Will an application launch if it is already running? - android

I am making an app and I am putting the final touches on it and i was wondering, if the user presses the "home" button while the application is running, then clicks on the icon to try to run it again, what will the app do? Will it bring the current app to the front? Will it run a new instance? I am wondering because my app has a lot of threads and if the user was running 2 instances of my app it would kill their battery life.

It depends on the android:launchMode of your activity, set in the Manifest.
With the default setting the system always creates a new instance of the activity in the target task and routes the intent to it.
See the reference for detailed info.

Related

Is there a way to force app relaunch after it was killed by the Android OS?

Simple put: I want the app to relaunch (yes, from the launch activity, like if the user just tapped the icon button) every time Android kills my task because of lacking resources reasons.
The reason is that instead of managing everything that could possible go wrong after the app came back "from the dead", like NPEs, I want to start all over from the beginning.
I've searched for a "good practice" solution, but nothing came across.
Any ideas?
EDIT: I don't want to force the app back to foreground. However, if the user do it, I mean he brings it back to fore by his own free will, if Android killed my app because of resources purposes, I want the app to relaunch.
Sorry for not being clear previously.
Bringing your app to the foreground when it hasn't been explicitly opened by the user is considered a bad practice and discouraged. In fact, it won't be allowed in Android Q, except in a few cases:
Android Q places restrictions on when apps can start activities. This
behavior change helps minimize interruptions for the user and keeps
the user more in control of what's shown on their screen. In
particular, apps running on Android Q can start activities only when
one or more of the following conditions are met:
The app has a visible window, such as an activity in the foreground.
A different app that's in the foreground sends a PendingIntent belonging to the app. Examples include a Custom Tabs provider sending
a menu item pending intent.
The system sends a PendingIntent that belongs to the app, such as tapping on a notification. Only pending intents where the app is
expected to launch a UI are exempt.
The system sends a broadcast, such as SECRET_CODE_ACTION, to the app. Only specific broadcasts where the app is expected the launch a
UI are exempt.
Therefore, I would definitely recommend you to discard the idea.

Android App Icon intent category seems inconsistent

Clicking my app icon will sometimes take me to the launcher activity, but other times it will resume the activity where it left off (emulates the behavior of clicking the application in recents).
I've read (can't find concrete docs about this, other than a one off post from 3 years ago by Diane Hackborn) that after about half an hour, the OS will make sure that when you click the app icon, it will relaunch the app, but sometimes it seems to do this directly after I exit the application (with the home button, not the back button as that will call finish on the activity).
Why is this?
Is there any way to force the launcher activity in the Android OS without killing the app first then restarting it? I need to test how my app handles the launcher activity after the application may already be running.
Android will free up memory whenever it feels necessary. For that, it will kill inactive apps. If your app goes to background, at some point Android will probably kill it. Matter of time.
You can kill your app, or you can make it kill itself when it goes to background. No more options.
in order to make your app kill itself, you should override the onPause() method (which is always called when the app goes to background) and add in it a call to onDestroy().

android hidden app strategy

I'm trying to create an app "hidden" from applications list.
The way i though the user will start the app is through a Receiver listening for NEW_OUTGOING_CALL and intercept a particular number dialed.
The problem is that on new Android versions, this receiver will never be activated if the app never start once. (Starting the application from a BroadCastReceiver (NEW_OUTGOING_CALL doesn't always work)).
I can't figure out a workaround for this problem: the app launcher is totally hidden so the user cannot never launch the app, and the receiver would never be activated if the app will never start.
Is there any other strategy or workaround for hide and launch the app with some kind of secret action?
Create a activity with manifest file pointing it as the the Launcher activity and make it transparent and call its finish method in onCreate. User clicking on that icon will have no idea that the activity is opened. But why don't you show the About application kind of screen in the launcher activity?

It is possible to make a HoneyComb activity unclosable?

I'm developing a presentation style application for HoneyComb Tablets. At one stage the tablet may be passed around a room for people to interact with. If possible I would like to prevent malicious users from navigating away from the current activity.
So far I have overwritten the onBackPressed() to prevent finishing the activity but users can still press the other buttons on the status bar and also leave the app via notifications that pop up.
Any suggestions or possible solutions?
Thanks
1. Make your activity full screen.
2 Use an alarmManager to trigger your activity from a service on a regular interval say 2or3 second (only if your activity is not foreground). For this use a boolean variable and store it using sharedPreference. this value will be true in onReume and false in onPause or in onStop or in onDestroy. And then only start your activity from your service if the boolean variable is false. Now if your user will press the Home button then AlaramManager kick start your activiy again.
3 Make a special button for finishing your service and activity and for cancel the alarmManager.
As far as I know there is no way to capture the home button press, so this is not possible. Not to mention, it would be a bad ui design decision by the dev team. The home button is there so every Android user has a standard way to exit apps. There would be some extremely malicious apps if there was a way to make the user unable to exit an app.
I'm developing a similar application that runs in a "kiosk" fashion for retail stores. When the application launches, it programmatically hides the system bar so you cannot exit. The system bar is restored when the tablet is rebooted. It requires root/su however.

How to close an application when the Home button is pressed

Hi I have application with more than 20 activities.I want to close my app when Home button is pressed.
There is no notion of "close my app" in Android. Android will get rid of your activities, followed by your process, after some period of inactivity by the user.
You could use the launchMode and clearTaskOnLaunch flags on your root activity from your AndroidManifest.xml:
android:launchMode="singleTask"
android:clearTaskOnLaunch="true"
When you again start your app, all activities will be killed.
You don't want to do System.exit() -- that's not how the Android Activity Lifecycle normally works (read this also).
What you should do is move the App to the background with moveTaskToBack(). Android will then keep your app running in the background, and kill it if it's unused and something needs its resources later.
If you want it to close all of the open Activities when your App is no longer visible, you can set noHist = "True" for all of the child activities (leave the main activity with noHist = "False", though). This will make it where instead of reopening your application on the last Activity they were on, it will open it on the "main" activity (i.e. it will be as if they just restarted the app).
Anyhow, read through the following answers for more information: Close application and launch home screen on Android
I have the same problem. Im writing a banking app and am required, by contract, to log off the user (or exit) when the app is put into background. There are obvious security concerns there.
There are a couple of ways Im looking to do this:
1. Intercept home button (and back button for the root activity) key press events to call logoff and/or finish()
2. In the onStop() method, for every activity, detect whether the activity is being stopped due to a new activity being show - if not, assume app is being put to background so logoff and/or finish()
The first may not work if a notification is brought to the front then the user clicks home (I havent investigated yet). Or maybe there are other ways for an app to be put into the background without pressing these buttons
The second way sounds messy & difficult to maintain
Id welcome any other ideas
Drapes
I know android has been designed this way, but it seems naive to think that apps wouldnt want an applicationOnStop event
Hi guys what I understood is that u need to know when app goes in background and how to detect it and if I am wrong plz correct me----
The user can go in background if ur app does not provide any way by pressing Back key or Home Key.
You need to use methods "dispatchKeyEvent(KeyEvent event)" to get home key event or back key event and after getting the event you can execute your task.
you can even restrict user from pressing any key but u can not control the home key.

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