I am on ActivityA, trying to start ActivityB with String input, make some work, and return String output back to ActivityA. I have created Activity Result API helper class, based on this tutorial and ActivityResultContract
(both listed below). I regester for activity result in onCreate() method of ActivityA:
private lateinit var linkLauncher: ActivityResultHandler<String, String?>
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
linkLauncher = ActivityResultHandler(this, extWebLinkAction, GetExtWebLinkContract())
}
The problem is when I call linkLauncher.execute()
method which in turn calles ActivityResultLauncher
's launch() method, both contracts methods get called before ActivityB even launches.
And here is how I am trying to return result from ActivityB to ActiviteA:
setResult(Activity.RESULT_OK, Intent().apply {
putExtra(LINK_TRANSPORT_EXTRA, link)
})
Listing of mentioned classes.
Helper class:
import androidx.activity.ComponentActivity
import androidx.activity.result.ActivityResultCallback
import androidx.activity.result.ActivityResultLauncher
import androidx.activity.result.ActivityResultRegistry
import androidx.activity.result.contract.ActivityResultContract
import androidx.lifecycle.LifecycleOwner
import java.util.*
interface IActivityResult<I> {
fun execute(input: I)
}
class ActivityResultHandler<I, O>(
private val activity: ComponentActivity,
private val func: (O) -> Unit,
private val contract: ActivityResultContract<I, O>
) : IActivityResult<I> by ActivityResultHandlerImpl(
activity.activityResultRegistry,
activity,
func,
contract
) {
private class ActivityResultHandlerImpl<I, O>(
private val registry: ActivityResultRegistry,
private val lifecycleOwner: LifecycleOwner,
private val func: (O) -> Unit,
private val contract: ActivityResultContract<I, O>
): IActivityResult<I> {
private val callback = ActivityResultCallback<O> { output ->
func(output)
}
private var resultLauncher: ActivityResultLauncher<I>
= registry.register(UUID.randomUUID().toString(), lifecycleOwner, contract, callback)
override fun execute(input: I) {
resultLauncher.launch(input)
}
}
}
And here is my ActivityResultContract
:
import android.app.Activity
import android.content.Context
import android.content.Intent
import androidx.activity.result.contract.ActivityResultContract
import com.zultys.mobiledroid.mvvm.ui.chat.group.GroupActivity
import com.zultys.mobiledroid.mvvm.ui.profile.extweb.ExtWebLinkFragment
import com.zultys.mobiledroid.utils.extensions.logd
class GetLinkContract: ActivityResultContract<String, String?>() {
override fun createIntent(context: Context, input: String): Intent =
context.intentFor<ActivityB>
.newTask()
.putExtra(GROUP_ID_EXTRA, groupId)
override fun parseResult(resultCode: Int, intent: Intent?): String? =
when {
resultCode != Activity.RESULT_OK -> null
else -> intent?.getStringExtra(LINK_TRANSPORT_EXTRA)
}
}
The reason why parseResult()
got called right after createIntent()
was .newTask()
flag in createIntent()
method. Also, as ianhanniballake remarked key shouldn't be random.