I would like to get a list of users connected to internet and set their status as online. I am using Firebase Presence for it but it only works when the user in the application. When the user closes or minimizes the app, the status is set to offline but I want to keep the status online as long as the user has an active internet connection.
Note: I am using Android 8.0 and I know about limited background services.
How can I achieve this? Thank you.
Android may kill an app's process when it's no longer being used. This is something you should expect to happen. When that happens, Firebase will obviously lose its connection, and the app will be considered offline.
The only way to extend the life of your process is to start a foreground service in your app that stays active indefinitely. Even then, Android may still kill your app to make room for apps that are visible on screen. There is no way to guarantee that your app's process will never get killed for something more important to the end user.
Please read this documentation thoroughly to understand how Android prioritizes apps. Also read the documentation for Service.startForeground().
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A client of mine is requesting for a very specific functionality, to keep the application always active, even after the user force kills it. He wants to ensure that the users have the application active at any time while using the device on which it is installed (the devices are managed in a constrained environment).
I've done some research on it, and already enabled background services for sending the user's location, but if they force kill the app then we are unable to send locations to the server. We've seen other apps do it, but wonder how they do it.
According to https://stackoverflow.com/a/34573169/640907 it should be possible in Android. We also found https://ssaurel.medium.com/how-to-auto-restart-an-android-application-after-a-crash-or-a-force-close-error-1a361677c0ce but I don't think this will work for our use-case, as the user can close the application without "force kill" aswell..
Anyone knows how to achieve this for a Flutter application?
About Android (6.0 to the last version)
I'm developing an app and we want that the user, once he accepts all the terms, don't be able to kill the process or force stop the app. Honestly, I'm completely lost right now, because on the last versions of android, and specially some brands like Xiaomi, we are having a lot of trouble with it, and we don't know how to act right now.
In the case that it could not be possible, could at least get an alert whenever the user is killing the app?
Thanks!!
It is not possible to prevent the user from killing an app. Android is a unique system where the app has no direct control over its lifecycle but the system has. The system can (and will, when required) kill the app or any of its processes at its own will. To make your app aware of these changes, the android framework provides for various callbacks such as onPause, onStop and onDestroy which are called in succession when the user kills the app.
Side Note : There is no guarantee that onDestroy() will be completely executed when the app is killed. Do not place essential code there.
Of course, you can block or try to prevent the user from closing your app by overriding the back, home and recent buttons but it is highly recommended not to do so. Even if you do so successfully, the user has other means to close your app such as rebooting their phone.
So what to do?
You are looking for a kiosk mode app. Kiosk mode is used for single purpose phones such as at a restaurant or for a cab driver. Kiosk mode apps lock down the user to only a specific app (or a specific set of apps).
For normal apps, it is not possible to prevent the user from force closing your app. You can only get alerts by checking for lifecycle changes as described above. Moreover, it is not at all recommended to change the natural behavior of the hardware buttons on android. The user can still find a way to close your app. If your app is doing something really essential which should proceed in the background, consider using a service for that instead. Also, the user can uninstall your app at anytime if they find your app being too intrusive and you won't be able to do anything in that scenario.
Tl;dr: Use kiosk mode to prevent the user from exiting the app. This will only allow the user to access your app(s) in their device.
Usually you cannot! Even if you try to disable some buttons, user can always stop app or restart device. In addition at times, the OS will stop the App. Your responsibility as a programmer is to program around this, and give the user the feel that it never stopped. If you are doing background monitoring, you will need to use service. Users will still be able to stop service. Having said that, you can set your app as a Device Administration app, see here, which may disallow stopping, but unless you are distributing internally to a company, noone will install.
I've seen some "app locking" solutions in the Google Play store and I was wondering how those apps work. I'd like to build something similar.
I realize that this might require some special permission or maybe request the app to be added as device administrator.
Is there some broadcast that is triggered just before an app is launched that I can intercept and do some action (e.g. launch an activity that will request the user to fill a password)? I've read some lengthy discussions how this is not a good idea and the only idea is to have a background service that will continuously poll the running processes and check for changes, but I think retrieving this list every second and checking it for chances is not good for the battery and I think other app locking apps out there must be using a different approch.
If possible, without the need for a rooted phone.
