android Activity启动过程(四)startActivityUncheckedLocked
final int startActivityUncheckedLocked(ActivityRecord r, ActivityRecord sourceRecord,
IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor, int startFlags,
boolean doResume, Bundle options, TaskRecord inTask) {
final Intent intent = r.intent;
final int callingUid = r.launchedFromUid; // In some flows in to this function, we retrieve the task record and hold on to it
// without a lock before calling back in to here... so the task at this point may
// not actually be in recents. Check for that, and if it isn't in recents just
// consider it invalid.
if (inTask != null && !inTask.inRecents) {
Slog.w(TAG, "Starting activity in task not in recents: " + inTask);
inTask = null;
} final boolean launchSingleTop = r.launchMode == ActivityInfo.LAUNCH_SINGLE_TOP;
final boolean launchSingleInstance = r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE;
final boolean launchSingleTask = r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK; int launchFlags = intent.getFlags();
if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_DOCUMENT) != 0 &&
(launchSingleInstance || launchSingleTask)) {
// We have a conflict between the Intent and the Activity manifest, manifest wins.
Slog.i(TAG, "Ignoring FLAG_ACTIVITY_NEW_DOCUMENT, launchMode is " +
"\"singleInstance\" or \"singleTask\"");
launchFlags &=
~(Intent.FLAG_ACTIVITY_NEW_DOCUMENT | Intent.FLAG_ACTIVITY_MULTIPLE_TASK);
} else {
switch (r.info.documentLaunchMode) {
case ActivityInfo.DOCUMENT_LAUNCH_NONE:
break;
case ActivityInfo.DOCUMENT_LAUNCH_INTO_EXISTING:
launchFlags |= Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
break;
case ActivityInfo.DOCUMENT_LAUNCH_ALWAYS:
launchFlags |= Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
break;
case ActivityInfo.DOCUMENT_LAUNCH_NEVER:
launchFlags &= ~Intent.FLAG_ACTIVITY_MULTIPLE_TASK;
break;
}
} final boolean launchTaskBehind = r.mLaunchTaskBehind
&& !launchSingleTask && !launchSingleInstance
&& (launchFlags & Intent.FLAG_ACTIVITY_NEW_DOCUMENT) != 0; if (r.resultTo != null && (launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
// For whatever reason this activity is being launched into a new
// task... yet the caller has requested a result back. Well, that
// is pretty messed up, so instead immediately send back a cancel
// and let the new task continue launched as normal without a
// dependency on its originator.
Slog.w(TAG, "Activity is launching as a new task, so cancelling activity result.");
r.resultTo.task.stack.sendActivityResultLocked(-1,
r.resultTo, r.resultWho, r.requestCode,
Activity.RESULT_CANCELED, null);
r.resultTo = null;
} if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_DOCUMENT) != 0 && r.resultTo == null) {
launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
} // If we are actually going to launch in to a new task, there are some cases where
// we further want to do multiple task.
if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
if (launchTaskBehind
|| r.info.documentLaunchMode == ActivityInfo.DOCUMENT_LAUNCH_ALWAYS) {
launchFlags |= Intent.FLAG_ACTIVITY_MULTIPLE_TASK;
}
} // We'll invoke onUserLeaving before onPause only if the launching
// activity did not explicitly state that this is an automated launch.
mUserLeaving = (launchFlags & Intent.FLAG_ACTIVITY_NO_USER_ACTION) == 0;
if (DEBUG_USER_LEAVING) Slog.v(TAG, "startActivity() => mUserLeaving=" + mUserLeaving); // If the caller has asked not to resume at this point, we make note
// of this in the record so that we can skip it when trying to find
// the top running activity.
if (!doResume) {
r.delayedResume = true;
} //如果从Launcher程序启动应用，launchFlags为 FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
//否则一般情况下launcheFlags为0，除非启动Activity时设置了特殊的flag
//启动Activity时默认不会设置FLAG_ACTIVITY_PREVIOUS_IS_TOP
//故此notTop默认情况下会是null ActivityRecord notTop =
(launchFlags & Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP) != 0 ? r : null; // If the onlyIfNeeded flag is set, then we can do this if the activity
// being launched is the same as the one making the call... or, as
// a special case, if we do not know the caller then we count the
// current top activity as the caller.
//START_FLAG_ONLY_IF_NEEDED表示只有在需要的时候才启动目标Activity。也就是说如果调用者和被启动的是一个，那么就没有必要去进行重复的步骤了
if ((startFlags&ActivityManager.START_FLAG_ONLY_IF_NEEDED) != 0) {
//默认情况下这里的代码不会执行
ActivityRecord checkedCaller = sourceRecord;
if (checkedCaller == null) {
checkedCaller = getFocusedStack().topRunningNonDelayedActivityLocked(notTop);
}
if (!checkedCaller.realActivity.equals(r.realActivity)) {
// Caller is not the same as launcher, so always needed.
startFlags &= ~ActivityManager.START_FLAG_ONLY_IF_NEEDED;
}
} boolean addingToTask = false;
TaskRecord reuseTask = null; // If the caller is not coming from another activity, but has given us an
// explicit task into which they would like us to launch the new activity,
// then let's see about doing that.
