content: /*
   * Copyright (C) 2013 The Android Open Source Project
   *
   * 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 android.transition;
  
  import android.annotation.NonNull;
  import android.annotation.Nullable;
  import android.annotation.UnsupportedAppUsage;
  import android.content.Context;
  import android.os.Build;
  import android.util.SparseArray;
  import android.view.LayoutInflater;
  import android.view.View;
  import android.view.ViewGroup;
  
  /**
   * A scene represents the collection of values that various properties in the
   * View hierarchy will have when the scene is applied. A Scene can be
   * configured to automatically run a Transition when it is applied, which will
   * animate the various property changes that take place during the
   * scene change.
   */
  public final class Scene {
  
      private Context mContext;
      private int mLayoutId = -1;
      private ViewGroup mSceneRoot;
      private View mLayout; // alternative to layoutId
      @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
      Runnable mEnterAction;
      @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
      Runnable mExitAction;
  
      /**
       * Returns a Scene described by the resource file associated with the given
       * <code>layoutId</code> parameter. If such a Scene has already been created for
       * the given <code>sceneRoot</code>, that same Scene will be returned.
       * This caching of layoutId-based scenes enables sharing of common scenes
       * between those created in code and those referenced by {@link TransitionManager}
       * XML resource files.
       *
       * @param sceneRoot The root of the hierarchy in which scene changes
       * and transitions will take place.
       * @param layoutId The id of a standard layout resource file.
       * @param context The context used in the process of inflating
       * the layout resource.
       * @return The scene for the given root and layout id
       */
      public static Scene getSceneForLayout(ViewGroup sceneRoot, int layoutId, Context context) {
          SparseArray<Scene> scenes = (SparseArray<Scene>) sceneRoot.getTag(
                  com.android.internal.R.id.scene_layoutid_cache);
          if (scenes == null) {
              scenes = new SparseArray<Scene>();
              sceneRoot.setTagInternal(com.android.internal.R.id.scene_layoutid_cache, scenes);
          }
          Scene scene = scenes.get(layoutId);
          if (scene != null) {
              return scene;
          } else {
              scene = new Scene(sceneRoot, layoutId, context);
              scenes.put(layoutId, scene);
              return scene;
          }
      }
  
      /**
       * Constructs a Scene with no information about how values will change
       * when this scene is applied. This constructor might be used when
       * a Scene is created with the intention of being dynamically configured,
       * through setting {@link #setEnterAction(Runnable)} and possibly
       * {@link #setExitAction(Runnable)}.
       *
       * @param sceneRoot The root of the hierarchy in which scene changes
       * and transitions will take place.
       */
      public Scene(ViewGroup sceneRoot) {
          mSceneRoot = sceneRoot;
      }
  
      /**
       * Constructs a Scene which, when entered, will remove any
       * children from the sceneRoot container and will inflate and add
       * the hierarchy specified by the layoutId resource file.
       *
       * <p>This method is hidden because layoutId-based scenes should be
       * created by the caching factory method {@link Scene#getCurrentScene(ViewGroup)}.</p>
       *
       * @param sceneRoot The root of the hierarchy in which scene changes
       * and transitions will take place.
       * @param layoutId The id of a resource file that defines the view
       * hierarchy of this scene.
       * @param context The context used in the process of inflating
       * the layout resource.
       */
      private Scene(ViewGroup sceneRoot, int layoutId, Context context) {
          mContext = context;
          mSceneRoot = sceneRoot;
          mLayoutId = layoutId;
      }
  
      /**
       * Constructs a Scene which, when entered, will remove any
       * children from the sceneRoot container and add the layout
       * object as a new child of that container.
       *
       * @param sceneRoot The root of the hierarchy in which scene changes
       * and transitions will take place.
       * @param layout The view hierarchy of this scene, added as a child
       * of sceneRoot when this scene is entered.
       */
      public Scene(ViewGroup sceneRoot, View layout) {
          mSceneRoot = sceneRoot;
          mLayout = layout;
      }
  
      /**
       * @deprecated use {@link #Scene(ViewGroup, View)}.
       */
      @Deprecated
      public Scene(ViewGroup sceneRoot, ViewGroup layout) {
          mSceneRoot = sceneRoot;
          mLayout = layout;
      }
  
      /**
       * Gets the root of the scene, which is the root of the view hierarchy
       * affected by changes due to this scene, and which will be animated
       * when this scene is entered.
       *
       * @return The root of the view hierarchy affected by this scene.
       */
      public ViewGroup getSceneRoot() {
          return mSceneRoot;
      }
  
