One-time event wrapper for LiveData

Event.kt

package com.rrtv.utils

/**
 * Used as a wrapper for data that is exposed via a LiveData that represents an event.
 */
open class Event<out T>(private val content: T) {

    var hasBeenHandled = false
        private set

    /**
     * Returns the content and prevents its use again.
     */
    fun getContentIfNotHandled(): T? {
        return if (hasBeenHandled) null else {
            hasBeenHandled = true
            content
        }
    }

    /**
     * Returns the content, even if it's already been handled.
     */
    fun peekContent(): T = content

}

Usage:

class SomeViewModel constructor(private val repository: Repository) {

        val message: MutableLiveData<Event<String>> = MutableLiveData()

        fun someMethod(){
        // do net request
        message.value = Event("Your hint message here")
    }

}

And observe message in your view:

        vm.message.observe(this, Observer { data ->
            data.getContentIfNotHandled()?.let {
                // show your message
            }
        })