/*
* 如果调用者不是来自另一个activity（不是在activity中调用startActivity）,
* 但是给了我们用于放入新activity的一个明确的task，将执行下面代码
*
* 我们往上追溯，发现inTask是 中 ActivityManagerService.startActivityAsUser()方法传递的null，
* 所以if里面的不会执行
*/
if (sourceRecord == null && inTask != null && inTask.stack != null) {
final Intent baseIntent = inTask.getBaseIntent();
final ActivityRecord root = inTask.getRootActivity();
if (baseIntent == null) {
ActivityOptions.abort(options);
throw new IllegalArgumentException("Launching into task without base intent: "
+ inTask);
} // If this task is empty, then we are adding the first activity -- it
// determines the root, and must be launching as a NEW_TASK.
if (launchSingleInstance || launchSingleTask) {
if (!baseIntent.getComponent().equals(r.intent.getComponent())) {
ActivityOptions.abort(options);
throw new IllegalArgumentException("Trying to launch singleInstance/Task "
+ r + " into different task " + inTask);
}
if (root != null) {
ActivityOptions.abort(options);
throw new IllegalArgumentException("Caller with inTask " + inTask
+ " has root " + root + " but target is singleInstance/Task");
}
} // If task is empty, then adopt the interesting intent launch flags in to the
// activity being started.
if (root == null) {
final int flagsOfInterest = Intent.FLAG_ACTIVITY_NEW_TASK
| Intent.FLAG_ACTIVITY_MULTIPLE_TASK | Intent.FLAG_ACTIVITY_NEW_DOCUMENT
| Intent.FLAG_ACTIVITY_RETAIN_IN_RECENTS;
launchFlags = (launchFlags&~flagsOfInterest)
| (baseIntent.getFlags()&flagsOfInterest);
intent.setFlags(launchFlags);
inTask.setIntent(r);
addingToTask = true; // If the task is not empty and the caller is asking to start it as the root
// of a new task, then we don't actually want to start this on the task. We
// will bring the task to the front, and possibly give it a new intent.
} else if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
addingToTask = false; } else {
addingToTask = true;
} reuseTask = inTask;
} else {
inTask = null;
} //根据activity的设置，如果满足下列条件，将launchFlags置为FLAG_ACTIVITY_NEW_TASK
if (inTask == null) {
if (sourceRecord == null) {
// This activity is not being started from another... in this
// case we -always- start a new task.
//如果调用者为null，将launchFlags置为 创建一个新task
if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) == 0 && inTask == null) {
Slog.w(TAG, "startActivity called from non-Activity context; forcing " +
"Intent.FLAG_ACTIVITY_NEW_TASK for: " + intent);
launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
}
} else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
// The original activity who is starting us is running as a single
// instance... this new activity it is starting must go on its
// own task.
launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
} else if (launchSingleInstance || launchSingleTask) {
// The activity being started is a single instance... it always
// gets launched into its own task.
launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
}
} ActivityInfo newTaskInfo = null;
Intent newTaskIntent = null;
ActivityStack sourceStack;
if (sourceRecord != null) {
if (sourceRecord.finishing) {
// If the source is finishing, we can't further count it as our source. This
// is because the task it is associated with may now be empty and on its way out,
// so we don't want to blindly throw it in to that task. Instead we will take
// the NEW_TASK flow and try to find a task for it. But save the task information
// so it can be used when creating the new task.
if ((launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) == 0) {
Slog.w(TAG, "startActivity called from finishing " + sourceRecord
+ "; forcing " + "Intent.FLAG_ACTIVITY_NEW_TASK for: " + intent);
launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
newTaskInfo = sourceRecord.info;
newTaskIntent = sourceRecord.task.intent;
}
sourceRecord = null;
sourceStack = null;
} else {
sourceStack = sourceRecord.task.stack;
}
} else {
sourceStack = null;
} boolean movedHome = false;
ActivityStack targetStack; intent.setFlags(launchFlags); // We may want to try to place the new activity in to an existing task. We always
// do this if the target activity is singleTask or singleInstance; we will also do
// this if NEW_TASK has been requested, and there is not an additional qualifier telling
// us to still place it in a new task: multi task, always doc mode, or being asked to
// launch this as a new task behind the current one.
/*
* 我们尝试将新的activity放在一个现有的任务中。但是如果activity被要求是singleTask或者singleInstance，
* 我们会将activity放入一个新的task中.下面的if中主要处理将目标进程置于栈顶，然后将目标activity显示
*/
if (((launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
(launchFlags & Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
|| launchSingleInstance || launchSingleTask) {
// If bring to front is requested, and no result is requested and we have not
// been given an explicit task to launch in to, and
// we can find a task that was started with this same
// component, then instead of launching bring that one to the front.
//如果被开启的activity不是需要开启新的task，而是single instance或者singleTask，
if (inTask == null && r.resultTo == null) {
// See if there is a task to bring to the front. If this is
// a SINGLE_INSTANCE activity, there can be one and only one
// instance of it in the history, and it is always in its own
// unique task, so we do a special search.
