PermissionFlow

PermissionFlow.kt

import android.content.Context
import android.content.pm.PackageManager
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
import androidx.lifecycle.LifecycleOwner
import androidx.lifecycle.ProcessLifecycleOwner
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.channels.awaitClose
import kotlinx.coroutines.channels.trySendBlocking
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.callbackFlow
import kotlinx.coroutines.flow.distinctUntilChanged
import kotlinx.coroutines.flow.filter
import kotlinx.coroutines.flow.flowOn
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.onStart

fun permissionFlow(
    context: Context,
    permission: String
): Flow<Boolean> {

    fun hasPermission() = context.checkSelfPermission(permission) == PackageManager.PERMISSION_GRANTED

    return ProcessLifecycleOwner.get().lifecycleEventFlow()
        .filter { it == Lifecycle.Event.ON_RESUME }
        .map { hasPermission() }
        .onStart { emit(hasPermission()) }
        .distinctUntilChanged()
}

private fun LifecycleOwner.lifecycleEventFlow(): Flow<Lifecycle.Event> {
    return callbackFlow {
        val observer = LifecycleEventObserver { _, event -> trySendBlocking(event) }
        lifecycle.addObserver(observer)
        awaitClose { lifecycle.removeObserver(observer) }
    }.flowOn(Dispatchers.Main)
}