diff --git a/app/src/main/java/com/hippo/scene/Scene.java b/app/src/main/java/com/hippo/scene/Scene.java
index 043332132..d43a12760 100644
--- a/app/src/main/java/com/hippo/scene/Scene.java
+++ b/app/src/main/java/com/hippo/scene/Scene.java
@@ -105,11 +105,10 @@ public abstract class Scene {
     }
 
     /**
-     * You will get null before onCreate and after onDestroy mostly
-     *
-     * @return Null or nonull
+     * Must call it after onCreate and before onDestroy
      */
-    public @Nullable SceneView getSceneView() {
+    public @NonNull SceneView getSceneView() {
+        AssertUtils.assertNotNull("Must call it after onCreate and before onDestroy", mSceneView);
         return mSceneView;
     }
 
@@ -203,7 +202,7 @@ public abstract class Scene {
     public void setBackgroundColor(int bgColor) {
         if (mBackgroundColor != bgColor) {
             mBackgroundColor = bgColor;
-            View sceneView = getSceneView();
+            View sceneView = mSceneView;
             if (sceneView != null) {
                 sceneView.setBackgroundColor(bgColor);
             }
@@ -284,7 +283,7 @@ public abstract class Scene {
      * @return The view if found or null otherwise.
      */
     public View findViewById(int resId) {
-        View sceneView = getSceneView();
+        View sceneView = mSceneView;
         if (sceneView != null) {
             return sceneView.findViewById(resId);
         } else {
diff --git a/app/src/main/java/com/hippo/scene/SimpleCurtain.java b/app/src/main/java/com/hippo/scene/SimpleCurtain.java
index 98e358cf8..13c6f0b76 100644
--- a/app/src/main/java/com/hippo/scene/SimpleCurtain.java
+++ b/app/src/main/java/com/hippo/scene/SimpleCurtain.java
@@ -24,7 +24,6 @@ import android.view.ViewTreeObserver;
 
 import com.hippo.animation.SimpleAnimatorListener;
 import com.hippo.util.AnimationUtils;
-import com.hippo.util.AssertUtils;
 import com.hippo.util.ViewUtils;
 
 public class SimpleCurtain extends Curtain {
@@ -47,8 +46,6 @@ public class SimpleCurtain extends Curtain {
     @Override
     public void open(@NonNull final Scene enter, @NonNull final Scene exit) {
         final View enterSceneView = enter.getSceneView();
-        AssertUtils.assertNotNull("Enter scene view must not be null.", enterSceneView);
-
         ViewUtils.setVisibility(enterSceneView, View.INVISIBLE);
 
         enterSceneView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@@ -109,8 +106,6 @@ public class SimpleCurtain extends Curtain {
         showSceneOnClose(enter);
 
         final View exitSceneView = exit.getSceneView();
-        AssertUtils.assertNotNull("Exit scene view must not be null.", exitSceneView);
-
         int width = exitSceneView.getWidth();
         int height = exitSceneView.getHeight();
         float translationX = 0f;
diff --git a/app/src/main/java/com/hippo/scene/StageActivity.java b/app/src/main/java/com/hippo/scene/StageActivity.java
index eafb84e22..49ff9de4b 100644
--- a/app/src/main/java/com/hippo/scene/StageActivity.java
+++ b/app/src/main/java/com/hippo/scene/StageActivity.java
@@ -70,16 +70,12 @@ public abstract class StageActivity extends StatsActivity {
 
     void attachSceneToStage(Scene scene) {
         View sceneView = scene.getSceneView();
-        if (sceneView != null) {
-            getStageLayout().addView(sceneView);
-        }
+        getStageLayout().addView(sceneView);
     }
 
     void detachSceneFromStage(Scene scene) {
         View sceneView = scene.getSceneView();
-        if (sceneView != null) {
-            getStageLayout().removeView(sceneView);
-        }
+        getStageLayout().removeView(sceneView);
     }
 
     public void startScene(@NonNull Class sceneClass) {
diff --git a/app/src/main/java/com/hippo/scene/TransitionCurtain.java b/app/src/main/java/com/hippo/scene/TransitionCurtain.java
index 49363612f..be4c9d1ab 100644
--- a/app/src/main/java/com/hippo/scene/TransitionCurtain.java
+++ b/app/src/main/java/com/hippo/scene/TransitionCurtain.java
@@ -29,7 +29,6 @@ import android.widget.AbsoluteLayout;
 
 import com.hippo.animation.ArgbEvaluator;
 import com.hippo.animation.SimpleAnimatorListener;
-import com.hippo.util.AssertUtils;
 import com.hippo.util.Log;
 import com.hippo.util.ViewUtils;
 import com.hippo.widget.GlobalLayoutSet;
@@ -122,8 +121,6 @@ public class TransitionCurtain extends Curtain {
             Set<TransitionItem> transitionItemSet = mTransitionItemSet;
 
             ViewGroup enterSceneView = mEnterScene.getSceneView();
-            AssertUtils.assertNotNull("Enter scene view must not be null.", enterSceneView);
-
             GlobalLayoutSet globalLayoutSet = new GlobalLayoutSet();
 
             for (TransitionItem item : transitionItemSet) {
@@ -214,7 +211,6 @@ public class TransitionCurtain extends Curtain {
                         ViewUtils.setVisibility(item.exitView, View.VISIBLE);
 
                         ViewGroup enterSceneView = mEnterScene.getSceneView();
-                        AssertUtils.assertNotNull("Enter scene view must not be null.", enterSceneView);
                         enterSceneView.removeView(item.bmpView);
 
                         item.bmp.recycle();
@@ -294,8 +290,6 @@ public class TransitionCurtain extends Curtain {
             Set<TransitionItem> transitionItemSet = mTransitionItemSet;
 
             ViewGroup exitSceneView = mExitScene.getSceneView();
-            AssertUtils.assertNotNull("Exit scene view must not be null.", exitSceneView);
-
             GlobalLayoutSet globalLayoutSet = new GlobalLayoutSet();
 
             for (TransitionItem item : transitionItemSet) {
@@ -385,7 +379,6 @@ public class TransitionCurtain extends Curtain {
                         ViewUtils.setVisibility(item.exitView, View.VISIBLE);
 
                         ViewGroup exitSceneView = mExitScene.getSceneView();
-                        AssertUtils.assertNotNull("Exit scene view must not be null.", exitSceneView);
                         exitSceneView.removeView(item.bmpView);
 
                         item.bmp.recycle();