//检查此activity是否已经开启了SINGLE_INSTANCE
//findTaskLocked()方法用于查找目标activity所在的task
ActivityRecord intentActivity = !launchSingleInstance ?
findTaskLocked(r) : findActivityLocked(intent, r.info);
if (intentActivity != null) {
if (isLockTaskModeViolation(intentActivity.task)) {
showLockTaskToast();
Slog.e(TAG, "startActivityUnchecked: Attempt to violate Lock Task Mode");
return ActivityManager.START_RETURN_LOCK_TASK_MODE_VIOLATION;
}
if (r.task == null) {
r.task = intentActivity.task;
}
targetStack = intentActivity.task.stack;
targetStack.mLastPausedActivity = null;
if (DEBUG_TASKS) Slog.d(TAG, "Bring to front target: " + targetStack
+ " from " + intentActivity);
targetStack.moveToFront();
if (intentActivity.task.intent == null) {
// This task was started because of movement of
// the activity based on affinity... now that we
// are actually launching it, we can assign the
// base intent.
intentActivity.task.setIntent(r);
}
// If the target task is not in the front, then we need
// to bring it to the front... except... well, with
// SINGLE_TASK_LAUNCH it's not entirely clear. We'd like
// to have the same behavior as if a new instance was
// being started, which means not bringing it to the front
// if the caller is not itself in the front.
//如果目标不在栈顶，我们需要把它放到栈顶
final ActivityStack lastStack = getLastStack();
ActivityRecord curTop = lastStack == null?
null : lastStack.topRunningNonDelayedActivityLocked(notTop);
if (curTop != null && (curTop.task != intentActivity.task ||
curTop.task != lastStack.topTask())) {
r.intent.addFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
if (sourceRecord == null || (sourceStack.topActivity() != null &&
sourceStack.topActivity().task == sourceRecord.task)) {
// We really do want to push this one into the
// user's face, right now.
if (launchTaskBehind && sourceRecord != null) {
intentActivity.setTaskToAffiliateWith(sourceRecord.task);
}
movedHome = true;
targetStack.moveTaskToFrontLocked(intentActivity.task, r, options);
if ((launchFlags &
(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_TASK_ON_HOME))
== (FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_TASK_ON_HOME)) {
// Caller wants to appear on home activity.
intentActivity.task.setTaskToReturnTo(HOME_ACTIVITY_TYPE);
}
options = null;
}
}
// If the caller has requested that the target task be
// reset, then do so.
if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {
intentActivity = targetStack.resetTaskIfNeededLocked(intentActivity, r);
}
if ((startFlags&ActivityManager.START_FLAG_ONLY_IF_NEEDED) != 0) {
// We don't need to start a new activity, and
// the client said not to do anything if that
// is the case, so this is it! And for paranoia, make
// sure we have correctly resumed the top activity.
if (doResume) {
resumeTopActivitiesLocked(targetStack, null, options);
} else {
ActivityOptions.abort(options);
}
return ActivityManager.START_RETURN_INTENT_TO_CALLER;
}
if ((launchFlags &
(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK))
== (Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK)) {
// The caller has requested to completely replace any
// existing task with its new activity. Well that should
// not be too hard...
reuseTask = intentActivity.task;
reuseTask.performClearTaskLocked();
reuseTask.setIntent(r);
} else if ((launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0
|| launchSingleInstance || launchSingleTask) {
//将task中位于目标activity上面的其他activitys清理掉
// In this situation we want to remove all activities
// from the task up to the one being started. In most
// cases this means we are resetting the task to its
// initial state.
ActivityRecord top =
intentActivity.task.performClearTaskLocked(r, launchFlags);
if (top != null) {
if (top.frontOfTask) {
// Activity aliases may mean we use different
// intents for the top activity, so make sure
// the task now has the identity of the new
// intent.
top.task.setIntent(r);
}
ActivityStack.logStartActivity(EventLogTags.AM_NEW_INTENT,
r, top.task);
top.deliverNewIntentLocked(callingUid, r.intent);
} else {
// A special case: we need to
// start the activity because it is not currently
// running, and the caller has asked to clear the
// current task to have this activity at the top.
addingToTask = true;
// Now pretend like this activity is being started
// by the top of its task, so it is put in the
// right place.
sourceRecord = intentActivity;
}
} else if (r.realActivity.equals(intentActivity.task.realActivity)) {
// In this case the top activity on the task is the
// same as the one being launched, so we take that
// as a request to bring the task to the foreground.
// If the top activity in the task is the root
// activity, deliver this new intent to it if it
// desires.
if (((launchFlags&Intent.FLAG_ACTIVITY_SINGLE_TOP) != 0 || launchSingleTop)
&& intentActivity.realActivity.equals(r.realActivity)) {
ActivityStack.logStartActivity(EventLogTags.AM_NEW_INTENT, r,
intentActivity.task);
if (intentActivity.frontOfTask) {
intentActivity.task.setIntent(r);
}
intentActivity.deliverNewIntentLocked(callingUid, r.intent);
} else if (!r.intent.filterEquals(intentActivity.task.intent)) {
// In this case we are launching the root activity
// of the task, but with a different intent. We
// should start a new instance on top.
addingToTask = true;
sourceRecord = intentActivity;
}
} else if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) == 0) {
// In this case an activity is being launched in to an
// existing task, without resetting that task. This
// is typically the situation of launching an activity
// from a notification or shortcut. We want to place
// the new activity on top of the current task.
addingToTask = true;
sourceRecord = intentActivity;
} else if (!intentActivity.task.rootWasReset) {
// In this case we are launching in to an existing task
// that has not yet been started from its front door.