      /**
       * Exits this scene, if it is the current scene
       * on the scene's {@link #getSceneRoot() scene root}. The current scene is
       * set when {@link #enter() entering} a scene.
       * Exiting a scene runs the {@link #setExitAction(Runnable) exit action}
       * if there is one.
       */
      public void exit() {
          if (getCurrentScene(mSceneRoot) == this) {
              if (mExitAction != null) {
                  mExitAction.run();
              }
          }
      }
  
      /**
       * Enters this scene, which entails changing all values that
       * are specified by this scene. These may be values associated
       * with a layout view group or layout resource file which will
       * now be added to the scene root, or it may be values changed by
       * an {@link #setEnterAction(Runnable)} enter action}, or a
       * combination of the these. No transition will be run when the
       * scene is entered. To get transition behavior in scene changes,
       * use one of the methods in {@link TransitionManager} instead.
       */
      public void enter() {
  
          // Apply layout change, if any
          if (mLayoutId > 0 || mLayout != null) {
              // empty out parent container before adding to it
              getSceneRoot().removeAllViews();
  
              if (mLayoutId > 0) {
                  LayoutInflater.from(mContext).inflate(mLayoutId, mSceneRoot);
              } else {
                  mSceneRoot.addView(mLayout);
              }
          }
  
          // Notify next scene that it is entering. Subclasses may override to configure scene.
          if (mEnterAction != null) {
              mEnterAction.run();
          }
  
          setCurrentScene(mSceneRoot, this);
      }
  
      /**
       * Set the scene that the given ViewGroup is in. The current scene is set only
       * on the root ViewGroup of a scene, not for every view in that hierarchy. This
       * information is used by Scene to determine whether there is a previous
       * scene which should be exited before the new scene is entered.
       *
       * @param sceneRoot The ViewGroup on which the current scene is being set
       */
      @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P)
      static void setCurrentScene(@NonNull ViewGroup sceneRoot, @Nullable Scene scene) {
          sceneRoot.setTagInternal(com.android.internal.R.id.current_scene, scene);
      }
  
      /**
       * Gets the current {@link Scene} set on the given ViewGroup. A scene is set on a ViewGroup
       * only if that ViewGroup is the scene root.
       *
       * @param sceneRoot The ViewGroup on which the current scene will be returned
       * @return The current Scene set on this ViewGroup. A value of null indicates that
       * no Scene is currently set.
       */
      @Nullable
      public static Scene getCurrentScene(@NonNull ViewGroup sceneRoot) {
          return (Scene) sceneRoot.getTag(com.android.internal.R.id.current_scene);
      }
  
      /**
       * Scenes that are not defined with layout resources or
       * hierarchies, or which need to perform additional steps
       * after those hierarchies are changed to, should set an enter
       * action, and possibly an exit action as well. An enter action
       * will cause Scene to call back into application code to do
       * anything else the application needs after transitions have
       * captured pre-change values and after any other scene changes
       * have been applied, such as the layout (if any) being added to
       * the view hierarchy. After this method is called, Transitions will
       * be played.
       *
       * @param action The runnable whose {@link Runnable#run() run()} method will
       * be called when this scene is entered
       * @see #setExitAction(Runnable)
       * @see Scene#Scene(ViewGroup, View)
       */
      public void setEnterAction(Runnable action) {
          mEnterAction = action;
      }
  
      /**
       * Scenes that are not defined with layout resources or
       * hierarchies, or which need to perform additional steps
       * after those hierarchies are changed to, should set an enter
       * action, and possibly an exit action as well. An exit action
       * will cause Scene to call back into application code to do
       * anything the application needs to do after applicable transitions have
       * captured pre-change values, but before any other scene changes
       * have been applied, such as the new layout (if any) being added to
       * the view hierarchy. After this method is called, the next scene
       * will be entered, including a call to {@link #setEnterAction(Runnable)}
       * if an enter action is set.
       *
       * @see #setEnterAction(Runnable)
       * @see Scene#Scene(ViewGroup, View)
       */
      public void setExitAction(Runnable action) {
          mExitAction = action;
      }
  
  
      /**
       * Returns whether this Scene was created by a layout resource file, determined
       * by the layoutId passed into
       * {@link #getSceneForLayout(android.view.ViewGroup, int, android.content.Context)}.
       * This is called by TransitionManager to determine whether it is safe for views from
       * this scene to be removed from their parents when the scene is exited, which is
       * used by {@link Fade} to fade these views out (the views must be removed from
       * their parent in order to add them to the overlay for fading purposes). If a
       * Scene is not based on a resource file, then the impact of removing views
       * arbitrarily is unknown and should be avoided.
       */
      boolean isCreatedFromLayoutResource() {
          return (mLayoutId > 0);
      }
  }
  