[Add/#9] LiveData를 위한 Event.kt 생성

app/src/main/java/org/android/go/sopt/util/Event.kt

@@ -0,0 +1,25 @@
+package org.android.go.sopt.util
+
+import androidx.lifecycle.Observer
+
+class Event<T>(private val content: T) {
+
+    private var hasBeenHandled = false
+
+    fun getContentIfNotHandled(): T? {
+        return if (hasBeenHandled) {
+            null
+        } else {
+            hasBeenHandled = true
+            content
+        }
+    }
+}
+
+class EventObserver<T>(private val onEventUnhandledContent: (T) -> Unit) : Observer<Event<T>> {
+    override fun onChanged(event: Event<T>) {
+        event?.getContentIfNotHandled()?.let {
+            onEventUnhandledContent(it)
+        }
+    }
+}