diff --git a/app/src/main/java/keijumt/devandroid/databinding/SingleLiveEvent.kt b/app/src/main/java/keijumt/devandroid/databinding/SingleLiveEvent.kt
new file mode 100644
index 0000000..1c3598b
--- /dev/null
+++ b/app/src/main/java/keijumt/devandroid/databinding/SingleLiveEvent.kt
@@ -0,0 +1,59 @@
+package keijumt.devandroid.databinding
+
+import android.arch.lifecycle.LifecycleOwner
+import android.arch.lifecycle.MutableLiveData
+import android.arch.lifecycle.Observer
+import android.support.annotation.MainThread
+import android.util.Log
+import java.util.concurrent.atomic.AtomicBoolean
+
+/**
+ * A lifecycle-aware observable that sends only new updates after subscription, used for events like
+ * navigation and Snackbar messages.
+ *
+ *
+ * This avoids a common problem with events: on configuration change (like rotation) an update
+ * can be emitted if the observer is active. This LiveData only calls the observable if there's an
+ * explicit call to setValue() or call().
+ *
+ *
+ * Note that only one observer is going to be notified of changes.
+ */
+class SingleLiveEvent<T> : MutableLiveData<T>() {
+
+    private val mPending = AtomicBoolean(false)
+
+    @MainThread
+    override fun observe(owner: LifecycleOwner, observer: Observer<T>) {
+
+        if (hasActiveObservers()) {
+            Log.w(TAG, "Multiple observers registered but only one will be notified of changes.")
+        }
+
+        // Observe the internal MutableLiveData
+        super.observe(owner, Observer { t ->
+            if (mPending.compareAndSet(true, false)) {
+                observer.onChanged(t)
+            }
+        })
+    }
+
+    @MainThread
+    override fun setValue(t: T?) {
+        mPending.set(true)
+        super.setValue(t)
+    }
+
+    /**
+     * Used for cases where T is Void, to make calls cleaner.
+     */
+    @MainThread
+    fun call() {
+        value = null
+    }
+
+    companion object {
+
+        private val TAG = "SingleLiveEvent"
+    }
+}
\ No newline at end of file