1 /*
2  * Copyright (C) 2013 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package android.transition;
18 
19 import android.content.Context;
20 import android.util.SparseArray;
21 import android.view.LayoutInflater;
22 import android.view.View;
23 import android.view.ViewGroup;
24 
25 /**
26  * A scene represents the collection of values that various properties in the
27  * View hierarchy will have when the scene is applied. A Scene can be
28  * configured to automatically run a Transition when it is applied, which will
29  * animate the various property changes that take place during the
30  * scene change.
31  */
32 public final class Scene {
33 
34     private Context mContext;
35     private int mLayoutId = -1;
36     private ViewGroup mSceneRoot;
37     private View mLayout; // alternative to layoutId
38     Runnable mEnterAction, mExitAction;
39 
40     /**
41      * Returns a Scene described by the resource file associated with the given
42      * <code>layoutId</code> parameter. If such a Scene has already been created for
43      * the given <code>sceneRoot</code>, that same Scene will be returned.
44      * This caching of layoutId-based scenes enables sharing of common scenes
45      * between those created in code and those referenced by {@link TransitionManager}
46      * XML resource files.
47      *
48      * @param sceneRoot The root of the hierarchy in which scene changes
49      * and transitions will take place.
50      * @param layoutId The id of a standard layout resource file.
51      * @param context The context used in the process of inflating
52      * the layout resource.
53      * @return The scene for the given root and layout id
54      */
getSceneForLayout(ViewGroup sceneRoot, int layoutId, Context context)55     public static Scene getSceneForLayout(ViewGroup sceneRoot, int layoutId, Context context) {
56         SparseArray<Scene> scenes = (SparseArray<Scene>) sceneRoot.getTag(
57                 com.android.internal.R.id.scene_layoutid_cache);
58         if (scenes == null) {
59             scenes = new SparseArray<Scene>();
60             sceneRoot.setTagInternal(com.android.internal.R.id.scene_layoutid_cache, scenes);
61         }
62         Scene scene = scenes.get(layoutId);
63         if (scene != null) {
64             return scene;
65         } else {
66             scene = new Scene(sceneRoot, layoutId, context);
67             scenes.put(layoutId, scene);
68             return scene;
69         }
70     }
71 
72     /**
73      * Constructs a Scene with no information about how values will change
74      * when this scene is applied. This constructor might be used when
75      * a Scene is created with the intention of being dynamically configured,
76      * through setting {@link #setEnterAction(Runnable)} and possibly
77      * {@link #setExitAction(Runnable)}.
78      *
79      * @param sceneRoot The root of the hierarchy in which scene changes
80      * and transitions will take place.
81      */
Scene(ViewGroup sceneRoot)82     public Scene(ViewGroup sceneRoot) {
83         mSceneRoot = sceneRoot;
84     }
85 
86     /**
87      * Constructs a Scene which, when entered, will remove any
88      * children from the sceneRoot container and will inflate and add
89      * the hierarchy specified by the layoutId resource file.
90      *
91      * <p>This method is hidden because layoutId-based scenes should be
92      * created by the caching factory method {@link Scene#getCurrentScene(View)}.</p>
93      *
94      * @param sceneRoot The root of the hierarchy in which scene changes
95      * and transitions will take place.
96      * @param layoutId The id of a resource file that defines the view
97      * hierarchy of this scene.
98      * @param context The context used in the process of inflating
99      * the layout resource.
100      */
Scene(ViewGroup sceneRoot, int layoutId, Context context)101     private Scene(ViewGroup sceneRoot, int layoutId, Context context) {
102         mContext = context;
103         mSceneRoot = sceneRoot;
104         mLayoutId = layoutId;
105     }
106 
107     /**
108      * Constructs a Scene which, when entered, will remove any
109      * children from the sceneRoot container and add the layout
110      * object as a new child of that container.
111      *
112      * @param sceneRoot The root of the hierarchy in which scene changes
113      * and transitions will take place.
114      * @param layout The view hierarchy of this scene, added as a child
115      * of sceneRoot when this scene is entered.
