> You should set the result when your child activity is about to exit - > for example I set the result from my child activity when a button is > clicked and just before exiting it, e.g.: > > // in a button click handler > setResult(...); > finish();
This is the way they do it in the samples, but it makes not much sense - I don't want to have an "exit" or "save" button; users should be able to hit "back" (listening for "back" is my current workaround, but it will probably fail under certain circumstances). > The documentation for Activity mentions that "When an activity exits, > it can call setResult(int) to return data back to its parent." Yes - it says so. But it doesn't say WHEN - this is my problem; I don't know when to setResult efficiently: onPause() doesn't work, onSaveInstanceState() doesn't work; listening for "back" ain't failproof; listening for data changes is ineffective. *sigh* > When you're getting a NPE what does you stacktrace look like? Nevermind the NPE - it comes from RESULT_CANCELLED and Intent.getExtras () returning null. > btw, you shouldn't assume that the parent activity will outlive the > child one - that is, the fact that your parent activity has spawned > another one for result doesn't mean it won't be destroyed should the > system need to destroy it because it's not in the foreground. Yes, I don't. On Mar 4, 1:58 pm, Stoyan Damov <stoyan.da...@gmail.com> wrote: > On Wed, Mar 4, 2009 at 2:41 PM, Chronos <g358279012044...@gmail.com> wrote: > > > Thanks for the idea - but this is not my problem: the result sent is > > the result I set in the onCreate method (a default result); if I fail > > to do this, I will get a java.lang.NullPointerException, which > > underlines my point - setResult() in onPause() is too late; my > > activity is not cancelled either - I always get an Activity.RESULT_OK. > > You should set the result when your child activity is about to exit - > for example I set the result from my child activity when a button is > clicked and just before exiting it, e.g.: > > // in a button click handler > setResult(...); > finish(); > > The documentation for Activity mentions that "When an activity exits, > it can call setResult(int) to return data back to its parent." > > When you're getting a NPE what does you stacktrace look like? > > > > > Do you think, onPause() is the correct point to setResult() ? It seems > > to me, that the result has already been transmitted in some > > communication queue at this point - all calls to setResult() are in > > vain. > > btw, you shouldn't assume that the parent activity will outlive the > child one - that is, the fact that your parent activity has spawned > another one for result doesn't mean it won't be destroyed should the > system need to destroy it because it's not in the foreground. > > > > > On Mar 4, 12:39 pm, Stoyan Damov <stoyan.da...@gmail.com> wrote: > >> Actually read > >> carefullyhttp://developer.android.com/reference/android/app/Activity.html#star...) > > >> On Wed, Mar 4, 2009 at 1:31 PM, Stoyan Damov <stoyan.da...@gmail.com> > >> wrote: > >> > Re: > > >> > - setResult() in client.onPause() is called TOO LATE; the result has > >> > already been transmitted to the parent (although the method > >> > client.onPause() seems to be called in time). > > >> > If the result has been already set, this means that the result value > >> > is CANCELLED immediately after your child activity started. > >> > Read carefully about the launchMode property - > >> >http://developer.android.com/guide/topics/manifest/activity-element.h... > > >> > Cheers > > >> > On Wed, Mar 4, 2009 at 12:59 PM,Chronos<g358279012044...@gmail.com> > >> > wrote: > > >> >> Hello there ;) > > >> >> I have some - maybe simple - problem; unfortunately I cannot find a > >> >> solution: > > >> >> I have two activities which communicate via: startActivityForResult(), > >> >> setResult(), onActivityResult. I will call the first activity "parent" > >> >> and the second one "client", although this may not be technically > >> >> correct; so the order of calls must be: > > >> >> parent.startActivityForResult() > >> >> client.setResult() > >> >> parent.onActivityResult() > > >> >> Now, where should I call setResult in the client activity ? > > >> >> I have already tried various possibilities which have all failed: > > >> >> - setResult() in client.onPause() is called TOO LATE; the result has > >> >> already been transmitted to the parent (although the method > >> >> client.onPause() seems to be called in time). > >> >> - client.onSaveInstanceState() is not guaranteed to be called at all > >> >> (and the documentation hints at the same timing problem). > >> >> - The only TECHNICALLY POSSIBLE solution seems to implement a change- > >> >> listener for any screen element and set the result there. This may > >> >> work in theory, but is NOT VIABLE in practice: (1) it is strenuous and > >> >> error-prone for activities with many elements; (2) it gets even more > >> >> complicated, when side-effects kick in (change one field in dependency > >> >> to another); (3) it is really slow, since one must write ALL contents > >> >> any time, a SINGLE element changes (and the generic Intent > >> >> communication is already slow by design). > > >> >> To me, it would seem most natural to overload the onPause() method and > >> >> setResult() there - once and for all. There MUST be some easier way > >> >> than implementing zounds of listeners ... > > >> >> Am I overlooking something ? Another listener I haven't stumbled over > >> >> yet ? Please prove me wrong ;) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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