I've requirement for application to set a Buttonin every activity to go back to HomeActivitybut I should Not Reload the content for it, so I need to re-use the instance I already have of HomeActivity, how I could do that?
You should use: FLAG_ACTIVITY_REORDER_TO_FRONT
http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_REORDER_TO_FRONT
If set in an Intent passed to Context.startActivity(), this flag will
cause the launched activity to be brought to the front of its task's
history stack if it is already running. For example, consider a task
consisting of four activities: A, B, C, D. If D calls startActivity()
with an Intent that resolves to the component of activity B, then B
will be brought to the front of the history stack, with this resulting
order: A, C, D, B. This flag will be ignored if
FLAG_ACTIVITY_CLEAR_TOP is also specified.
I used FLAG_ACTIVITY_CLEAR_TOP for home button in my activities. If you have your HomeActivity already in application stack, this flag causes close of all activities above your HomeActivity. It depends if you need to reorder HomeActivity to front (Back button will return you back to activity where you clicked home) or you want to close all activities that are above HomeActivity (like clicking back until I'm in HomeActivity, in my case Back button closes application from my home activity).
http://developer.android.com/reference/android/content/Intent.html#FLAG_ACTIVITY_CLEAR_TOP
Related
I have two activities A & B. in A, i am showing a list of titles, and on clicking a title, it will open the detailed article in activity B.
I declare A as singleinstance in Manifest.
But if I declare A as single instance, and when the Activity B is opened and paused, then Activity A is not available on backstack.
I will try to explain by reproducing:
Activity A (launchMode = SingleInstance) with list of titles.
On clicking a title, Activity B opens
On clicking back button/up navigation, Acitiviy B finishes and Activity A resumes.
Again open activity B.
Press home button of device (Activity B goes to background - onPause)
Activity B is available in Recent Apps
Open app from recent apps/launcer - Activity B opens
Clicking back button/up navigation - Act B finishes, but Act A not resumed.
How can I provide better up navigation?
For my idea, you can change lauchmode of Activity A and Activity B from Singleinstance to android:launchMode="singleTop". I work fine for me. It is well said here. Let try.
When you will press the home button the activity B would call onStop() method. For a better understanding you can refer to https://developer.android.com/guide/components/tasks-and-back-stack.html
I would like to ask similar question to:
Go back to previous screen without creating new instance
However I don't want Activity A go through onCreate callback, I would like to return to previous instance in the same state. How to achieve that without calling multiple finish() ?
There's no need to finish() activities as you navigate through your application. Instead, you can maintain your Activity back-stack and still achieve your goal. Let's say you have 4 activites like so:
A --> B --> C -->D
where D is the topmost activity and A is root activity. If you are 'falling back' to activity B, then you'll need to do two things in order to avoid hitting B's onCreate method.
1.) Make B a "SingleTask" activity. You can do this in the Android Manifest. To be brief, this means that only one 'instance' of B will ever exist within this Task. If B is already running when it's called then it will simply be brought to the front. This is how you do that.
<activity
android:name=".ui.MyActivity"
android:launchMode="singleTask"/>
But you don't want to just bring B to the front. You want to 'fall back' to B so that your stack looks like
A--> B
2.) Add this flag to your intent that 'starts' B. This ensures that C and D are removed.
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
Now when 'D' calls new Intent to B, B will be resumed and C and D will be removed. B will not be recreated, it will only call onNewIntent.
When navigating from A to B do not finish Activity A.
When navigating from B to C finish Activity B.
When navigating from C to D finish Activity C.
So from wherever you navigate back finish current Activity and Activity A will get resume again not get created.
I have an app that starts with Activity A. Among other things user can go to Activity B and return with the back button.
User can start Activity A also from Activity B using a Menu. This brings Activity A to Front again.
intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
Problem is: Activity A should be Home Activity. Pressing back needs to always quit the application.
Currently back will go back to Activity B, then finish.
Using FLAG_ACTIVITY_CLEAR_TOP will destroy Activity B, which I do not want as the user should find the activity where he left it (e.g. scrolling position; unless android destroyed it for memory reasons).
I just want to leave the application on back pressed on Activity A. How can I do that?
Can I clear the backstack without destroying the activities?
As an alternative I could override onBackPressed in Activity A to quit the app, but how do I exit the application? Using finish() will only close current activty an bring back other open activities. Do I nees a broadcast as suggested here: Clear Activity back stack?
I have a widget for my application, which need to be somewhat independent from the app.
The activity workflow should be like this:
Widget -> Activity acting as receiver
Receiver -> LoginPage or Activity A (depending on login status)
LoginPage -> Activity A
Activity A onKeyDown -> Activity B
Activity B onKeyDown -> Home Screen.
I have no problem until Activity B, which sends back to Activity A when I press onKeyDown. I'm using FLAG_ACTIVITY_CLEAR_TOP flag and finishing the Activity when starting the activity B.
When I move from ActivityA to ActivityB using the CLEAR_TOP flag, I supposed that Activity stack is cleared, then in ActivityB I finish the Activity on the onKeyDown() method, assuming that the App will be closed, but it doesnt. Why?
I'm also trying to use FLAG_ACTIVITY_CLEAR_TASK and FLAG_ACTIVITY_NEW_TASK in the receiver but I dont understand the mechanism pretty much. Any idea about this?
In fact the FLAG_ACTIVITY_CLEAR_TOP, start your activity B if its not started or it came back as the second activity on the BackStack. To finish Activity A, you can call finish() after starting Activity B or add no history flag, when starting A.
#JesusS: I doubt if u can finish ur activity in that fashion during a forward transition.
Consider a scenario of moving from Activity A to Activity B. Now if u want to kill Activity A and want to move to Activity B then call the startActivity(intent);
(where ur moving from activity A to B)
without any flags on the intent followed by the finish() on activity A.
As per my understanding u can use Intent.FLAG_ACTIVITY_CLEAR_TOP only during backward transition i.e when u already have that activity on the stack.
Consider the following scenario:
A --> B --> C --> D
Now if u want to move back from activity D to Activity A by clearing the activities u can go for Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP.
The result is that the Activities D, C, B(LIFO) will be removed from the stack and the activity A resumes by calling the onResume() of Activity A.
Support App starts activity A, then A starts activity B and finishes itself. After that activity B starts activity C.
Now the stack contains B and C, with C at the top.
Then I click a button in activity C, and want it to clear B and C and start activity A, i.e. I want activity A to be the only activity in the stack. How can I make it?
Edit: I made a test to use FLAG_ACTIVITY_CLEAR_TOP. But it didn't work in my case, because activity A is not running when button in activity C is clicked.
Set the FLAG_ACTIVITY_CLEAR_TOP flag on your intent to start activity A.
Edit: Is there a reason you can't leave A going? Then you could do as suggested.
Otherwise, another (more complicated) option:
In B start C forResult. When A is started from C, you could finish C with a result indicating to B to also exit.