What "Stack" means in 'adb shell dumpsys activity'?

Question

Running adb shell dumpsys activity activities shows the current tasks and its activities. But the tasks are grouped by "Stacks" (eg. Stack #0, Stack #1). What those Stacks means?

The following result below shows an example. I've opened Play Store (Task id #694) then browsed to an app in it and touched in the developer's e-mail, which open a new task for G-Mail (Task id #696). After that I touched in Home Button and opened G-Mail through home launcher (Task id #698)

If those tasks aren't related, then why they are in the same Stack and the Home Launcher app (Task id #693) and Recents Apps screen (Task id #697) are in different Stacks? Can someone explain what difference makes being in the same or in a different Stack?

Stack #1:
    Task id #698
    TaskRecord{9cfcd22 #698 A=com.google.android.gm U=0 StackId=1 sz=2}
        Hist #1: ActivityRecord{a926067 u0 com.google.android.gm/.welcome.SetupAddressesActivity t698}
        Hist #0: ActivityRecord{49b6dc1 u0 com.google.android.gm/.welcome.WelcomeTourActivity t698}
    Task id #696
    TaskRecord{e5e8110 #696 A=com.google.android.gm U=0 StackId=1 sz=1}
        Hist #0: ActivityRecord{2ee23f u0 com.google.android.gm/.ComposeActivityGmailExternal t696}
    Task id #694
    TaskRecord{f165f44 #694 A=com.android.vending U=0 StackId=1 sz=1}
        Hist #0: ActivityRecord{5b6ebee u0 com.android.vending/.AssetBrowserActivity t694}5,1668] }

Stack #0:
    Task id #693
    TaskRecord{e0f894 #693 I=com.motorola.launcher3/com.android.launcher3.CustomizationPanelLauncher U=0 StackId=0 sz=1}
        Hist #0: ActivityRecord{5e7d381 u0 com.motorola.launcher3/com.android.launcher3.CustomizationPanelLauncher t693}

Stack #5:
    Task id #697
    TaskRecord{a9c0639 #697 A=com.android.systemui U=0 StackId=5 sz=1}
        Hist #0: ActivityRecord{e45982b u0 com.android.systemui/.recents.RecentsActivity t697}

ResumedActivity: ActivityRecord{a926067 u0 com.google.android.gm/.welcome.SetupAddressesActivity t698}
mFocusedStack=ActivityStack{25782d stackId=1, 3 tasks} mLastFocusedStack=ActivityStack{25782d stackId=1, 3 tasks}

What "Stack" means in 'adb shell dumpsys activity'?

0 Answers0