non sticky LiveData

LiveEvent.kt

sealed class LiveEvent<T> : LiveData<T>() {
    private var version = 0

    /**
     *  override hashCode and equals,
     *  so-that, [LiveData.removeObserver] still can work
     */
    private inner class ObserverWrapper<T>(
        private val other: Observer<T>
    ) : Observer<T> {
        private val registerVersion = version
        override fun onChanged(t: T) {
            // not "sticky" data
            if (version > registerVersion) {
                other.onChanged(t)
            }
        }

        override fun hashCode() = other.hashCode()
        override fun equals(other: Any?) = this.other == other
    }

    override fun observe(owner: LifecycleOwner, observer: Observer<in T>) {
        super.observe(owner, ObserverWrapper(observer))
    }

    override fun observeForever(observer: Observer<in T>) {
        super.observeForever(ObserverWrapper(observer))
    }

    override fun setValue(value: T) {
        version++
        super.setValue(value)
    }
}

class MutableLiveEvent<T> : LiveEvent<T>() {
    public override fun setValue(value: T) {
        super.setValue(value)
    }

    public override fun postValue(value: T) {
        super.postValue(value)
    }
}