I have a Bike computer app that logs data while the user is riding. I have had a user report an issue I had not considered. He was out for a long ride (100+ miles) but while out and logging data the app got updated via Google plays auto-update. This unfortunately killed off the app mid recording and the user lost data till they spotted what had happened and restarted the app.
Ideally I would like to be able to programmatic stop the auto-update happening while the app is data logging. All my research indicates that this is not possible possible but I may of missed something so dose anyone know of a way of doing this?
Given no solution the best I can do is advice the users to enable the update only over wifi option in the Play app which in this instance would of helped. Unfortunately one of the key points about my app is that it will log indoor sessions using ANT+ sensors so I have a good number of people using it with wifi active.
Edit
I managed to do the experiment to see what happens myself last night. I had an app going in the background data logging then pushed a new version to Google Play. Unfortunatly it was not picked up totaly automaticaly when I had to leave 10 hours latter but I opened up the play store app and it found the update it did not start updating automaticaly but I forced it. The act of downloading and installing the new version killed off what was in progress. It was already dead before I used the notification to go to the new version.
As you say yourself, you can't do that what you are asking for. You could hack your way around it by changing the permissions each time you update. The users will then be prompted about it in the regular way.
I'm not sure about the "life-cycle" for automatic updated apps that are running. But I read somewhere that is wasn't the re-install but the reopen of the app that crashed it. If that is the case you could set a flag indicating that the user is currently logging and then on restart just resume the logging. But again we need to know more about the inner workings of activities/apps which are running and get an automatic update (actually didn't think it could happen).
Edit
Based on your findings I'd say you have to handle the app is shut down in onDestroy etc. or/and make sure you save everything persistently. Then you might need to have 2 apps where 1 listens to the other being re installed and when that happens it starts it up again (there is an interesting discussion here). If you are targeting api >= 12 then the broadcast action ACTION_MY_PACKAGE_REPLACED might also have interest.
Is there a way to get a system notification when an app has been uninstalled?
I would like to maintain a table of all clients' info currently using my app. However, that seems impossible if there is no way to detect this event.
The first solution I can think of is to have an always running service in the background listening for android.intent.action.PACKAGE_REMOVED. But then would that service be killed once the uninstallation process has ended, or would it be stopped just before the process has kicked off? Also even if this is a solution it's has the potential to put off a lot of people when they realise that part of the app is running in the background.
Any suggestions? Thanks!
You could simply do it the other way round and maintain a table of users actively using your app. Just call a webservice at a point in the program that show it is active. If an app isn't used for a certain time mark it as inactive.
The documentation for the PACKAGE_REMOVED action says the following:
The package that is being uninstalled does not receive this Intent.
So you can monitor for other applications being uninstalled but not your own.
So you'll probably need track who is still using your application, not who has stopped using it. If you don't want the overhead of having your own server to do this you could use a free service like Flurry.
From Android document, the app uninstalled by user can't not get
Intent.ACTION_PACKAGE_REMOVE
But we can use other method to implement this feature. We all know that there is a directory named with your package name under the /data/data directory after your app installed by user. If your app is uninstalled by user, the root directory of your app(/data/data/com.example.yourappname) will be removed by system. The remove action happen immediately when user click "uninstall", and the directory will be removed by framework package manager system.
So, we can monitor the existence of your app data directory(which usually /data/data/com.example.yourappname) to detect if your app uninstalled by user.
In order to monitor this directory, we have to fork a detached process from JNI.
In this new fork process, we can use Linux system api inotify(7) or access(3) to determine the existence of app's data directory.
Here is a workable implementation. But it got the permission problem when try to send an intent to start system browser on high version Android device. I have no idea how to bypass this. However the example above is enough for your question.
Hope it will be helpful!
Android doesn't provide an inbuilt function for tracking the app uninstall.
Notification can be used as an alternate way to track the app uninstall. For this send notification on the app and track the status of the notification. Count the number of undelivered notification for a particular time period. If status of undelivered notification doesn't change in that particular time period, then consider that the app has been uninstalled from the device.
For example, i have used a cron script which run every 3 days and check the status of last 10 notifications delivered to the device (2 notifications are sent in a day). If all of these 10 notifications have status "undelivered", then the app is considered to be uninstalled from the device.