SingleLiveEvent example

SingleLiveEvent.kt

import androidx.annotation.MainThread
import androidx.lifecycle.LifecycleOwner
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.Observer
import java.util.concurrent.atomic.AtomicBoolean

class SingleLiveEvent<T> : MutableLiveData<T> {

    constructor() : super()
    constructor(initialValue: T) : super(initialValue)

    private val pending = AtomicBoolean(false)

    @MainThread
    override fun observe(owner: LifecycleOwner, observer: Observer<in T>) {
        super.observe(owner, { t ->
            if (pending.compareAndSet(true, false)) {
                observer.onChanged(t)
            }
        })
    }

    @MainThread
    override fun setValue(value: T) {
        pending.set(true)
        super.setValue(value)
    }

}