Is there an easy way to view a list of recent activities? The one I'm looking for doesn't seem to be showing up in the main recent apps view, and
adb logcat is so noisy I'm having a hard time finding anything.
For Lollipop do
adb shell dumpsys activity recents. For some earlier Android version, run
adb shell dumpsys activity activities.
Alternatively, you may run
adb shell dumpsys activity | grep -i run as noted by loeschg here.
You would get a list of recent apps' package name, component (activity) name, flags among other things.
In Lollipop, if you've root access, you can browse to
/data/system/recent_tasks/. You'll find some XML files with numeral names, such as
317.xml. Each of them consists of the same aforesaid details, but each XML file is created for an individual app.
You can also get some info from
adb shell dumpsys usagestats.
Answering my own question...
I had pretty decent results using Event Logger to show App Started events. This revealed that the mystery activity was the system upgrade activity popping up and immediately dismissing itself.