Improve save

app/src/main/java/com/hippo/scene/Scene.java

@@ -15,7 +15,10 @@
 
 package com.hippo.scene;
 
+import android.os.Bundle;
+import android.os.Parcelable;
 import android.support.v4.app.FragmentManager;
+import android.util.SparseArray;
 import android.view.View;
 import android.widget.FrameLayout;
 
@@ -111,6 +114,20 @@ public abstract class Scene {
         finish();
     }
 
+    protected void onSaveInstanceState(Bundle outState) {
+        SparseArray<Parcelable> states = new SparseArray<>();
+        mRootView.saveHierarchyState(states);
+        outState.putSparseParcelableArray(Integer.toHexString(hashCode()), states);
+    }
+
+    protected void onRestoreInstanceState(Bundle savedInstanceState) {
+        SparseArray<Parcelable> savedStates
+                = savedInstanceState.getSparseParcelableArray(Integer.toHexString(hashCode()));
+        if (savedStates != null) {
+            mRootView.restoreHierarchyState(savedStates);
+        }
+    }
+
     /**
      * Return the FragmentManager for interacting with fragments associated
      * with StageActivity.