// The current task has been brought to the front.
// Ideally, we'd probably like to place this new task
// at the bottom of its stack, but that's a little hard
// to do with the current organization of the code so
// for now we'll just drop it.
intentActivity.task.setIntent(r);
}
if (!addingToTask && reuseTask == null) {
// We didn't do anything... but it was needed (a.k.a., client
// don't use that intent!) And for paranoia, make
// sure we have correctly resumed the top activity.
if (doResume) {
targetStack.resumeTopActivityLocked(null, options);
} else {
ActivityOptions.abort(options);
}
return ActivityManager.START_TASK_TO_FRONT;
}
}
}
} //String uri = r.intent.toURI();
//Intent intent2 = new Intent(uri);
//Slog.i(TAG, "Given intent: " + r.intent);
//Slog.i(TAG, "URI is: " + uri);
//Slog.i(TAG, "To intent: " + intent2); if (r.packageName != null) {
// If the activity being launched is the same as the one currently
// at the top, then we need to check if it should only be launched
// once.
//如果被启动的Activity正好是栈顶的Activity，
//并且被启动的Activity启动模式是singleTop或者singleTask，
//则不用将新的ActivityRecord加入到栈里
//top Activity为Launcher应用的Activity
ActivityStack topStack = getFocusedStack();
ActivityRecord top = topStack.topRunningNonDelayedActivityLocked(notTop);
//当前处于堆栈顶端的task
if (top != null && r.resultTo == null) {
if (top.realActivity.equals(r.realActivity) && top.userId == r.userId) {
if (top.app != null && top.app.thread != null) {
if ((launchFlags & Intent.FLAG_ACTIVITY_SINGLE_TOP) != 0
|| launchSingleTop || launchSingleTask) {
ActivityStack.logStartActivity(EventLogTags.AM_NEW_INTENT, top,
top.task);
// For paranoia, make sure we have correctly
// resumed the top activity.
topStack.mLastPausedActivity = null;
if (doResume) {
resumeTopActivitiesLocked();
}
ActivityOptions.abort(options);
if ((startFlags&ActivityManager.START_FLAG_ONLY_IF_NEEDED) != 0) {
// We don't need to start a new activity, and
// the client said not to do anything if that
// is the case, so this is it!
return ActivityManager.START_RETURN_INTENT_TO_CALLER;
}
top.deliverNewIntentLocked(callingUid, r.intent);
return ActivityManager.START_DELIVERED_TO_TOP;
}
}
}
} } else {
if (r.resultTo != null) {
r.resultTo.task.stack.sendActivityResultLocked(-1, r.resultTo, r.resultWho,
r.requestCode, Activity.RESULT_CANCELED, null);
}
ActivityOptions.abort(options);
//包名为空，直接返回，没有找到
return ActivityManager.START_CLASS_NOT_FOUND;
} boolean newTask = false;
boolean keepCurTransition = false; TaskRecord taskToAffiliate = launchTaskBehind && sourceRecord != null ?
sourceRecord.task : null; // Should this be considered a new task?
if (r.resultTo == null && inTask == null && !addingToTask
&& (launchFlags & Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
if (isLockTaskModeViolation(reuseTask)) {
Slog.e(TAG, "Attempted Lock Task Mode violation r=" + r);
return ActivityManager.START_RETURN_LOCK_TASK_MODE_VIOLATION;
}
newTask = true;
targetStack = adjustStackFocus(r, newTask);
if (!launchTaskBehind) {
targetStack.moveToFront();
}
if (reuseTask == null) {
r.setTask(targetStack.createTaskRecord(getNextTaskId(),
newTaskInfo != null ? newTaskInfo : r.info,
newTaskIntent != null ? newTaskIntent : intent,
voiceSession, voiceInteractor, !launchTaskBehind /* toTop */),
taskToAffiliate);
if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r + " in new task " +
r.task);
} else {
r.setTask(reuseTask, taskToAffiliate);
}
if (!movedHome) {
if ((launchFlags &
(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_TASK_ON_HOME))
== (Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_TASK_ON_HOME)) {
// Caller wants to appear on home activity, so before starting
// their own activity we will bring home to the front.
r.task.setTaskToReturnTo(HOME_ACTIVITY_TYPE);
}
}
} else if (sourceRecord != null) {
final TaskRecord sourceTask = sourceRecord.task;
if (isLockTaskModeViolation(sourceTask)) {
Slog.e(TAG, "Attempted Lock Task Mode violation r=" + r);
return ActivityManager.START_RETURN_LOCK_TASK_MODE_VIOLATION;
}
targetStack = sourceTask.stack;
targetStack.moveToFront();
final TaskRecord topTask = targetStack.topTask();
if (topTask != sourceTask) {
targetStack.moveTaskToFrontLocked(sourceTask, r, options);
} else {
mWindowManager.moveTaskToTop(topTask.taskId);
}
if (!addingToTask && (launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0) {
// In this case, we are adding the activity to an existing
// task, but the caller has asked to clear that task if the
// activity is already running.
