When I am starting a new activity do I need to explicitly finish the current activity or does android take care this ?
This is what I write in activity A to start activity B:
Intent intent = new Intent(this, BActivity.class);
startActivity(intent);
Should I end A by calling next line after above mentioned two lines ?
this.finish()
In General no you shouldn't.
The difference will be if you call finish in Activity A, While the user is in Activity B if they press the back button they will go back to whatever they were doing before opening your application. If you instead do not call finish in Activity A they will go back to Activity A
If you DO call finish:
Activity A -> Activity B -> [user press back] -> Homescreen (or whatever activity is on the stack below activity A)
if you DO NOT call finish:
Activity A -> Activity B -> [user press back] -> Activity A
No it is not compulsory.
finish()
finish method state that "Call this when your activity is done and should be closed. The ActivityResult is propagated back to whoever launched you via onActivityResult()."
reference link >> link
explicitly finish the current activity or does android take care this ?
It depends on your requirement if you wants activity A while coming back form activity B still there so you need not to call finish but if you does not want activity A when coming back form activity B then you should call finish ....
Related
I have an application with several Activities in Android A,B,C,D. I have a question about the back stack.
A->B->C->D it is a normal sequence.
My question is : when i press the back button in Activity D, i have to go to the Activity B, not back to ActivityC. Since ActivityC have some imageView i want to save, i don't want to use noHistory to destroy the ActivityC. it is possible to do that
A1->B1->C1->D1
the back stack should be: D1->B1->A1 . C1 saved some imageView and if C1 launch again, the imageView in C1 will contain the same images. Is it possible just modify the code in ActivityC??
thank you
You should call finish() in activity C after, starting of activity D
startActivity(intent);
finish()
Handle onBackPressed() of each activity. So that after back pressing on D, it will redirect to B, then similarly to A.
Use onActivityResult() methods of an activity:-
Here is how it will work -
Use startActivityForResult() method while you are starting activity
While when you are going back
Activity D - before finishing write -
Intent i = getIntent();
setResult(RESULT_OK);
finish();
Your D is finished and c's onActivityResult() will be called - save your data and call finish() with above methodology, It will go to B's onActivityResult().
I have a 1st and a 3rd activity. I wish to push a button on the 3rd activity and it finishes the 3rd and 2nd activity switching all the way back to the 1st activity(it's the MainActivity might I add). In other words, is there a way to finish automaticly the call stack of activities to a specific activity?
You can use method startActivityForResult() to start your activity.
You need to call method setResult() when you finish the activity.
And override method onActivityResult() to do what you want to do.
Actually, seems 2 methods can solve this.
Assuming Activities: A -> B -> C, and all alive in the same stack.
1) Use android:launchMode="singleTask" for Activity A. When C calls A, A starts and both B & C finish.
2) When starting A, adding flag Intent.FLAG_ACTIVITY_CLEAR_TOP.
if you don't have to pass any data to the main activity, i guess this is what you are looking for: how back to the main activity in android?
execute this code at the button click in your 3rd activity:
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
this code clears your activity stack and reopens your main activity.
I am new to Android . Here I have for activities A,B,C,D in which A is the Home Activity.It is in stack as A->B->C->D
When I press back from B or C it should go back just as normal. But if I press back from D it should go back to A and from A the app should exit
I guess you could intercept onStop() and guessing if the activity is switching to C and launching A instead. But it would result in a hard to maintain mess and I do not recommend that.
However, if for some reason you still not want to override onBackPressed and you manage to guess that D is stopping because back was pressed (without overriding onBackPressed(), just start A activity from there with an Intent with FLAG_ACTIVITY_CLEAR_TOP (call i.setFlags(FLAG_ACTIVITY_CLEAR_TOP) )
According to the doc:
If set, and the activity being launched is already running in the current task, then instead of launching a new instance of that activity, all of the other activities on top of it will be closed and this Intent will be delivered to the (now on top) old activity as a new Intent.
So A will be brought back and B and C will be cleared.
when you start your new activity finish the old activity for example if you want to start C from B :
Intent I = new Intent(B.this , C.class) ;
startActivity (I);
B.this.finish();
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.
I have 3 different activities in a TabGroupActivity. Let's say A - Parent, B - Child 1, C - Child 2.
A --- starts --> B
B --- starts --> C
and I have an alert dialog in C which shows some message. I want to go back to activity A when I press Ok button on dialog.
But the problem is that I can open activity C from other activities too and I want to go back to their parent activities too. So I need to make something which will work no matter which activity opens C. I've tries with this one but didn't work :
Intent intent = new Intent(Synchronization.this,Synchronization.this.getParent().getClass());
but it didn't help me. Any suggestions?
You just have to make use of two Activity methods viz. startActivityForResult() and onActivityResult()
Example : http://www.vogella.de/articles/AndroidIntent/article.html#explicitintents
Here goes the logic :
In ActivityB
Start ActivityC by using startActivityForResult(activityCIntent,INT_CODE);
In ActivityC
Now check if Dialog's OK Button is pressed, if yes then set the result using setResult(RESULT_OK,intent); and then call finish();
Then control will be redirected to ActivityB's onActivityResult() method.
Now inside onActivityMethod() check whether result_code==RESULT_OK and requestCode = INT_CODE. If yes then simply call finish();
In the Activity B start the C Activity as startActivityForResult() so when you finish the C activity it will back to the B with result. As the result you may pass flag with the intent object.
Now when you finish the C activity with ok button then set the result as RESULT_OK into the setResult() if you need to pass the data back to the B activity you may set the data into the Intent add this intent with the setResult() method and then finish the C Activity.
Now in B check the requestcode is from the C then finish this Activity. As you start this C Activity you can also start the B Activity for the A Activity.
And you need to override onActivityResult() in B activity and if you start the B Activity as for result then also you need to define also into A Activity