I would like to know if there is a way to prevent the last task in the Android Task Stack from being finish(); if the user clicks the back button. I do like that the user is sent back to the Home Screen but I would like the last activity to remain in the stack so if the user clicks on the app launcher from the home screen again it doesn't start the main activity again with a new task stack. My app requires the users to sign in and out of it so if they do sign out I want the task stack to be cleared. Does anyone know if this is possible?
Thanks
This is partially possible changing the implementation of your application as a background Service. Of course, preventing your application from being closed is a very bad practice, actually anything that restricts users from closing an app is a bad practice. As said before, the best way to implement this is putting it within a Service, but this way you should implement at least one mechanism to cleanly close your app (an exit button, for instance), otherwise your users will be in need to force your app to close (and that you won't be able to prevent).
More on this, here.
Related
Background
Let's take the next sceneraio:
the user uses an app X which has multiple activities (like the gmail app).
after navigating the app X a bit, he goes to your app.
in your app, you need to start this X app using an intent, to go to a specific activity within it.
now the user goes to this specific activity on the app X.
the user presses the back button, hoping to go back to your app instead of staying on the app X.
another similar scenario:
the user navigates on your app between activities.
your app went to the background (using the home button, for example).
your app shows a notification that once clicked, it will open a specific activity of your app.
the user clicks on the notification and goes to the specific activity of your app.
the user presses the back button, hoping to return to the app that was shown before clicking on the notification, instead of going to the previous activity on your app that was shown the last time it left it.
It seems that the last step on both scenarios isn't the default behavior.
This is why I've searched what is the best combination of flags for this purpose.
The problem
It seems that the only flag that can achieve the behavior i've described is Intent.FLAG_ACTIVITY_MULTIPLE_TASK (together with Intent.FLAG_ACTIVITY_NEW_TASK).
According to the android API, however, this flag isn't recommended for normal use:
Do not use this flag unless you are implementing your own top-level
application launcher.
...
Because the default system does not include
graphical task management, you should not use this flag unless you
provide some way for a user to return back to the tasks you have
launched.
This information seems as confusing as the rest of the descriptions about intents.
There are other intents flags that I've seen, like Intent.FLAG_ACTIVITY_CLEAR_TASK that achieve a similar result, but they have weird behaviors and/or they use high API
The question
Is it safe to use this flag? Are there any good alternatives to it?
What is the danger of using this flag and what is the meaning of the description on the API of using it?
In your first scenario, if your app needs to start an activity of another app, it can just start this activity within the same task as your application. There is no reason to use any special Intent flags for this (you don't need FLAG_ACTIVITY_NEW_TASK or FLAG_ACTIVITY_MULTIPLE_TASK). In step 5 of your scenario, the user will return to your application (because BACK just takes him to the previous activity in the current task). This is the standard, default behaviour.
In your second scenario, my first response is "that isn't the standard behaviour". That means that users probably won't expect to be able to go back to the task that they were doing prior to clicking on the notification. However, if you really want to implement this, then I would suggest that you create a special Activity that is launched from the notification and this special Activity should have a different taskAffinity than the rest of the Activities in your application. In this case, when the special Activity is launched from the notification, it will not bring your application's task to the foreground. It will just create a new task containing just the special Activity. When the special Activity is showing, the user can press the BACK key and this will return him to the task that he was working on prior to clicking on your notification.
In general you should NOT use FLAG_ACTIVITY_MULTIPLE_TASK. The main reason is that if you have several tasks containing your application (or parts of it), it is pretty much impossible for the user to return to a specific one. There is no way to provide different launch icons or different application names (for the different tasks)(, so that the user will see multiple tasks in the "recent tasks" list, but will not be able to tell which one is which. You will have a hard time cleaning up what you are doing and you will just make more problems than you can deal with. There are about a million side effects of using this flag and for general applicaitons there is just no need to do it.
I'm working on large project, so there is some logic for saving application state, and then opening correct activity(fragment) when it comes from background.
But anyway, I've found that if user navigates through my app and then minimize it - android opens it from background in different ways in following cases:
User taps on app icon (behavior: user see home activity, doesn't matter where he was, when application was minimized)
User select app from android "recent apps" (behavior: user see exactly what he saw, when the application was minimized)
So, what is the difference between launching application from background by this two ways? I always thought, that it is the same mechanism, but, obviously, I was wrong.
Thanks for any answers
You should pay atention on the folowing docs Activity and Tasks. In short words: if user start app from recents you will receive onRestart before onStart (without onCreate it means that your app was just "suspended"). You able to save screen state using onSaveInstanceState(). But in general starting from icon and from recents - different application behaviors and you should provide proper code for this ways.
UPD
As described below root cause of unexpected behaviour was additional lunchmode attribute.
From what I experience as an Android user, both are same.
The difference we usually see is how we close the app
Press back button until app close / finish()
On this state no matter how we open the apps it will go to the main screen
Press Home button
On this state depend on the app. If the app does not handle any Activity the app will same with the first state. But if the app handle something like when onPause() the Activity then finish() the apps, then whatever you open with app icon or recent apps will provide the same result.
Correct me if I am wrong
My app is designed to run as a single instance and the Back button does not allow you to exit the app and return to the Start screen because it is used internally to navigate a hierarchy of screens where each screen can be an activity.
However, an external app can launch one of the app's internal activities. When the user is done with whatever the activity is designed for, the user's intuitive action is to hit the Back button to return back to the calling client. But because I prevent the Back button from exiting, the user cannot return.
I can add code to override this when the code detects that the activity is being launched by a client. The problem however is that if the app closes to return, the user might return to the app from where they left off. But since I closed the app to return to the calling client, the user cannot return back to the app as it was last opened. My app needs to remain as a single instance, so the activity that gets launched cannot be created more than once. Any suggestions on how to return back to the calling client but also keep the app running if it was running when the calling client used one of its activities?
In general, you can programmatically control the back navigation trail. Take a look at
TaskStackBuilder and the documentation for handling notifications Responding to Notifications. It seems that what you're trying to do is control the so-called "back stack". If you use TaskStackBuilder, the behavior will match the platform version you're on.
In pre 3.0 platforms, the Back button went all the way through the back stack to the first task the user did since the phone was turned on. Post 3.0, back does not traverse task boundaries; to get to other tasks, the user clicks the "Recent Items" icon. There's also the "up" icon in an app to navigate to the "beginning" of a task within an app. TaskStackBuilder will "do the right thing" for all versions.
In the current platform version, not allowing Back to exit your app is OK, because Back should only go to the first Activity in the current task. In versions previous to 3.0, not allowing Back to exit the app is more problematic, and I personally wouldn't do it that way, but it's up to you.
What happens when the user clicks Back after an Intent starts your app should be clear from the documentation I've cited. Basically, what you want to do is go back to the previous task.
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.
Can someone point me in the right direction to have an Android Application reopen itself to the forefront after a user has pressed the home key? It should be able to be linked to some kind of countdown (which I already have setup, and runs when pushed to background).
I just can't find the function to force this action
*And yes, this is what the user will want, don't worry, I know this doesn't sound user friendly (forcing open) but in this case the user wants it.
Thanks
I needed the exact same thing before -> an app being displayed upon an event but I was sure I read on the Android developers site that this can't be done and that's what notifications are used for, although starting a new activity does bring an app to front. I found this link however to a NEW_TASK_LAUNCH flag with startactivity that might solve your problem -
http://developer.android.com/guide/appendix/faq/framework.html#4