ActivityRecord top = sourceTask.performClearTaskLocked(r, launchFlags);
keepCurTransition = true;
if (top != null) {
ActivityStack.logStartActivity(EventLogTags.AM_NEW_INTENT, r, top.task);
top.deliverNewIntentLocked(callingUid, r.intent);
// For paranoia, make sure we have correctly
// resumed the top activity.
targetStack.mLastPausedActivity = null;
if (doResume) {
targetStack.resumeTopActivityLocked(null);
}
ActivityOptions.abort(options);
return ActivityManager.START_DELIVERED_TO_TOP;
}
} else if (!addingToTask &&
(launchFlags&Intent.FLAG_ACTIVITY_REORDER_TO_FRONT) != 0) {
// In this case, we are launching an activity in our own task
// that may already be running somewhere in the history, and
// we want to shuffle it to the front of the stack if so.
final ActivityRecord top = sourceTask.findActivityInHistoryLocked(r);
if (top != null) {
final TaskRecord task = top.task;
task.moveActivityToFrontLocked(top);
ActivityStack.logStartActivity(EventLogTags.AM_NEW_INTENT, r, task);
top.updateOptionsLocked(options);
top.deliverNewIntentLocked(callingUid, r.intent);
targetStack.mLastPausedActivity = null;
if (doResume) {
targetStack.resumeTopActivityLocked(null);
}
return ActivityManager.START_DELIVERED_TO_TOP;
}
}
// An existing activity is starting this new activity, so we want
// to keep the new one in the same task as the one that is starting
// it.
r.setTask(sourceTask, null);
if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r
+ " in existing task " + r.task + " from source " + sourceRecord); } else if (inTask != null) {
// The calling is asking that the new activity be started in an explicit
// task it has provided to us.
//在调用者指定的确定的task中开启目标activity
if (isLockTaskModeViolation(inTask)) {
Slog.e(TAG, "Attempted Lock Task Mode violation r=" + r);
return ActivityManager.START_RETURN_LOCK_TASK_MODE_VIOLATION;
}
targetStack = inTask.stack;
targetStack.moveTaskToFrontLocked(inTask, r, options);
targetStack.moveToFront();
mWindowManager.moveTaskToTop(inTask.taskId); // Check whether we should actually launch the new activity in to the task,
// or just reuse the current activity on top.
ActivityRecord top = inTask.getTopActivity();
if (top != null && top.realActivity.equals(r.realActivity) && top.userId == r.userId) {
if ((launchFlags & Intent.FLAG_ACTIVITY_SINGLE_TOP) != 0
|| launchSingleTop || launchSingleTask) {
ActivityStack.logStartActivity(EventLogTags.AM_NEW_INTENT, top, top.task);
if ((startFlags&ActivityManager.START_FLAG_ONLY_IF_NEEDED) != 0) {
// We don't need to start a new activity, and
// the client said not to do anything if that
// is the case, so this is it!
return ActivityManager.START_RETURN_INTENT_TO_CALLER;
}
top.deliverNewIntentLocked(callingUid, r.intent);
return ActivityManager.START_DELIVERED_TO_TOP;
}
} if (!addingToTask) {
// We don't actually want to have this activity added to the task, so just
// stop here but still tell the caller that we consumed the intent.
ActivityOptions.abort(options);
return ActivityManager.START_TASK_TO_FRONT;
} r.setTask(inTask, null);
if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r
+ " in explicit task " + r.task); } else {
// This not being started from an existing activity, and not part
// of a new task... just put it in the top task, though these days
// this case should never happen.
targetStack = adjustStackFocus(r, newTask);
targetStack.moveToFront();
ActivityRecord prev = targetStack.topActivity();
r.setTask(prev != null ? prev.task : targetStack.createTaskRecord(getNextTaskId(),
r.info, intent, null, null, true), null);
mWindowManager.moveTaskToTop(r.task.taskId);
if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r
+ " in new guessed " + r.task);
} mService.grantUriPermissionFromIntentLocked(callingUid, r.packageName,
intent, r.getUriPermissionsLocked(), r.userId); if (sourceRecord != null && sourceRecord.isRecentsActivity()) {
r.task.setTaskToReturnTo(RECENTS_ACTIVITY_TYPE);
}
if (newTask) {
EventLog.writeEvent(EventLogTags.AM_CREATE_TASK, r.userId, r.task.taskId);
}
ActivityStack.logStartActivity(EventLogTags.AM_CREATE_ACTIVITY, r, r.task);
targetStack.mLastPausedActivity = null;
//继续调用目标ActivityStack的startActivityLocked()方法，这个方法没有返回值，执行完毕之后直接返回START_SUCCESS
targetStack.startActivityLocked(r, newTask, doResume, keepCurTransition, options);
if (!launchTaskBehind) {
// Don't set focus on an activity that's going to the back.
mService.setFocusedActivityLocked(r);
}
return ActivityManager.START_SUCCESS;
}
实际场景分析
实际场景1:
应用内有两个Activity,A和B,A为第应用入口Activity，从A可跳转至B，A和B的启动模式都为standard
1)从Launcher程序第1次启动应用时的任务调度情况:
任务调度时会创建新task并将新的ActivityRecord加入这个新的task
2)然后跳转至应用内Activity时的任务调度情况:
任务调度时会将新的ActivityRecord加入已有的task
3)然后按Home键，再打开应用程序时的调度情况:
任务调度时会先找到已有的相关task，并显示栈顶的Activity
1)从Launcher程序第1次启动应用时
会创建新task并将新的ActivityRecord加入这个新的task，任务调度执行如下所示:
final int startActivityUncheckedLocked(ActivityRecord r,
ActivityRecord sourceRecord, int startFlags, boolean doResume,
Bundle options) {
//...
