Lambda passed into a DialogFragment doesn't execute after orientation change

Question

I have this code inside onCreate inside an activity:

        week_info.setOnClickListener { v ->
        ChangeWeekDialogFragment.newInstance(weekPagerAdapter.displayedWeek) { week ->
            week_view_pager.currentItem += week.weeksBetween(weekPagerAdapter.displayedWeek)
        }.show(supportFragmentManager, "ChangeWeekDialogFragment")
    }

The lambda passed into the newInstance function executes when a new week is set inside the ChangeWeekDialogFragment.

The problem is that whenever there's an orientation change while the ChangeWeekDialogFragment is shown and then I change the week, it's as if the line inside the lambda expression wasn't called because the ViewPager doesn't change its displayed item. What's strange though, is that the line week_view_pager.currentItem += week.weeksBetween(weekPagerAdapter.displayedWeek) actually gets called when I set a breakpoint on it.

With no orientation change while the ChangeWeekDialogFragment is opened, everything works as you'd expect.

Thank you!

score 1 · Accepted Answer · edited May 19 '21 at 18:07

Since view is detroyed when orientation changed your dialog view is recreated and so lose any listener added to it. You need to add back listener when you activity/fragment container start

override fun onStart()
{
    super.onStart()
    
    val fragment = fragmentManager.findFragmentByTag("tag")
    fragment?.addListener...
}

This is a quick fix but a better implementation is to use targetFragment from Fragment class which serve the purpose to send data back to the caller if it's a fragment. When creating your dialog fill dialog targetFragment with your fragment caller instance, then when you're done with your dialog (when you click ok for example) from your dialog call

targetFragment.onActivityResult(0 , Activity.RESULT_OK, yourData)

then from your fragment call override onActivityResult

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?)
{
    week_view_pager.currentItem += week.weeksBetween(weekPagerAdapter.displayedWeek)
}

Doing this way you don't have to care about state lost/orientation change/etc... everything works as expected and it looks cleaner than checking if your dialog has been restored from onStart method.

You could also require your "target fragment" to implement whatever arbitrary interface you want and just enforce that requirement in `onCreate` / `onAttach` / etc. That being said, the target fragment API is being deprecated and Google is encouraging the use of the "Fragment Result API". For more details, see https://stackoverflow.com/questions/64869501/how-to-replace-settargetfragment-now-that-it-is-deprecated — Brian Yencho, May 19 '21 at 18:10

Lambda passed into a DialogFragment doesn't execute after orientation change

1 Answers1