fix game view (multiple propertyChange triggering when switching between menu/game screen)

core/src/main/java/io/github/com/quillraven/screen/GameScreen.java

@@ -107,6 +107,7 @@ public class GameScreen extends ScreenAdapter {
     @Override
     public void hide() {
         this.engine.removeAllEntities();
+        this.stage.clear();
     }
 
     @Override

core/src/main/java/io/github/com/quillraven/ui/model/ViewModel.java

@@ -2,6 +2,7 @@ package io.github.com.quillraven.ui.model;
 
 import io.github.com.quillraven.GdxGame;
 
+import java.beans.PropertyChangeListener;
 import java.beans.PropertyChangeSupport;
 
 public abstract class ViewModel {
@@ -19,6 +20,12 @@ public abstract class ViewModel {
         );
     }
 
+    public void clearPropertyChanges() {
+        for (PropertyChangeListener listener : this.propertyChangeSupport.getPropertyChangeListeners()) {
+            this.propertyChangeSupport.removePropertyChangeListener(listener);
+        }
+    }
+
     @FunctionalInterface
     public interface OnPropertyChange<T> {
         void onChange(T value);

core/src/main/java/io/github/com/quillraven/ui/view/GameView.java

@@ -22,7 +22,10 @@ public class GameView extends View<GameViewModel> {
 
         this.lifeGroup = findActor("lifeGroup");
         updateLife(viewModel.getLifePoints());
+    }
 
+    @Override
+    protected void setupPropertyChanges() {
         viewModel.onPropertyChange(GameViewModel.LIFE_POINTS, Integer.class, this::updateLife);
         viewModel.onPropertyChange(GameViewModel.PLAYER_DAMAGE, Map.Entry.class, this::showDamage);
     }

core/src/main/java/io/github/com/quillraven/ui/view/View.java

@@ -28,8 +28,21 @@ public abstract class View<T extends ViewModel> extends Table implements EventLi
         setupUI();
     }
 
+    @Override
+    protected void setStage(Stage stage) {
+        super.setStage(stage);
+        if (stage == null) {
+            viewModel.clearPropertyChanges();
+        } else {
+            setupPropertyChanges();
+        }
+    }
+
     protected abstract void setupUI();
 
+    protected void setupPropertyChanges() {
+    }
+
     public void onLeft() {
     }