//launchFlags为FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
int launchFlags = intent.getFlags();
//...
//没设置FLAG_ACTIVITY_PREVIOUS_IS_TOP，故此notTop为null
ActivityRecord notTop = (launchFlags&Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP)
!= 0 ? r : null;
//startFlags未设置ActivityManager.START_FLAG_ONLY_IF_NEEDED
//...
//sourceRecord为Launcher应用的Activity launcher应用activity的启动模式为singleTask
// 故此下面的3个条件分支的内容都不会执行
if (sourceRecord == null) {
//...
} else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//...
} else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
//...
}
//...
//r.resultTo不为null， launchFlags设置了FLAG_ACTIVITY_NEW_TASK，需要将r.resultTo置为null
if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
//...
r.resultTo = null;
}
boolean addingToTask = false;
boolean movedHome = false;
TaskRecord reuseTask = null;
//因为launchFlags为FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
//故此下面的条件会满足， 也就是说只要从Launcher程序启动应用，下面这个条件肯定会满足
if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
(launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//...
if (r.resultTo == null) {
//因为应用被第一次启动，故此找不到相关task，taskTop则为null
ActivityRecord taskTop = r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE
? findTaskLocked(intent, r.info)
: findActivityLocked(intent, r.info);
if (taskTop != null) {
//... 这里面的内容不会执行
}
}
}
//...
//r.packageName != null
if (r.packageName != null) {
//如果被启动的Activity正好是栈顶的Activity，
//并且被启动的Activity启动模式是singleTop或者singleTask，
//则不用将新的ActivityRecord加入到栈里
//top Activity为Launcher应用的Activity
ActivityRecord top = topRunningNonDelayedActivityLocked(notTop);
if (top != null && r.resultTo == null) {
//top.realActivity.equals(r.realActivity)不满足
if (top.realActivity.equals(r.realActivity) && top.userId == r.userId) {
//... 这里的代码不会被执行
}
}
} else {
//...
}
boolean newTask = false;
boolean keepCurTransition = false;
// 此时 r.resultTo为null addingToTask为false launchFlags设置了FLAG_ACTIVITY_NEW_TASK
if (r.resultTo == null && !addingToTask
&& (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
if (reuseTask == null) {
// todo: should do better management of integers.
mService.mCurTask++;
if (mService.mCurTask <= 0) {
mService.mCurTask = 1;
}
//创建新task
r.setTask(new TaskRecord(mService.mCurTask, r.info, intent), null, true);
if (DEBUG_TASKS) Slog.v(TAG, "Starting new activity " + r
+ " in new task " + r.task);
} else {
//...这里的代码会执行
}
newTask = true;
if (!movedHome) {
moveHomeToFrontFromLaunchLocked(launchFlags);
}
} else if (sourceRecord != null) {
//... 这里的代码不会被执行
} else {
//...这里的代码不会被执行
}
//...
startActivityLocked(r, newTask, doResume, keepCurTransition, options);
return ActivityManager.START_SUCCESS;
}
2)跳转至应用内Activity时
会将新的ActivityRecord加入已有的task，任务调度执行如下所示:
final int startActivityUncheckedLocked(ActivityRecord r,
ActivityRecord sourceRecord, int startFlags, boolean doResume,
Bundle options) {
//此时launchFlags为0
int launchFlags = intent.getFlags();
//notTop为null
ActivityRecord notTop = (launchFlags&Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP)
!= 0 ? r : null;
//startFlags未设置ActivityManager.START_FLAG_ONLY_IF_NEEDED
//...
if (sourceRecord == null) {
//...这里的代码不会被执行
} else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//...这里的代码不会被执行
} else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
//...这里的代码不会被执行
}
//r.resultTo != null 但是launchFlags未设置FLAG_ACTIVITY_NEW_TASK
if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
//... 这里的代码不执行
}
boolean addingToTask = false;
boolean movedHome = false;
TaskRecord reuseTask = null;
//launchFlags为0 r的启动模式为standard 故此下面的逻辑都不会执行
if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
(launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//... 这里的代码不执行
}
//...
if (r.packageName != null) {
//top 是ActivityA 的ActivityRecord，
//但是被启动的Activity和top不是同一个Activity
ActivityRecord top = topRunningNonDelayedActivityLocked(notTop);
if (top != null && r.resultTo == null) {
if (top.realActivity.equals(r.realActivity) && top.userId == r.userId) {
//...这里的代码不执行
}
}
} else {
//...这里的代码不执行
}
boolean newTask = false;
boolean keepCurTransition = false;
//此时 r.resultTo !=null sourceRecord != null addingToTask=false
if (r.resultTo == null && !addingToTask
&& (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
//...这里的代码不执行
} else if (sourceRecord != null) {
if (!addingToTask &&
(launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0) {
//... 这里的代码不执行
} else if (!addingToTask &&
(launchFlags&Intent.FLAG_ACTIVITY_REORDER_TO_FRONT) != 0) {
//... 这里的代码不执行
}
//添加到现有的task
r.setTask(sourceRecord.task, sourceRecord.thumbHolder, false);
//...
