I have a SearchActivity that is defined with android:launchMode="singleTop" in the manifest.
My SearchActivity includes a SearchView for the user to enter their query and a ViewPager to show the search results.
I chose single top for SearchActivity, so the use can make loads of searches in the activity and then only has to press the Back button once to get back to the home screen.
However, I have just introduced a "SmartSearch" button into the activity which, when pressed, will trigger an automatic advanced search with the results still shown in a SearchActivity.
The requirement, though, is that I need these advanced search results to show up in a new activity on the stack - i.e., so the when the user presses Back, they will be taken to the previous (standard) results screen, and then must press Back a second time to get back to the home screen.
I've read this about launch modes and this about tasks and back stack, and have tried launching the 'advanced' SearchActivity using an intent like this...
smartSearchIntent.putExtra(SearchResultsActivity.QUERY_EXTRA_KEYS, selectionArgs);
smartSearchIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
...and I also tried using Intent.FLAG_ACTIVITY_NEW_TASK as the parameter, but when I press Back on the advanced search results screen, it just jumps straight back to the home screen.
All the while, I have android:launchMode="singleTop" defined in the manifest for this activity because that is the 'normal' behaviour - so is it possible to override this and, if so, how?
Or is there a better solution?
I worked out a solution / workaround for this. Have just posted my answer for someone with a related problem, here - https://stackoverflow.com/a/27125107/1617737 .
Related
The official Dev Guide of Tasks and Back Stack says, activities can be instantiated multiple times, and Home Activity is taken as an example
So I tried it out as the graph illustrates:
Launch Activity 2
Press Home button
Launch Activity 1
Press Back button (so I return to Home screen)
Press Back button again
But I did not go back to Activity 1. Thus, it seems that Home Activity has not been instantiated multiple times. Is it so? If so, how is it kept in a Back Stack?
EDIT: Sorry, I should've clarified earlier that I didn't write any codes to test it. All I've done is just launching applications on favorites tray. I'd better go to read the source code and search for the behavior of Home Activity.
Anyway, I don't think Home Activity is a good example here to illustrate multiple instances.
Your issue might be that you might have called finish() in your Activity2. Or, the OS clears up the 2nd Activity before you return back to it. The behavior you are trying to attain on your own has no guarantees. You can't force an Activity to keep running so that you can return back to it.
I'm ware of androids life cycle and that it's not needed to add a "exit" button in the application.
But still, this back button stuff isn't really working out well.
You maybe know this issue from the default SMS-App that android comes with: you open it when you get a new message and exit it using the menu button or something else.
After like 20 times doing this, you then decide to exit the app using the back button, what happens? you have to go back though 20 views. every time you press back you return to the "all messages (by sender)" listview and when you press back there again you return to the message opend 20-1 (message 19). again you press back and return to the listview and again you press back and end up at message 18. till, after40 times pressing back, you finally exit the messanger app.
same happens when for example you got a action bar with a "home" icon which opens the main screen of your app. the user picks a action and the new activity starts. than the user clicks the home button and returns to the main screen. when pressing the back button - no matter if you call finish() in the onButtonBack listener or not, you the user would expect the app to exit, but in fact the app returns to the previous activity which is wrong.
such cycleing may happen for various reasons, thats why - even thought i'm aware of the supposed to be lifecycle of android - i wan't to EXIT (& destroy) the app when pressing back within a defined activity.
calling finish() dosn't help. if there's a previous activity it will re-open it. calling system.exit(0) isn't nice to do.
so: whats the right way to prevent such back-press-cycles and/or exit a application (WITH destruction)?
for better illustration of what i want to achieve: consider A, B, C being activities. a arrow (-->) illustrations a new intent call from the activity leftside of the arrow, rightside of the arrow represents the activity that is called. ex.: A --> B means activity A starts activity B. now here's what i want:
1) A --> B --> C pressBack:--> B pressBack:-->A pressBack:--> Exit
2) A --> B pressBack: --> A pressBack: --> Exit
3) A --> B --> A pressBack:--> Exit
as you see, back works as always, BUT when in activity A it exits the application.
the behaviour i got now is 1) and 2) as above but
3) A --> B --> A pressBack:--> A pressBack: --> Exit
keep in mind, i've already overwritten the onBackPressed listener of activity A with a finish() call. even calling system.exit(0) dosnt work. however, even if it would: its not what i want, i want the REAL way to do it android style - i cant imagine system.exit(0) is best practise.
Well this is the default behavior.
If you have another approach, just implement it.
One approach to deal with this is to use the android:launchMode="singleInstance" for activities that can be launched in a singleton manner (only one activity can exist)
For example, if the SMS page in the SMS app was a singleTop, it would have needed only one back press to remove all the SMS pages. It is a matter of choice
Another more aggressive way would be to finish Activities when you start another activity. Of course, such decision would risk making the app less friendly (android users are not accustomed to this behavior). Nevertheless, if this is used only where it may be considered acceptable then it might be acceptable.
