step1

Author: Dominik Liebler

src/main/kotlin/Main.kt

@@ -4,18 +4,46 @@ import javafx.scene.Scene
 import javafx.scene.control.Label
 import javafx.scene.layout.Pane
 import javafx.stage.Stage
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
 
-class MyApp : Application() {
+class MillisElapsedCounter(private val observer: Observer) {
+    fun start() {
+        GlobalScope.launch(Dispatchers.Default) {
+            var millisElapsed = 0
+
+            while (true) {
+                delay(1000)
+                millisElapsed += 1000
+                observer.notify(millisElapsed)
+            }
+        }
+    }
+
+    interface Observer {
+        fun notify(millisElapsed: Int)
+    }
+}
+
+class MyApp : Application(), MillisElapsedCounter.Observer {
     private val button = Label().also { it.text = "waiting for 0s" }
 
     override fun start(primaryStage: Stage?) {
+        MillisElapsedCounter(this).start()
+
         val pane = Pane().also {
             it.children.add(button)
         }
 
-        primaryStage?.scene = Scene(pane,200.0,200.0)
+        primaryStage?.scene = Scene(pane, 200.0, 200.0)
         primaryStage?.show()
     }
+
+    override fun notify(millisElapsed: Int) {
+        button.text = "waiting for ${millisElapsed / 1000}s"
+    }
 }
 
 fun main() {