I have 3 activities ( say A, B, C were A-is the Launch activity). When I press home button when at activity C, app goes into background. After that, I took my app through all apps list menu. At that time, my launch activity is showing (activity A). When I press back button, It goes to previous activity (C). I want to retain in the same activity (C) while coming back from background. When I run application through Eclipse, It works fine. But when I send Apk file through mail and run it in device, It fails (previous problem occurs ).
I tried with
android:launchMode="standard"
AND
android:alwaysRetainTaskState="true"
in my launch activity (Login activity or A). Any body please help me, Thanks in advance.
Follow following steps to insure that you are following the right practice:
1. Make sure you are using finish(); on the Activity A or B if you want to finish it and dont if you want the back button functionality.
2. Try Implementing onpause() and onresume() even if you are not going to perform any functionality in them. Use super() for them there.
3. Also, in android when you start an activity by clicking on the icon instead of resuming it from already running activities, it exhibits a different behaviour.
Related
I have a series of Android activity A-->B-->C-->D while in D if I press the home button and click on the app icon, the app starts from Activity A, I clear the previous activity and call finish on each activity and I have tried the launch modes Single task and Single instance, but in vain. Please suggest.
I fixed this issue. The problem was Activity D had a task affinity.
android:taskaffinity="". I removed this statement in Manifest. Now the app shows the Activity from where it was left at.
The main/launcher activity in my app is a login page (Activity A). Once the user is authenticated, they are taken to the main area of the application, e.g. Activity B. So now the current activity stack of this task is A > B.
I then press the home button on the phone and am taken to the Android home screen. I re-launch my app via short cut key in HTC Desire Z(See Image after Space there are two Short Cuts 1 and 2), and I am taken to Activity A, instead of Activity B. Either the activity stack is now A > B > A, or there are now two separate tasks with activity stacks A > B, and A respectively. What I want is to be taken back to Activity B when I relaunch the app..
I followed this link
The above solution worked for 2.3.3 but in ICS 4.0.3 it has an issue that i am not taken to Activity B.
How do i resolve this,In ICS I am not able to see the what Intent flag system is using to launch activity when short Cut is Pressed,is this a System BUG?
Please Help
NITZ
The pattern that I tend to use for the login like this. I'll use A to mean Login and B to mean Main application.
I make B the launcher Activity, and in its onCreate() I check if a login is needed and if so, then I immediately launch Activity A. Once A is done, i finish() it, so that I'm back to B.
This way my activity stack stack never contains the Login activity, except when it's being used. ie, after a Login is done, then only B is on the stack.
In my situation, there is one case in which I need to make sure the activity only runs one at a time.
I found if I set the LauchMode of the activity, I can reach the single instance aim, but it won't update the view of the activity.
This activity is launched by startActivityForResult, and we send the URI with the intent to the activity.
Let's discuss with this certain case:
gallery - lauch this activity with imageA.
camera - lauch this activity with imageB.
My request is not to destroy the old activity, but the activity that just received the new intent infomation should refresh the view.
I found a new method, onNewIntent.
This method can refresh the intent before resume. I will try it.
You can have an Activity with a manifest attribute of singleInstance.
As soon as the activity is relaunched , onResume gets called. You can update the view with the new image and invalidate the older View.
<activity ..
android:launchMode= "singleInstance" />
In your manifest, use android:launchMode="singleTask" instead of android:launchMode="singleInstance". Using singleInstance only returns to the existing instance if it is at the top of the stack. singleTask, on the other hand, return to the existing instance of the activity, as it is always at the root of the task.
Then, when your instance is launched, override onNewIntent to update your UI according to the new intent.
Refer to the Andorid documentation for details.
Be careful when using android:launchMode="singleInstance" in multiple activities application.
Here is my test on Pixel 4XL (Android 10)
Example, we have 3 activities (without declare taskAffinity)
A (entry activity)
B (start from A)
C (singleInstance, start from B)
If we start A->B->C. Now A,B in a task and C in a different task.