A very acceptable place to do this would be a login screen: Once login is successfull, you start another activity (probably designed for logged in users) and finish the login activity.
Enjoy Finally, in my personal opinion, you can add an Exit button. Users will find it nice.
Check my post: Adding an Exit button to Android Application
I have a search feature with a list view. When the user click on search and filters the result the activity is loaded from the beginning. So here is the flow.
User opens my application (Gets the whole list ot items) -> Search1 (Filtered search) -> Search2 (Filtered result 2) -> Search3 (Filtered result 3). Now when the user clicks back he goes to Search 2 -> then back to result 1 -> then back to the mail list.
This is how is my application working now. I want this to change as when users is on any search result I want him to go back to main list without going back to any search results.
Basically I dont want android system to track the search results so that when user clicks back, he should directly go to the main list.
How do I do this. Please advice if you have any alternative for this. Thank you for your advice and time. Thank you.
You should set your search activity to be android:launchMode="singleTop" in your manifest, that way there's a single search activity and you're only responding to search intents within it. This is actually the "ideal" behavior according to the docs.
When you are done with the search results you could finish that activity. You might even be able to use finishOnTaskLaunch to achieve the same thing and it is probably more desirable too.
I'm using a custom Launcher application with Widgets that are used to launch (and provide status updates) for an application.
The application consists of a few Activities - let's call them A, B and C for simplicity.
A is the launched Activity. The user proceeds from A to B and then to C (never in any other order).
At any time the user can press the 'Home' button on the remote control and return to the launcher application.
If the user then presses the 'Back' button on the remote control they always return to the Activity they were last using (A, B, or C).
However, if they click on the widget (rather than pressing back) the Activity that is brought to the front seems inconsistent!
So, here is an example of what happens
From (custom) launcher, use widget to launch application
Activity A appears
User presses a button that launches Activity B
Activity B appears
User presses 'Home'
Launcher appears
From (custom) launcher, use widget to launch application
Activity A appears NOT B
Sometimes I get Activity B instead of Activity A - but I'm not sure under what circumstances. I want to get the Activity at the top of the stack to be displayed and never any other Activity (Activity B in the example above).
I've read Google's documentation about the Activity flags ("single-task", "single-instance", etc...) but nothing seemed to jump out as the solution to my problem.
In my case, Activities A, B, C only make sense when run in that order - and it never makes sense to see a previous activity unless you explicitly go back to it.
I'm not sure if the problem is the way the widget is launching the application or whether there is something I need to specify in my manifest or something else.
Any ideas?
Thanks,
Dan
Isn't that what's supposed to happen? Isn't your widget launching activity A? Would you expect it to launch activity B if you are asking it to launch activity A?
(Althought you say that you get B launched sometimes. Isn't this related to the app being forced out of the memory?)
I'm sorry, but this is not an answer, but rather some additional information related to that same question.
I have found a pattern for Activities when relaunched after home button is pressed.
See my question for all my research:
Android Activity Stack is not working as stated in the docs - last activity in task stack not shown
Hope this can be of help...
I have been reading that the suggested fix for this strange behavior is the use of a "Dispatcher" class as Main that will launch the activity based on the application state...or you can also keep track of all the activities opened that need to be restored...but this can become really cumbersome when having a complex UI application design.
I'm experiencing kind of strange behavior of my application after hard Home button is pressed.
When you press Home, everything is OK - my app goes to the background, showing Home screen. But if you try to choose my app in the main menu or in the list of last tasks it behaves like it was not started before and does not show the last activity you were on - it just starts from scratch, namely, shows the splash screen and starts next corresponding activities. Moreover, old activities of this app remain on the activities stack, and previous instance of the app is not terminated - so if you press Back for a few times you'll just run into those activities which were undoubtedly started during the previous session of work with my app. Splash screen activity is filtered by "android.intent.action.MAIN" filter and "android.intent.category.LAUNCHER" category.
The strange thing is that all of that happens despite the fact that I do not intercept any Back key hits, or override any onPause or onResume methods. What's happening contradicts with my understanding of Android app lifecycle - I was sure that when you hit Home an app just goes to the background, and when you choose it in the menu later - it just unwinds and does not start anew. (Of course, unless stuff like that is stated in the app manifest or corresponding methods are overridden or something else).
I also checked it for some other lifecycle events - such as changing orientation or flipping hard keyboard out - and none of those led to such strange results. It appears that the problem occurs when you try to start the app from main menu or menu of last applications.
I hope you will be able to help me. Any advice on what to pay attention to or where to search for solution would be really great.
Regards, Alex
You need to set android:launchMode="singleTask" in your LAUNCHER activity in your manifest file.
For more info on the launchMode attribute see here
Note that:
The default mode is "standard".
and:
Every
time there's new intent for a
"standard" activity, a new instance of
the class is created to respond to
that intent.