Created
May 3, 2020 16:52
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import androidx.lifecycle.Observer | |
/** | |
* 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 // Allow external read but not write | |
/** | |
* 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 | |
} | |
/** | |
* An [Observer] for [Event]s, simplifying the pattern of checking if the [Event]'s content has | |
* already been handled. | |
* | |
* [onEventUnhandledContent] is *only* called if the [Event]'s contents has not been handled. | |
*/ | |
open class EventObserver<T>(private val onEventUnhandledContent: (T) -> Unit) : Observer<Event<T>> { | |
override fun onChanged(event: Event<T>?) { | |
event?.getContentIfNotHandled() | |
?.let { value -> | |
onEventUnhandledContent(value) | |
} | |
} | |
} |
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