IssueTracker

This has been fixed internally and will be available in the Fragment 1.3.0-alpha04 release.

With this change, using a fragment manager, you can now pass a result between two fragments.

If Fragment A needs a result from Fragment B..

A should call setResultListener():

var result : String? = null

@Override
void onCreate() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    setResultListener("requestKey") { key, bundle ->
      result = bundle.getString("bundleKey")

      // Do something with the result..
    }
  }
}

B should call setResult() with the same key as the listener in A

button("Send result button") {
  val result = "result"
  setResult("requestKey", bundleOf("bundleKey" to result))
}

Fragment A will receive the result and execute its callback once it is STARTED.

Hello . I try to setResultListener from fragment A and Fragment B (A to B and back to A) and return result from FragmentDialog C. Use same request key for fragment A and B. On first load screen A - listener work fine, but when i go to screen B and then return on screen A - listener on fragment A dont work anymore.

Fragment A and fragment B set listeners on onViewCreated callback

            val result =
                bundle.getBoolean(RegularPayAgreementDialog.REGULAR_PAY_AGREEMENT_BUNDLE_KEY)
            if (result) {
                viewModel.onAgreementAccepted()
            }
        }

And set result on DialogFragment

 setFragmentResult(
                    REGULAR_PAY_AGREEMENT_REQUEST_KEY,
                    bundleOf(REGULAR_PAY_AGREEMENT_BUNDLE_KEY to true)
                )

The problem is when 2 fragments try setResultListener with one same result key(

As stated in the documentation "You can have only a single listener and result for a given key."

The Fragment result listeners are not stored in the Fragment, it is actually stored in the FragmentManager. So adding another listener, with the same key for two Fragments with the same FragmentManager will overwrite the first listener.

        LifecycleEventObserver observer = new LifecycleEventObserver() {
                if (event == Lifecycle.Event.ON_DESTROY) {
                    lifecycle.removeObserver(this);    // only remove observer when onDestroy
                    mResultListeners.remove(requestKey);
                }
            }
        };
        lifecycle.addObserver(observer);

I think it would be better remove observer right after the callback is fired, sometimes we don't want the observer keep listening. In that way we could wrap the whole task in one block (like coroutine style), more flexible.

Re #9 - you can certainly clear out your FragmentResultListener after you receive a result if that's the behavior you want for your business logic. The clean up mentioned in your comment is only to prevent memory leaks and not for business logic purposes.