Office Hours — Today, December 11

← Yesterday, December 10

Dec 11
9:50 AM
Mark M.
has entered the room
Mark M.
turned on guest access
9:55 AM
Guy W.
has entered the room
Mark M.
hello, Guy!
how can I help you today?
Guy W.
Hello
struggling with a custom spinner adapter
customising the Drop Down
Oleg T.
has entered the room
10:00 AM
Mark M.
(BTW, hello, Oleg -- I will be with you shortly!)
Guy: could you be more specific?
Oleg T.
Good day
Guy W.
I think it works now :-)
Mark M.
um, OK, let me take a question from Oleg, and I'll be back with you in a bit
Oleg: do you have a question?
Oleg T.
Cheers. I do have a somewhat weird one
When we store instancestate in a Bundle. Where does the data actually live and for how long?
Mark M.
the instance state is sent back to a core OS process, one that manages the tasks and back stack for each
it will "live" as long as that instance state is still reachable, such as via the recent-tasks list
your process, of course, may go away, which is why the state is held in a central OS process
Oleg T.
Does it ever happen so that the data will be wiped out before we get back to it? say, something odd happens while the phone is being rotated?
Mark M.
I don't know how to answer that
Oleg T.
no worries. it must be a silly one since I'm an amateur
Mark M.
I have never seen the saved instance state Bundle be lost during a configuration change, if that's what you mean
10:05 AM
Oleg T.
ok. i guess i'll pass the mic
Mark M.
Guy: do you have another question?
Guy W.
yes. thanks
I have an intent that goes to Intent i = new Intent(Settings.ACTION_WIRELESS_SETTINGS);
Alex F.
has entered the room
Mark M.
(BTW, hello, Alex, I will be with you shortly!)
Guy W.
after pressing back where do I need to refresh the view? app lifecycle
Mark M.
onResume() is a typical spot, as that is called after both onCreate() and when you are about to return to the foreground from an input standpoint
10:10 AM
Mark M.
I assume that you are looking to refresh based upon changes the user made in Settings?
Guy W.
yes
Mark M.
I would start with onResume(), moving it elsewhere (e.g., onStart()) if needed
let me take questions from the others, and I will be back with you in a bit
Alex: do you have a question?
Alex F.
Yes.
When adding Fragments to a FrameLayout, the newest Fragment is stacked on top of the oldest. Is this stacking behavior dictated by the FrameLayout? My goal is to change this behavior so that Fragments are added behind the oldest Fragment.
Guy W.
I tried onResume with a toast, and noticed it refreshed twice without going to the settings.
Mark M.
yes, FrameLayout (and RelativeLayout) treat later children as being higher on the Z axis, therefore floating over earlier children
(Guy: I will be back with you in a bit)
Guy W.
thanks
Mark M.
Alex: off the cuff, I do not know how you would go about running a FragmentTransaction that would add a fragment under an existing one
what is your use case for having two fragments visible in the same container at the same time, anyway?
10:15 AM
Mark M.
OK, let me take questions from others, and I will be back with you in a bit
Oleg: do you have another question?
Oleg T.
i do
let me know is it's more than one and i'll wait. there you go:
View paste 
Are there any standards on which implicit intents the standard apps must support?
For example, Contacts app has quite a few layouts but I'm not sure if there is a way
to craft an Intent for each one of those. What's the general approach (how do I know if I must pass data, extas, categories, etc)?
Mark M.
"Are there any standards on which implicit intents the standard apps must support?" -- whatever is documented in the Android SDK
unfortunately, Intent structures tend to be documented all over the place
Oleg T.
so it is a bit of a problem since different vendors ship different apps
Mark M.
ah
the Compatibility Definition Document will help there
http://source.android.com/compatibility/index.html
it lists the core apps whose implicit Intents are considered to be mandatory to be supported by the device when it ships
Oleg T.
i'll have a go at it, thanks
Alex F.
Mark, the idea is to show a fragment (most likely nesting a ViewPager inside this fragment) and after a specific action (swiping past an x number of pages), load a new fragment behind the current and when reached at the end of the ViewPager, detach the top fragment and revealing the added fragment.
Mark M.
Oleg: that being said, devices sans legal copies of the Play Store will not necessarily honor the CDD, users might install third-party replacement apps, and the Compatibility Test Suite does not necessarily catch all device manufacturer bugs in this area
(Alex: I will be back with you shortly)
10:20 AM
Oleg T.
understood, Mark
Mark M.
Guy: onResume() is called after onCreate(), on configuration changes, and when your activity is returning to the screen after having been in the background
your job in onResume(), as with all callback methods like the lifecycle methods, is to be quick and cheap
Guy W.
thanks. I'll try it again later
Mark M.
Alex: why not replace() the ViewPager with the alternative fragment "when reached at the end"?
IOW, why does it have to be there in advance? and why does it have to be there *after* the ViewPager was added?
Alex F.
To animate the top fragment out of view, revealing the added fragment
Mark M.
then put the to-be-revealed fragment in place before adding the ViewPager fragment
why do you have to delay adding it until "after a specific action"?
or, why can't you have a container for the to-be-revealed fragment put in place ahead of time?
10:25 AM
Mark M.
FrameLayout holding onto another FrameLayout and the ViewPager
put the to-be-revealed fragment in the nested FrameLayout
that way, you can add the to-be-revealed fragment when you need to, but from a Z-axis standpoint, it is under the ViewPager, because its FrameLayout is under the ViewPager
Guy W.
has left the room
Guy W.
has entered the room
Alex F.
that would work if the new fragment is known ahead of time. or at least the data that the new fragment will contain. lets say there's a stack of fragments that represents pages in a book and the contents of each page is fetched from some server. i can load up the first 10 pages but lets say after swiping away 8 pages, i'd like to load more pages behind the current one.
Mark M.
IMHO, that would be adding pages to the ViewPager, not swapping in some other fragment
let me take questions from the others, and I will be back with you in a bit
Oleg: do you have another question?
Oleg T.
yes
View paste 
related to the previous one. i've looked in the doco: For every Activity or Service defined in one of the core Android system apps that is not marked as non-public via an
android:exported attribute with the value "false", device implementations MUST include a component of the same type
implementing the same Intent filter patterns as the core Android system app.
where would I start digging in terms of documentation?
Mark M.
in terms of what is and is not exported, look at the manifest of the app in question (e.g., Contacts)
10:30 AM
Mark M.
in terms of filter patterns, same thing
in terms of eligible extras, these should all be in the Android SDK somewhere, documented wherever the Intent action string is
Oleg T.
are those documented?
Mark M.
what is "those"?
Oleg T.
manifest files for core apps
Mark M.
they are in the AOSP source code
Oleg T.
ok
Mark M.
https://github.com/android/platform_packages_ap...
that's the one for Contacts, for example, from the GitHub mirror of the AOSP
these change over time, with different Android versions, which makes this a bit tedious to document
Oleg T.
thanks. that would be all from me for the night(day). cheers
Mark M.
OK
Guy: do you have another question?
Oleg T.
has left the room
10:35 AM
Mark M.
OK, if either of you have a question, go ahead
10:40 AM
Guy W.
has left the room
10:45 AM
Mark M.
Alex: if you have another question, go ahead
11:00 AM
Mark M.
that's a wrap for today's chat
View paste 
the transcript will be archived on http://commonsware.com/office-hours/ shortly
the next chat is tomorrow at 4pm Eastern
have a pleasant day!
Alex F.
has left the room
Mark M.
turned off guest access

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Office Hours

People in this transcript

  • Alex Fu
  • Guy West
  • Mark Murphy
  • Oleg Tikhonov