本文主要分析
从当前activity打开另一个activity(此时第一个activity设置了new_task的标记)，这种情况比较简单,
从结果我们知道，这里startActivity无论如果设置了new_task的话就不会打开新的activity栈,(这里context无论是application级别的还是activity级别的都不会产生影响)
我们从ams代码里分析下
上面的就不多说了，这里还是找reusedActivity是否等于null的判断
void findTaskLocked(ActivityRecord target, FindTaskResult result) {
Intent intent = target.intent;
ActivityInfo info = target.info;
ComponentName cls = intent.getComponent();
if (info.targetActivity != null) {
cls = new ComponentName(info.packageName, info.targetActivity);
}
final int userId = UserHandle.getUserId(info.applicationInfo.uid);
boolean isDocument = intent != null & intent.isDocument();
// If documentData is non-null then it must match the existing task data.
Uri documentData = isDocument ? intent.getData() : null;
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Looking for task of " + target + " in " + this);
for (int taskNdx = mTaskHistory.size() - 1; taskNdx >= 0; --taskNdx) {
final TaskRecord task = mTaskHistory.get(taskNdx);
if (task.voiceSession != null) {
// We never match voice sessions; those always run independently.
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Skipping " + task + ": voice session");
continue;
}
if (task.userId != userId) {
// Looking for a different task.
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Skipping " + task + ": different user");
continue;
}
// Overlays should not be considered as the task's logical top activity.
final ActivityRecord r = task.getTopActivity(false /* includeOverlays */);
if (r == null || r.finishing || r.mUserId != userId ||
r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Skipping " + task + ": mismatch root " + r);
continue;
}
if (!r.hasCompatibleActivityType(target)) {
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Skipping " + task + ": mismatch activity type");
continue;
}
final Intent taskIntent = task.intent;
final Intent affinityIntent = task.affinityIntent;
final boolean taskIsDocument;
final Uri taskDocumentData;
if (taskIntent != null && taskIntent.isDocument()) {
taskIsDocument = true;
taskDocumentData = taskIntent.getData();
} else if (affinityIntent != null && affinityIntent.isDocument()) {
taskIsDocument = true;
taskDocumentData = affinityIntent.getData();
} else {
taskIsDocument = false;
taskDocumentData = null;
}
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Comparing existing cls="
+ (task.realActivity != null ? task.realActivity.flattenToShortString() : "")
+ "/aff=" + r.getTaskRecord().rootAffinity + " to new cls="
+ intent.getComponent().flattenToShortString() + "/aff=" + info.taskAffinity);
// TODO Refactor to remove duplications. Check if logic can be simplified.
if (task.realActivity != null && task.realActivity.compareTo(cls) == 0
&& Objects.equals(documentData, taskDocumentData)) {
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Found matching class!");
//dump();
if (DEBUG_TASKS) Slog.d(TAG_TASKS,
"For Intent " + intent + " bringing to top: " + r.intent);
result.mRecord = r;
result.mIdealMatch = true;
break;
} else if (affinityIntent != null && affinityIntent.getComponent() != null &&
affinityIntent.getComponent().compareTo(cls) == 0 &&
Objects.equals(documentData, taskDocumentData)) {
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Found matching class!");
//dump();
if (DEBUG_TASKS) Slog.d(TAG_TASKS,
"For Intent " + intent + " bringing to top: " + r.intent);
result.mRecord = r;
result.mIdealMatch = true;
break;
} else if (!isDocument && !taskIsDocument
&& result.mRecord == null && task.rootAffinity != null) {
if (task.rootAffinity.equals(target.taskAffinity)) {
if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Found matching affinity candidate!");
// It is possible for multiple tasks to have the same root affinity especially
// if they are in separate stacks. We save off this candidate, but keep looking
// to see if there is a better candidate.
result.mRecord = r;
result.mIdealMatch = false;
}
} else if (DEBUG_TASKS) Slog.d(TAG_TASKS, "Not a match: " + task);
}
}
这个target就是要打开的activity,也就是testActivity
这里由于task.realActivity为MainActivity，其rootAffinity和现在的testActivity相同，但是componentName不同，所以拿到的也就是MainActivity，这里不同与第一篇的case,第一篇的case的topActivity是已经resume过的
简单来说如果设置了newTask的属性，并且历史的activityStack有相对应可以匹配的值（compentName或者是taskaffity相同）就会走这个复用的逻辑
或者是singInstance这个以后在分析
接下来调用setTargetStackAndMoveToFrontIfNeeded方法
private ActivityRecord setTargetStackAndMoveToFrontIfNeeded(ActivityRecord intentActivity) {
mTargetStack = intentActivity.getActivityStack();
mTargetStack.mLastPausedActivity = null;
// 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.
final boolean differentTopTask;
if (mPreferredDisplayId == mTargetStack.mDisplayId) {
final ActivityStack focusStack = mTargetStack.getDisplay().getFocusedStack();
final ActivityRecord curTop = (focusStack == null)
? null : focusStack.topRunningNonDelayedActivityLocked(mNotTop);
final TaskRecord topTask = curTop != null ? curTop.getTaskRecord() : null;
differentTopTask = topTask != intentActivity.getTaskRecord()
|| (focusStack != null && topTask != focusStack.topTask());
} else {
// The existing task should always be different from those in other displays.
differentTopTask = true;
}
这里判断是不是是不同的taskrecord，也就是是不是不同的activityStack
对比标准是intentActivity所在的stack和当前看到的stack做对比，很明显是相同的情况，所以所以就不会走下面条件， 接下来
看下
if (reusedActivity != null) {
setTaskFromIntentActivity(reusedActivity);
if (!mAddingToTask && mReuseTask == 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.
resumeTargetStackIfNeeded();
if (outActivity != null && outActivity.length > 0) {
setTaskFromIntentActivity方法，这里把
else if ((mLaunchFlags & 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.
mAddingToTask = true;
mSourceRecord = intentActivity;
} else if (!intentActivity.getTaskRecord().rootWasReset) {
intentActivity也就是reusedActivity赋值给了sourceActivity（这里如果是application的context是没有source的，因为它的token传过来为null，但是这里给赋值了reusedActivity作为sourceRecord），接下来就走第二篇的逻辑了，所以在当前app设置new_task没有指定taskAffinty的情况下，可以说是毫无作用
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