//注释2：Activity的创建
java.lang.ClassLoader cl = appContext.getClassLoader();
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
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 {
//注释3:Application的创建
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
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) {
CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
Configuration config = new Configuration(mCompatConfiguration);
if (r.overrideConfig != null) {
config.updateFrom(r.overrideConfig);
}
if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "
+ r.activityInfo.name + " with config " + config);
Window window = null;
if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {
window = r.mPendingRemoveWindow;
r.mPendingRemoveWindow = null;
r.mPendingRemoveWindowManager = null;
}
appContext.setOuterContext(activity);
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, r.configCallback,
r.assistToken);
if (customIntent != null) {
activity.mIntent = customIntent;
}
r.lastNonConfigurationInstances = null;
checkAndBlockForNetworkAccess();
activity.mStartedActivity = false;
int theme = r.activityInfo.getThemeResource();
if (theme != 0) {
activity.setTheme(theme);
}
activity.mCalled = false;
if (r.isPersistable()) {
//注释4：Activity的onCreate方法的执行
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.setState(ON_CREATE);
// updatePendingActivityConfiguration() reads from mActivities to update
// ActivityClientRecord which runs in a different thread. Protect modifications to
// mActivities to avoid race.
synchronized (mResourcesManager) {
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;
}
在注释4是onCreate方法真正被执行的地方，我们继续看Instrumentation的callActivityOnCreate方法
//Instrumentation.java
/**
* Perform calling of an activity's {@link Activity#onCreate}
* 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
* @param persistentState The previously persisted state (or null)
*/
public void callActivityOnCreate(Activity activity, Bundle icicle,
PersistableBundle persistentState) {
prePerformCreate(activity);
//注释1
activity.performCreate(icicle, persistentState);
postPerformCreate(activity);
}
注释1处activity.performCreate方法执行，继续看performCreate方法的源码实现:
final void performCreate(Bundle icicle) {
performCreate(icicle, null);
}
@UnsupportedAppUsage
final void performCreate(Bundle icicle, PersistableBundle persistentState) {
dispatchActivityPreCreated(icicle);
mCanEnterPictureInPicture = true;
restoreHasCurrentPermissionRequest(icicle);
if (persistentState != null) {
onCreate(icicle, persistentState);
} else {
onCreate(icicle);
}
writeEventLog(LOG_AM_ON_CREATE_CALLED, "performCreate");
mActivityTransitionState.readState(icicle);
mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(
com.android.internal.R.styleable.Window_windowNoDisplay, false);
mFragments.dispatchActivityCreated();
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
dispatchActivityPostCreated(icicle);
}
最终我们的Activity的onCreate方法被执行了，截至目前关于Android10.0 Activity的启动流程就分析完了。