} else {
//... 这里的代码不执行
}
//...
return ActivityManager.START_SUCCESS;
}
3)然后按Home键，再打开应用程序
此时会先找到已有的相关task，并显示栈顶的Activity，任务调度执行如下所示:
final int startActivityUncheckedLocked(ActivityRecord r,
ActivityRecord sourceRecord, int startFlags, boolean doResume,
Bundle options) {
//...
//launchFlags为FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
int launchFlags = intent.getFlags();
//notTop为null
ActivityRecord notTop = (launchFlags&Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP)
!= 0 ? r : null;
//startFlags未设置ActivityManager.START_FLAG_ONLY_IF_NEEDED
//...
if (sourceRecord == null) {
//...这里的代码不会被执行
} else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//...这里的代码不会被执行
} else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
//...这里的代码不会被执行
}
//此时 r.resultTo != null launchFlags设置了FLAG_ACTIVITY_NEW_TASK
if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
//...
r.resultTo = null;
}
boolean addingToTask = false;
boolean movedHome = false;
TaskRecord reuseTask = null;
//此时launchFlags设置了FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
(launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//此时 r.resultTo == null
if (r.resultTo == null) {
//此时已有相关task，并且task 栈的栈顶是Activity B的ActivityRecord
//故此taskTop为Activity B的ActivityRecord
ActivityRecord taskTop = r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE
? findTaskLocked(intent, r.info)
: findActivityLocked(intent, r.info);
if (taskTop != null) {
//...
// 此时curTop是Launcher应用的Activity的ActivityRecord
ActivityRecord curTop = topRunningNonDelayedActivityLocked(notTop);
if (curTop != null && curTop.task != taskTop.task) {
r.intent.addFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
//此时Launcher应用的task在栈顶，故此callerAtFront为true，
//此时会把被启动的应用的task移至栈顶
boolean callerAtFront = sourceRecord == null
|| curTop.task == sourceRecord.task;
if (callerAtFront) {
// We really do want to push this one into the
// user's face, right now.
movedHome = true;
moveHomeToFrontFromLaunchLocked(launchFlags);
moveTaskToFrontLocked(taskTop.task, r, options);
options = null;
}
}
//此时launchFlags设置了FLAG_ACTIVITY_NEW_TASK|FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
//此时需要重置task 重置完后 taskTop为ActivityB的ActivityRecord
if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {
taskTop = resetTaskIfNeededLocked(taskTop, r);
}
//startFlags为0
if ((startFlags&ActivityManager.START_FLAG_ONLY_IF_NEEDED) != 0) {
//... 这些代码都不会被执行
}
//根据launchFlags和被启动的activity的信息 设置resueTask addingTask变量的值
//没设置 Intent.FLAG_ACTIVITY_CLEAR_TASK
if ((launchFlags &
(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK))
== (Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK)) {
//... 这些代码都不会被执行
} else if ((launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//... 这些代码都不会被执行
} else if (r.realActivity.equals(taskTop.task.realActivity)) {
//... 这些代码都不会被执行
} else if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) == 0) {
//因为从Launcher程序启动时launchFlags设置了FLAG_ACTIVITY_RESET_TASK_IF_NEEDED
//所以不会进入该分支
//... 这些代码都不会被执行
} else if (!taskTop.task.rootWasReset) {
//... 这些代码都不会被执行
}
//此时addingToTask为false，reuseTask为null，故此显示栈顶Actvity即可
if (!addingToTask && reuseTask == null) {
// We didn't do anything... but it was needed (a.k.a., client
// don't use that intent!) And for paranoia, make
// sure we have correctly resumed the top activity.
if (doResume) {
resumeTopActivityLocked(null, options);
} else {
ActivityOptions.abort(options);
}
return ActivityManager.START_TASK_TO_FRONT;
}
}
}
}
//... 以下代码都不会被执行
}
实际场景2:
应用内有两个Activity,A和B,A为第应用入口Activity，从A可跳转至B，A的启动模式都为standard，B的启动模式为singleTop
此时已从Launchenr程序打开应用，启动了Actvity A,再从A跳转至B，此时的任务调度情况:
此时不会创建新的Task，而是将B的ActivityRecord加入到A所在的task里
任务调度执行如下所示:
final int startActivityUncheckedLocked(ActivityRecord r,
ActivityRecord sourceRecord, int startFlags, boolean doResume,
Bundle options) {
//...
