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Detect when an android app goes to the background

Posted: Mon Jul 10, 2017 12:16 pm
by Gurgen
Hi All,

For the application that I'm working on now, I need somehow to change the app image in background mode when displaying all of the open applications on a mobile device(to hide some sensitive data). I'm looking for a way to detect when an android app goes to the background and come back to foreground.

Before spending time to wrap that functionality with Java FFI capabilities I want to ask if somebody does this or know any way to do this without externals?

Many thanks,
Gurgen

Re: Detect when an android app goes to the background

Posted: Mon Jul 10, 2017 4:51 pm
by jacque
I can't tell you how many times I've needed to know that. No messages are sent when an app goes to the background on Android, there are no suspend messages (and no resume messages either.)

If you get something working I'd be grateful if you could share it.

Re: Detect when an android app goes to the background

Posted: Tue Jul 11, 2017 11:12 am
by Gurgen
Hi Jacque,

I will let you know about progress.

--
Gurgen

Re: Detect when an android app goes to the background

Posted: Tue Jul 11, 2017 3:02 pm
by bogs
Just curious and thinking out loud as it were, but is this something the focusedObject could be used to test for?

(psuedo code)

Code: Select all

on mouseUp // or android equivalent, I don't code mobile...
   if the focusedObject is not a card or control of this stack then // probably needs a repeat loop to test with...
      objectToReturn = empty 
  end if
  end mouseUp
In other words, if the object being focused on isn't part of your android program, doesn't that mean your program is in the background by default?

Course, this could be faulty logic, just woke up :)

Re: Detect when an android app goes to the background

Posted: Wed Jul 12, 2017 3:08 pm
by Gurgen
For iOS we have found the way how to check it.

mergNotify - part of mergExt

Code: Select all

on openStack
  mergNotify "UIApplicationWillResignActiveNotification"
  mergNotify "UIApplicationDidBecomeActiveNotification"
end openStack

on UIApplicationWillResignActiveNotification pUserInfo
  // Your code before the app goes to background
end UIApplicationWillResignActiveNotification

on UIApplicationDidBecomeActiveNotification pUserInfo
 // Your code after the app comes back to foreground
end UIApplicationDidBecomeActiveNotification
Hope this is helpful .

--
Gurgen

Re: Detect when an android app goes to the background

Posted: Wed Jul 12, 2017 7:20 pm
by jacque
Thanks, but for now I'm mostly developing for Android. I'm hoping Monte wraps all his many iOS externals so they are compatible with that OS.

Re: Detect when an android app goes to the background

Posted: Wed Jul 12, 2017 7:27 pm
by jacque
bogs wrote:Just curious and thinking out loud as it were, but is this something the focusedObject could be used to test for?

(psuedo code)

Code: Select all

on mouseUp // or android equivalent, I don't code mobile...
   if the focusedObject is not a card or control of this stack then // probably needs a repeat loop to test with...
      objectToReturn = empty 
  end if
  end mouseUp
In other words, if the object being focused on isn't part of your android program, doesn't that mean your program is in the background by default?

Course, this could be faulty logic, just woke up :)
Unfortunately no. When an Android app goes into the background it is inaccessible. The user doesn't see it and can't interact with it until they re-open the app. However it does stay in RAM for a varying amount of time until the OS needs the memory, when it is summarily deleted. There is no notification when that happens. If the app is still in RAM but "closed" there are no messages sent when the user re-opens it because technically it is still open; that is, it doesn't relaunch, it just re-appears.

We could really use "suspend" and "resume" messages so the app knows when to take any necessary actions whenever the app comes to the front. If the OS has deleted the app from RAM then you do get all the usual startup/open-whatever messages. The problem is, when it is idling in the background and the user re-opens it, none of those occur.

Re: Detect when an android app goes to the background

Posted: Wed Jul 12, 2017 8:04 pm
by bogs
Good to know Jacque, thank you for the explanation.