Develop Reference

Is it possible to know the app which is opened currently?

I am a beginner in android development. I want to know that is it possible to know the app which is opened currently. I came to know that finding the apps which are running currently through Activity Manager (getRunningTasks()) is now removed from the Android studio. So I want to know is there any other way to know? I just want to know the app which is opened and running currently on the mobile but not the apps running in the background Could somebody please help me in this case?

You can use AccessibilityService to get event notification. But AccessibilityService are specifically for accessibility uses. If you use the service for other purposes, then the application will more likely to be downed/removed for PlayStore due to policies. Another viable option is UsageStatsManager, but with some limitations.
UsageStatsManager is not push event based system. You have to poll in few mills(depends upon the use-case)
Usage Access Permission grant/deny is not straight forward. You have to start Setting Activity with Settings#ACTION_USAGE_ACCESS_SETTINGS action and have to rely on the users understanding of how to grant permission(Since permission list may contain other applications).

Remove android setting screen from recent list [duplicate]

I was wondering if anyone had a relatively simple solution for us.
We created an app to be used by our clients on android devices that we give them.
We would like the client to only be able to use our app and have limited access to everything else (i.e. settings, email etc.) What is the best way to achieve this without using 3rd party apps.
Thank you in advance!

This may not help but the L preview has a task locking feature included that may be of some insight, I'm not aware of how it functions as yet
Task locking
The L Developer Preview introduces a new task locking API that lets you temporarily restrict users from leaving your app or being interrupted by notifications. This could be used, for example, if you are developing an education app to support high stakes assessment requirements on Android. Once your app activates this mode, users will not be able to see notifications, access other apps, or return to the Home screen, until your app exits the mode.
http://developer.android.com/preview/api-overview.html
Hope this helped

Suppress the Title Bar & Make Your App a Launcher
Root Your Tablet
Modify System Files and Settings to hide the soft keys
On the next link you can find the complete solution for the Nexus 7 (2012)
http://thebitplague.wordpress.com/2013/04/05/kiosk-mode-on-the-nexus-7/

simple Answer is:
Lock Install button with modify system settings.
Create your own customized-ROM and apply your requirement to that ROM.
more info, visit XDADavelopers

How to update Android OS on the device through an App

Is there any way to update the Android OS through an App(Using Android API or any other API/) after checking if a newer Android version is available in the market/Playstore
The Use Case required to be supported here is as follows:
The App starts and checks the version of the installed Android OS
It then finds the version of available Android OS in the
Playstore/other repository for that device
Then it compares the two version and if the available version is
newer, then it installs the new Android version on the device
How can it be implemented , especially the third point ? I do not want to root the device for that, so if there is any way to achieve this, please help ....

There is no API. If your device has an update feature built in (most do), you can decompile the update service and see how it works. If your device does not have an update feature, then you can look at custom ROMs for your device. Once you get ahold of a ROM or an update.zip you want to use, the process cannot be done automatically. The updating takes place in the system recovery mode where the user will have to select the .zip to update. However, if you can decompile and figure out how your manufacturer's update service works, maybe you can pull off an automated process.
There aren't any tutorials or documentation for this, as it is 100% dependent on phone model/OS. You can probably find a flashable ROM for your device, however, but the process is rarely automated. Actually, take a look at ROM Manager in this case, it is a somewhat automated upgrade app. I tried it before and it bricked my phone. Good luck

You would need to know where to ask if there is a newer version. And then is there an upgrade available for that particular device. At that point you could broadcast a request to update. Does not the device know when an update is available?

For updating your android version you would need
Custom Android on you device.(Some more info)
Rooted device.why need rooting?
Now for installing we would need to flash ROM.You would also need to have check for version of the OS available, which depend upon your logic .Generally Samsung ,Sony they use custom android and the updates are pushed over app center( or something like that,not much knowledge) in your case it may be any cloud service or server to check version for your custom android.
When we have a new version, after user accepts to upgrade, a new img file would be downloaded to your device which would be used to upgrade the OS.Please note you would also need a recovery backup method too.There are some Commands that can be used to extract and download the OS through your code.
I haven't implemented it yet but this is the procedure i could find.
I hope this would help others.
UPDATE
I have got some new information about how can we initiate the update through code. the Link and there's this another link that can be great help.
In both the examples they are using SystemRcovery class with intallerPackage API.

How to make an app unclosable?

After a user opens my application I don't want them to be able to get out. So when they press the home or back button it doesn't let them exit the app. I know there are ways using a service to keep the app always running in the background, but I don't even want them to even exit.
Is this even possible, if so how? Without having to hack the kernel.
I know this sounds odd, but it is not for a commercial app, but for my lab, it will never be on GooglePlay. The tablets will be given to little kids and they will take a test on it, so I can't have them using youtube or anything else.
Related post: Android, How to make the task of the app unclosable? Only closable by task killing
The answer by CommonWare seems to indicate that kernel hacking is the only way, but is it?
Also I am using Android L.

there is no official support yet - there will be support with android L via the Task locking API
The L Developer Preview introduces a new task locking API that lets
you temporarily restrict users from leaving your app or being
interrupted by notifications. This could be used, for example, if you
are developing an education app to support high stakes assessment
requirements on Android. Once your app activates this mode, users will
not be able to see notifications, access other apps, or return to the
Home screen, until your app exits the mode.
https://developer.android.com/preview/api-overview.html
EDIT: as you said you use L this got obsolete - but I leave it here as a hint for others
said that - you are also able to get this kind of work without root today if you have to ( e.g. kiosk mode app on a certain hardware ). It is not simple - and no solution that works for all devices - but if you need it you can get it work with tricks like:
- reacting on home-screen intent ( and setting it as default )
- when you go to background - bring your self foreground again
- ..

It seems google has some thing called COSU for setting up single-purpose devices
Android 5.0 Lollipop introduced two new ways to configure Android
devices for a single purpose:
With app pinning, the device user can temporarily pin specific apps to the screen.
With lock task mode, a user can’t escape the app and the Home and Recents buttons are hidden. Additionally, lock task mode gives the IT
administrator a more robust way to manage COSU devices, as discussed
below.
and
As an IT administrator, you can configure Android 6.0 Marshmallow and
later devices as corporate-owned, single-use (COSU) devices. These are
Android devices used for a single purpose, such as digital signage,
ticket printing, point of sale, or inventory management. To use
Android devices as COSU devices, you need to develop Android apps that
your customers can manage.
from here
and there is a code lab for it here
for earlier versions of android here i founded How-To Create a Working Kiosk Mode in Android which shows some hacks for disabling buttons and restarting the application after boot and lock. note that most of these hacks, don't work on android 6 and later

"One App" Android System

I created an Android app which communicates via USART with a µC in order to evaluate data. My co-workers and customers should use the tablet for only this purpose now. Is there any possibility to "hide" the Android OS or making it inaccessible?
Devices are rooted and I am willing to build custom ROMs (even though I do not have any experience with that yet). Are there any approaches available that I do not have to start from scratch?
Many thanks for your help.

Well. That what I'm trying to do !
The first thing I tried was to start the app just after the boot of the device (Quite easy with this).
Then, I get Android source code, and I hide the bottom bar using this code
The problem is, if your application is not stable ... you'll have some problem.
If you want to modify Android source code, the developper doc contains a very good tutorial to start !