//此时launcheFlags为0
int launchFlags = intent.getFlags();
//notTop为null
ActivityRecord notTop = (launchFlags&Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP)
!= 0 ? r : null;
//默认情况下startFlags不会设置START_FLAG_ONLY_IF_NEEDED
if ((startFlags&ActivityManager.START_FLAG_ONLY_IF_NEEDED) != 0) {
//...这里的代码不会执行
}
//r.launchMode = ActivityInfo.LAUNCH_SINGLE_TASK
if (sourceRecord == null) {
//这里的代码不会执行
} else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//这里的代码不会执行
} else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
}
//此时r.resultTo!=null launchFlags设置了Intent.FLAG_ACTIVITY_NEW_TASK
if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
//...
r.resultTo = null;
}
//addingToTask如果为true表示正在添加至某个task，后续需要将r添加至sourceRecord所在的task
boolean addingToTask = false;
//movedHome表示是否移动home task
boolean movedHome = false;
TaskRecord reuseTask = null;
if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
(launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
//此时 r.resultTo = null
if (r.resultTo == null) {
//此时找到的taskTop是Activity A的ActivityRecord，
//因为Actvity B和A的ActivityRecord所在的Task是相关的
ActivityRecord taskTop = r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE
? findTaskLocked(intent, r.info)
: findActivityLocked(intent, r.info);
//找到了相关task
if (taskTop != null) {
//重设task的intent
if (taskTop.task.intent == null) {
//...
}
//此时找到的task已在栈顶
ActivityRecord curTop = topRunningNonDelayedActivityLocked(notTop);
if (curTop != null && curTop.task != taskTop.task) {
//... 这里的代码不会执行
}
//launchFlags为0
if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {
taskTop = resetTaskIfNeededLocked(taskTop, r);
}
//... 一般情况下startFlags 不会设置 START_FLAG_ONLY_IF_NEEDED
if ((startFlags&ActivityManager.START_FLAG_ONLY_IF_NEEDED) != 0) {
//...
}
// ==================== begin
// launchFlags此时为0
if ((launchFlags &
(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK))
== (Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_CLEAR_TASK)) {
//...这里的代码不执行
} else if ((launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
// r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
// 故此会进入该分支
//因为B还从未启动，故此得到的top为null
ActivityRecord top = performClearTaskLocked(
taskTop.task.taskId, r, launchFlags);
if (top != null) {
//...这里的代码不执行
} else {
addingToTask = true;
sourceRecord = taskTop;
}
} else if (r.realActivity.equals(taskTop.task.realActivity)) {
//...这里的代码不执行
} else if ((launchFlags&Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) == 0) {
//...这里的代码不执行
} else if (!taskTop.task.rootWasReset) {
//...这里的代码不执行
}
// ==================== end
// 此时 addingToTask为true
if (!addingToTask && reuseTask == null) {
//...这里的代码不执行
}
}
}
}
//...
if (r.packageName != null) {
ActivityRecord top = topRunningNonDelayedActivityLocked(notTop);
if (top != null && r.resultTo == null) {
//此时task还没有B的ActivityRecord，故此不会进入下述分支
if (top.realActivity.equals(r.realActivity) && top.userId == r.userId) {
//...这里的代码不执行
}
}
} else {
//...这里的代码不执行
}
boolean newTask = false;
boolean keepCurTransition = false;
// 此时 r.resultTo == null addingToTask为true sourceRecord != null
if (r.resultTo == null && !addingToTask
&& (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
//...这里的代码不执行
} else if (sourceRecord != null) {
if (!addingToTask &&
(launchFlags&Intent.FLAG_ACTIVITY_CLEAR_TOP) != 0) {
//...这里的代码不执行
} else if (!addingToTask &&
(launchFlags&Intent.FLAG_ACTIVITY_REORDER_TO_FRONT) != 0) {
//...这里的代码不执行
}
//将B的ActivityRecord加入A的ActivityRecord所在的Task里
r.setTask(sourceRecord.task, sourceRecord.thumbHolder, false);
//...
} else {
//...这里的代码不执行
}
//...
startActivityLocked(r, newTask, doResume, keepCurTransition, options);
return ActivityManager.START_SUCCESS;
}
总结
从上面的分析可以看出来，Activity和Task的调度算法非常复杂，需结合实际场景才好分析，只有这样才知道是否需要新建Task,还是将新的ActivityRecord加入到已有的Task里，不过我们如果能理解启动模式的一些特点，对理解调度算法会有很大帮助。
大家可以结合下述场景分析调度算法:
1.从通知栏启动Activity:
假设应用有Activity A ，Activity A已启动，
此时发了一个通知，该通知用于启动Activity A，启动Activity A时不加任何特殊flag
点击通知，针对以下情况对任务调度情况进行分析:
Activity A的启动模式为standard
Activity A的启动模式为singleTop
Activity A的启动模式为singleTask
Activity A的启动模式为singleInstance
2.跨应用跳转Activity
假设应用app1有一个Activity A，另一个应用app2有一个Activity B
Activity A可跳转至Activity B
因为Activity A和Actiivty B在不同应用，所以Activity的taskffinity必然不同
现在Activity A已启动，跳转至Activity B，
针对以下4种情况分析跳转之后的Activity Task情况
Activity B的启动模式为standard
Activity B的启动模式为singleTop
Activity B的启动模式为singleTask
Activity B的启动模式为singleInstance
如果大家对上述场景分析有兴趣的话，可以在评论里一起探讨结果。
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