Some Android application restarts automatically when i kill process manually.
How this can be possible?
Is there anyone who know how to do like this on Android platform?
Are you sure these applications are restarted automatically?
I suspect that they actually have a few activities on top of each other. When you kill a process in Android, only the top activity will be destroyed, other activities are still on the activity stack. In other words, when you return from the "process killer activity" another of the application's activity becomes visible, and the process is restarted.
This is not something that you need to implement in your application, it is just how Android works.
Related
As we know Android would kill a paused Activity in some conditions. And there is a FIFO back stack of Activities.
My questions are as follows:
How Android kills an Activity without pulling it from the back stack (it might affect the top active Activity)
After killing it, what things are released from this Activity? And can I still get this Activity's instance?
Android does not kill Activities "separately", it kills the whole app process with all Activities.
The only way to get an Activity killed by the system is to set Don't keep Activities flag in device's Developer Options. However this option is just for development, not for applications in release.
Activity can't be killed but Os can kill the whole application. In this case you can try finish()/finishActivity()/context.finish() to finish the activity. While you finish an activity backpress will not return to the previous activity.
System can't kill activity, it can call the whole app.
And when it kills the whole app, it doesn't call any method from activity (onStop(), onDestroy(), etc)
Finally, you can't get activity instance.
I would like to simply stop the app, and all its activities and services. Currently, from my main activity (which had started other activities), I call finish(), and the app appears to stop, as it goes to the home screen of my device. However, when I check running apps on the device, this app is still listed. It says "one process, and one service". Is there a way to just kill everything? Or, if I have to do it individually how would I find what is running, and how do I stop it? thanks
Is there some specific reason you want to make sure the process is killed?
Android manages processes intelligently. It keeps your process around, and if the user starts your app again it can use the existing process, rather than start up a new one. And if your device start running low on memory, Android will start killing off these inactive processes to free up resources.
In short, it's a good thing that Android keeps your process around. You shouldn't want to have it killed needlessly.
Although it sounds like you may not be stopping your application's service. If you use bindService to start the service from your activity, the service will automatically be stopped when the Activity is stopped (assuming nothing else has bound to the service). Alternately, if you use startService to start the service, you need to call stopService to stop it.
I just did a little test: I started my app, went to a certain screen, pressed the home button and killed the process via Advanced Task Killer.
Now, if I go back to my app just a few moments later, I come back to that very screen. I also know that onRestoreInstanceState() is called in this case, as I have played around with this method quite a bit.
However, just out of curiosity, I did all the same, but let my phone lie around for some time (an hour or something). When I restarted my app, it went straight to the main activity.
So my question is: for how long does Android keep the saved state? or what determines if it throws it away or not? I already figured out it had nothing to do with lockscreen on/off.
Kind regards,
jellyfish
The activity is restored because such applications as Advanced Task Killer use "illegal" methods for killing applications. Android kills application is a similar way when it's low on memory and when killed application is launched again its state is restored.
Android keeps an application state for some time. Usually it's about 15-30 minutes but I think it depends on the device. But you can ask Android to keep an activity state "forever" (until the activity is finished) using android:alwaysRetainTaskState="true" attribute.
When you killed an application with Advanced Task Killer for example, the application restart with the main activity the next time. I suppose that the application save the state in file to restore the same activity even if it killed!
Android will dispose of the activity when it needs the resources that the activity is holding (usually memory) and the activity is not in the foreground. There's more criteria involved, but that's the general case. There's no predefined time limit or criteria other than "when it decides it needs to". The app could die almost immediately or it could stay up indefinitely. You should never assume your app will ever be killed and you should never assume your app will never be killed.
Well apparently my android application doesnt close when I finish the activity so it there a way to force close it including any activity in my app that could be opened?
The fact that the process is still alive does not mean that the Activities did not finish. The process might be kept for a while until the OS decides to kill it.
If you have activities that do not finish properly, make sure that you did not leave a thread running.
There is no method in the API to close an Application. It is up to the OS to terminate it when it is convenient. The last resource is to kill the process, but you should never need to use that in your apps.
Make sure that threads that you have started terminate, and then invoke finish
Btw. How have you verified that you activity isn't closing?
Call finish() at the point when you want it to close. For example in onPause() if you want it to finish when the activity is no longer the topmost one.
I personally suggest you simply make sure your app does not do anything when it is not active and let the system worry about 'finishing' it.
We know that when the system runs out of resources, an activity in background serializes its state and gets killed by the OS. When we resume it, the OS recovers the activity state by savedInstanceState passed to onCreate method. Considering we are responsible for handling what is going to be serialized/recovered, I'd like to have my activity killed in order to test the code I created for recovering. How can I achieve that? Forcing the application to be killed through the applications menu doesn't help.
Rotate your device (or emulator). Android saves, destroys, and re-creates the activity in the new orientation.
Download a task manager that kills the process in a less destructive way than "Force stop" in "Manage applications" settings. Example: GO task manager.
The task manager will kill the app (and the debug) but somehow not the activity stack (don't know why).
When you'll relaunch the app again, onCreate will be invoked with the last saved bundle/state.
The disadvantage of this solution, compared to Darrell's, is that you cannot debug it.
The advantage of this solution, compared to Darrell's, is that it is more close to real life scenario.
You can kill it from Eclipse also.
Go to the Android view. YOu should see the list of processes in the Devices tab.
Click on your process and then click the little "STOP" button.
Instant death!
FYI you can also attach the debugger this way by clicking on the little green bug