refactor: refactor Scene.getNavigationScene and Scene.requireNavigati…

…onScene, prepare to splite navigation library

library/scene/src/main/java/com/bytedance/scene/Scene.java

@@ -39,6 +39,7 @@
 import androidx.lifecycle.ViewModelStoreOwner;
 
 import com.bytedance.scene.navigation.NavigationScene;
+import com.bytedance.scene.navigation.NavigationSceneGetter;
 import com.bytedance.scene.parcel.ParcelConstants;
 import com.bytedance.scene.utlity.ViewRefUtility;
 import com.bytedance.scene.utlity.SceneInternalException;
@@ -134,7 +135,11 @@ public abstract class Scene implements LifecycleOwner, ViewModelStoreOwner {
     private Scene mParentScene;
     private Scope.RootScopeFactory mRootScopeFactory = Scope.DEFAULT_ROOT_SCOPE_FACTORY;
     private Scope mScope;
-    private NavigationScene mNavigationScene;
+    /**
+     * use NavigationSceneGetter instead
+     */
+    @Deprecated
+    private Object mNavigationScene;
     private State mState = State.NONE;
     private final StringBuilder mStateHistoryBuilder = new StringBuilder(mState.name);
     private Bundle mArguments;
@@ -280,11 +285,6 @@ void rest() {
     public void dispatchAttachScene(@Nullable Scene parentScene) {
         if (parentScene != null) {
             this.mParentScene = parentScene;
-            if (this.mParentScene instanceof NavigationScene) {
-                this.mNavigationScene = (NavigationScene) this.mParentScene;
-            } else {
-                this.mNavigationScene = this.mParentScene.getNavigationScene();
-            }
         }
         mCalled = false;
         onAttach();
@@ -839,23 +839,12 @@ public final Scene requireParentScene() {
 
     @Nullable
     public final NavigationScene getNavigationScene() {
-        return this.mNavigationScene;
+        return NavigationSceneGetter.getNavigationScene(this);
     }
 
     @NonNull
     public final NavigationScene requireNavigationScene() {
-        NavigationScene navigationScene = getNavigationScene();
-        if (navigationScene == null) {
-            Context context = getApplicationContext();
-            if (context == null) {
-                throw new IllegalStateException("Scene " + this + " is not attached to any Scene");
-            } else if (this instanceof NavigationScene) {
-                throw new IllegalStateException("Scene " + this + " is root Scene");
-            } else {
-                throw new IllegalStateException("The root of the Scene hierarchy is not NavigationScene");
-            }
-        }
-        return navigationScene;
+        return NavigationSceneGetter.requireNavigationScene(this);
     }
 
     @MainThread

library/scene/src/main/java/com/bytedance/scene/navigation/NavigationSceneGetter.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2019 ByteDance Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.bytedance.scene.navigation;
+
+import android.content.Context;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.RestrictTo;
+import androidx.lifecycle.*;
+import com.bytedance.scene.Scene;
+import com.bytedance.scene.navigation.NavigationScene;
+import com.bytedance.scene.utlity.ThreadUtility;
+
+import java.util.WeakHashMap;
+
+import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP;
+
+/**
+ * @hide
+ */
+@RestrictTo(LIBRARY_GROUP)
+public class NavigationSceneGetter {
+    @Nullable
+    public static NavigationScene getNavigationScene(@NonNull final Scene scene) {
+        ThreadUtility.checkUIThread();
+        return findNavigationScene(scene);
+    }
+
+    @Nullable
+    private static NavigationScene findNavigationScene(@Nullable Scene scene) {
+        while (scene != null) {
+            Scene parentScene = scene.getParentScene();
+            if (parentScene instanceof NavigationScene) {
+                return (NavigationScene) parentScene;
+            }
+            scene = parentScene;
+        }
+        return null;
+    }
+
+    @NonNull
+    public static NavigationScene requireNavigationScene(@NonNull Scene scene) {
+        ThreadUtility.checkUIThread();
+        NavigationScene navigationScene = getNavigationScene(scene);
+        if (navigationScene == null) {
+            Context context = scene.getApplicationContext();
+            if (context == null) {
+                throw new IllegalStateException("Scene " + scene + " is not attached to any Scene");
+            } else if (scene instanceof NavigationScene) {
+                throw new IllegalStateException("Scene " + scene + " is root Scene");
+            } else {
+                throw new IllegalStateException("The root of the Scene hierarchy is not NavigationScene");
+            }
+        }
+        return navigationScene;
+    }
+}