How do you use Intent FLAG ACTIVITY CLEAR TOP to clear the Activity Stack

Question

I ve read through several posts about using this  but must be missing something as it s not working for me  My activity A has launchmode  singleTop  in the manifest  It starts activity B  with launchmode  singleInstance   Activity B opens a browser and receives and intent back  which is why it s singleInstance  I m trying to override the back button so that the user is sent back to the activity A  and can then press Back to leave the activity  rather than back to activity B again      activity B  Override public boolean onKeyDown int keyCode  KeyEvent event      if  android os Build VERSION SDK INT  lt  android os Build VERSION CODES ECLAIR    amp  amp  keyCode    KeyEvent KEYCODE BACK    amp  amp  event getRepeatCount      0  onBackPressed     return super onKeyDown keyCode  event      Override public void onBackPressed      startActivity new Intent this  UI class    setFlags Intent FLAG ACTIVITY CLEAR TOP   Intent FLAG ACTIVITY NEW TASK     return      After returning from the browser  the stack is    A B Browser B  I expect this code to change the stack to    A     so that pressing back once more takes the user back to the Home Screen   Instead it seems to change the stack to    A B Browser B A    as though those flags aren t there   I tried calling finish   in activity B after startActivity  but then the back button takes me back to the browser again   What am I missing  Thank you

User · Answer

i called activity name this finish   after starting new intent and it worked for me   I tried  FLAG ACTIVITY CLEAR TOP  and  FLAG ACTIVITY NEW TASK    But it won t work for me    I am not suggesting this solution for use but if setting flag won t work for you than you can try this  But still i recommend don t use it

User · Answer

I know that there s already an accepted answer  but I don t see how it works for the OP because I don t think FLAG ACTIVITY CLEAR TOP is meaningful in his particular case   That flag is relevant only with activities in the same task   Based on his description  each activity is in its own task   A  B  and the browser   Something that is maybe throwing him off is that A is singleTop  when it should be singleTask   If A is singleTop  and B starts A  then a new A will be created because A is not in B s task   From the documentation for singleTop    If an instance of the activity already exists at the top of the current task  the system routes the intent to that instance      Since B starts A  the current task is B s task  which is for a singleInstance and therefore cannot include A   Use singleTask to achieve the desired result there because then the system will find the task that has A and bring that task to the foreground   Lastly  after B has started A  and the user presses back from A  the OP does not want to see either B or the browser   To achieve this  calling finish   in B is correct  again  FLAG ACTIVITY CLEAR TOP won t remove the other activities in A s task because his other activities are all in different tasks   The piece that he was missing  though is that B should also use FLAG ACTIVITY NO HISTORY when firing the intent for the browser   Note   if the browser is already running prior to even starting the OP s application  then of course you will see the browser when pressing back from A   So to really test this  be sure to back out of the browser before starting the application

User · Answer

For this  I use FLAG ACTIVITY CLEAR TOP flag for starting Intent without FLAG ACTIVITY NEW TASK    and launchMode    singleTask  in manifest for launched activity   Seems like it works as I need - activity does not restart and all other activities are closed

User · Answer

I have started Activity A- B- C- D  When the back button is pressed on Activity D I want to go to Activity A  Since A is my starting point and therefore already on the stack all the activities in top of A is cleared and you can t go back to any other Activity from A    This actually works in my code    Override public boolean onKeyDown int keyCode  KeyEvent event        if  keyCode    KeyEvent KEYCODE BACK            Intent a   new Intent this A class           a addFlags Intent FLAG ACTIVITY CLEAR TOP           startActivity a           return true            return super onKeyDown keyCode  event

User · Answer

Initially I also had problem getting FLAG ACTIVITY CLEAR TOP to work  Eventually I got it to work by using the value of it  0x04000000   So looks like there s an Eclipse compiler issue  But unfortunately the surviving activity is restarted  which is not what I want  So looks like there s no easy solution

User · Answer

I use three flags to resolve the problem   intent addFlags Intent FLAG ACTIVITY CLEAR TOP                  Intent FLAG ACTIVITY CLEAR TASK                    Intent FLAG ACTIVITY NEW TASK

User · Answer

bitestar has the correct solution  but there is one more step   It was hidden away in the docs  however you must change the launchMode of the Activity to anything other than standard  Otherwise it will be destroyed and recreated instead of being reset to the top

User · Answer

Add android noHistory  true  in manifest file     lt manifest  gt           lt activity             android name  UI              android noHistory  true   gt    lt  manifest gt

User · Answer

FLAG ACTIVITY NEW TASK is the problem here which initiates a new task  Just remove it  amp  you are done   Well I recommend you to read what every Flag does before working with them  Read this  amp  Intent Flags here

User · Answer

Though this question already has sufficient answers  I thought somebody would want to know why this flag works in this peculiar manner  This is what I found in Android documentation     The currently running instance of activity B in the above example will either receive the new intent you are starting here in its onNewIntent   method  or be itself finished and restarted with the new intent  If it has declared its launch mode to be  multiple   the default  and you have not set FLAG ACTIVITY SINGLE TOP in the same intent  then it will be finished and re-created  for all other launch modes or if FLAG ACTIVITY SINGLE TOP is set then this Intent will be delivered to the current instance s onNewIntent       So  Either   1  Change the launchMode of the Activity A to something else from standard  ie  singleTask or something   Then your flag FLAG ACTIVITY CLEAR TOP will not restart your Activity A   or   2  Use Intent FLAG ACTIVITY CLEAR TOP   Intent FLAG ACTIVITY SINGLE TOP as your flag  Then it will work the way you desire

[java] How do you use Intent.FLAG_ACTIVITY_CLEAR_TOP to clear the Activity Stack?

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