NotificationChannelBuilder, DSL style android notification channel builder powered by kotlin, simple way to support Android O notification channels

NotificationChannelBuilder.kt

/**
 * @author hglf <a href="https://github.com/hotstu">hglf</a>
 * @since 5/13/19
 * @desc
 */
class Config {
    val chidren: ArrayList<NotificationChannelGroup> = ArrayList()
}
//NOTE: extension properies are resolved static, so here is a little mem leak, call clean() when every thing is done
val extendPenddingChannels = HashMap<NotificationChannelGroup, ArrayList<NotificationChannel>>()

val NotificationChannelGroup.penddingChannels: ArrayList<NotificationChannel>
    get() = if (extendPenddingChannels[this] == null) {
        val value = ArrayList<NotificationChannel>()
        extendPenddingChannels[this] = value
        value
    } else {
        extendPenddingChannels[this]!!
    }

fun config(init: Config.() -> Unit): Config {
    val config = Config()
    config.apply(init)
    return config
}

@RequiresApi(Build.VERSION_CODES.O)
fun Config.applyTo(notificationManager: NotificationManager) {
    notificationManager.createNotificationChannelGroups(chidren)
    notificationManager.createNotificationChannels(chidren.flatMap { it.penddingChannels })
}

fun Config.clean() {
    extendPenddingChannels.clear()
}

@RequiresApi(Build.VERSION_CODES.O)
fun Config.group(
        groupId: String = "default",
        groupName: String = "default",
        init: NotificationChannelGroup.() -> Unit): NotificationChannelGroup {
    val group = NotificationChannelGroup(groupId, groupName)
    chidren.add(group)
    group.apply(init)
    return group
}

@RequiresApi(Build.VERSION_CODES.O)
fun NotificationChannelGroup.channel(
        id: String = "default",
        name: String = "default",
        importance: Int = NotificationManager.IMPORTANCE_DEFAULT,
        init: NotificationChannel.() -> Unit): NotificationChannel {
    val channel = NotificationChannel(id, name, importance)
    channel.group = this.id
    this.penddingChannels.add(channel)
    channel.apply(init)
    return channel
}

usage

/**
 * @author hglf <a href="https://github.com/hotstu">hglf</a>
 * @since 5/14/19
 * @desc
 */
class App : Application() {
    override fun onCreate() {
        super.onCreate()
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
            val config = config {
                group(groupId = "chatGroup", groupName = "chat") {
                    channel(id = "Ch1") {
                        name = "channel1"
                        description = "when some chat request come"
                    }
                    channel(id = "Ch2") {
                        name = "channel2"
                        description = "when some important chat request come"
                        importance = NotificationManager.IMPORTANCE_HIGH
                    }

                }
                group(groupId = "noticeGroup", groupName = "notice") {
                    channel(id = "Ch3") {
                        name = "personal message"
                        description = "send personal message"
                    }
                    channel(id = "Ch4") {
                        name = "broadcast message"
                        description = "send broadcast"
                    }
                }
            }
            config.applyTo(notificationManager)
            config.clean()
        }
    }
}