From C, press back -> will see B, press back -> will see A, press back -> app close. Everything working efine.
However, if we start A->B->C then press Home -> app go to to background.
Now there is 2 situations
User open app again from Recent app.
User will see C screen. Press back -> app will close (don't go to B)
User open app again by click on app icon
User will see B screen. Press back -> will see A, press back -> app will close (don't go to C)
The behaviour after open application is different between both case. But in both case, the application is always available in Recent app and you never able to remove application from Recent app (after remove it will appear again). Only able to remove it by Force stop in Setting.
If you run adb shell dumpsys activity activities, you will see that activities still exist in Stack, but you can not go back to it.
Another case
If we start A->B->C->A. Now A,B,A in a task and C in a different task (A is current visible to user).
From A, press back -> will see B (not C), press back-> will see A, press back -> will see C, press back -> app will close. (at least here we can go back to C)
Now if, we start A->B->C->A then press Home. In both case, user open app again by Recent or click on app icon, user will see A screen. Press back -> will see B, press back -> will see A, press back -> app will close (never see C screen)
Another note
The above example, although application run on 2 tasks but in Recent apps, it only show 1 task.
If you set the taskAffinity, in the Recent apps, you will see 2 tasks. In that case, you can choose the task which contain activity that you want to display but when you press back, it just go back to the activity in same task or close app (not able to go back to activity in another task).
Also, if you click on app icon to open app again, we have the same behavior like above demo.
I think singleTask and singleTop is less complex than singleInstance, so if it is enough for solve your problem, consider to use them instead of singleInstance
The problem is somewhat odd and after having trying to figure it out for about a day now, I am posting it here.
I have an application where an activity A(main activity) launches other activities(B,C or D).
The issue here happens when activity A has started Activity B and 'home' button is pressed.
Case 1 - When I test my application in debug mode on my device (HTC Desire) after pressing the 'home' button, I again click the application icon, it returns to the same activity (activity B), which is what is should do. No issues here.
Case 2 - When I export the signed package, and then install the application on the same device, then if I click the application icon after pressing the 'home' button, then a new instance of activity A (main activity) is launched ON TOP of activity B. I got to know this because when I press 'back' from that activity, it returns to activity B and pressing 'back' again shown activity A.
The behavior ceases to exist if the application is quit in the same order it was started, that is, if I press 'back' from activity B, then 'back' from activity A (exit).
After this everything runs fine.
I have tested it many times with different settings but I can't seem to figure out why the behavior is like this.
Any help is appreciated.
I think giving Activity A the 'single top' flag in your manifest should fix this.
Regarding Case 1:
When launching your intent from Activity A to start Activity B, add the flag FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET
This will ensure that when you go home and launch the the app again, Activity A will be shown.
Regarding Case 2:
I'm not exactly sure how this would occur. It seems like it thinks you have two versions of the app, the signed one and the unsigned one but keeps them both in the same task stack. You may want to consider using singleTask or singleInstance for your Activity if you only want one instance. See the doc on tasks and back stack for more details.
I would agree with Noel regarding the likely cause of Case 2. Without task reparenting or it being set to a launchmode preventing multiple instances of an activity, there is a chance that launching it from Home isn't deemed the same stack as launching it from Eclipse (assuming this to be the case).
In my talent calculator app I have the whole application set allowTaskReparenting=true to ensure nothing is left in other stacks (primarily email as it can email launch urls). I then have my main activity set to launchMode="singleTask" as I only ever want one instance of this to exist no matter what launches it or with whatever intent.
My only other activity is for loading and saving and that has noHistory="true" to make sure it is removed and never returned to. That basically means it only exists while you're in it, and can never return to it.
clearTaskOnLaunch="true" will also ensure only the main Activity remains in the stack when it's launched from Home, but this isn't always the case if you have other ways to get into your activity. If it's only ever launched from Home then set this.
Hope that all helps.
Do you start you application manually or using Eclipse or another IDE? When starting from Intellij IDEA I had exactly the same problems. Then I stopped and ran it manually and behaviour was as expected.
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.