116      */
Scene(ViewGroup sceneRoot, View layout)117     public Scene(ViewGroup sceneRoot, View layout) {
118         mSceneRoot = sceneRoot;
119         mLayout = layout;
120     }
121 
122     /**
123      * @deprecated use {@link #Scene(ViewGroup, View)}.
124      */
125     @Deprecated
Scene(ViewGroup sceneRoot, ViewGroup layout)126     public Scene(ViewGroup sceneRoot, ViewGroup layout) {
127         mSceneRoot = sceneRoot;
128         mLayout = layout;
129     }
130 
131     /**
132      * Gets the root of the scene, which is the root of the view hierarchy
133      * affected by changes due to this scene, and which will be animated
134      * when this scene is entered.
135      *
136      * @return The root of the view hierarchy affected by this scene.
137      */
getSceneRoot()138     public ViewGroup getSceneRoot() {
139         return mSceneRoot;
140     }
141 
142     /**
143      * Exits this scene, if it is the current scene
144      * on the scene's {@link #getSceneRoot() scene root}. The current scene is
145      * set when {@link #enter() entering} a scene.
146      * Exiting a scene runs the {@link #setExitAction(Runnable) exit action}
147      * if there is one.
148      */
exit()149     public void exit() {
150         if (getCurrentScene(mSceneRoot) == this) {
151             if (mExitAction != null) {
152                 mExitAction.run();
153             }
154         }
155     }
156 
157     /**
158      * Enters this scene, which entails changing all values that
159      * are specified by this scene. These may be values associated
160      * with a layout view group or layout resource file which will
161      * now be added to the scene root, or it may be values changed by
162      * an {@link #setEnterAction(Runnable)} enter action}, or a
163      * combination of the these. No transition will be run when the
164      * scene is entered. To get transition behavior in scene changes,
165      * use one of the methods in {@link TransitionManager} instead.
166      */
enter()167     public void enter() {
168 
169         // Apply layout change, if any
170         if (mLayoutId > 0 || mLayout != null) {
171             // empty out parent container before adding to it
172             getSceneRoot().removeAllViews();
173 
174             if (mLayoutId > 0) {
175                 LayoutInflater.from(mContext).inflate(mLayoutId, mSceneRoot);
176             } else {
177                 mSceneRoot.addView(mLayout);
178             }
179         }
180 
181         // Notify next scene that it is entering. Subclasses may override to configure scene.
182         if (mEnterAction != null) {
183             mEnterAction.run();
184         }
185 
186         setCurrentScene(mSceneRoot, this);
187     }
188 
189     /**
190      * Set the scene that the given view is in. The current scene is set only
191      * on the root view of a scene, not for every view in that hierarchy. This
192      * information is used by Scene to determine whether there is a previous
193      * scene which should be exited before the new scene is entered.
194      *
195      * @param view The view on which the current scene is being set
196      */
setCurrentScene(View view, Scene scene)197     static void setCurrentScene(View view, Scene scene) {
198         view.setTagInternal(com.android.internal.R.id.current_scene, scene);
199     }
200 
201     /**
202      * Gets the current {@link Scene} set on the given view. A scene is set on a view
203      * only if that view is the scene root.
204      *
205      * @return The current Scene set on this view. A value of null indicates that
206      * no Scene is currently set.
207      */
getCurrentScene(View view)208     static Scene getCurrentScene(View view) {
209         return (Scene) view.getTag(com.android.internal.R.id.current_scene);
210     }
211 
212     /**
213      * Scenes that are not defined with layout resources or
214      * hierarchies, or which need to perform additional steps
215      * after those hierarchies are changed to, should set an enter
216      * action, and possibly an exit action as well. An enter action
217      * will cause Scene to call back into application code to do
218      * anything else the application needs after transitions have
219      * captured pre-change values and after any other scene changes
220      * have been applied, such as the layout (if any) being added to
221      * the view hierarchy. After this method is called, Transitions will
222      * be played.
223      *
224      * @param action The runnable whose {@link Runnable#run() run()} method will
225      * be called when this scene is entered
226      * @see #setExitAction(Runnable)
227      * @see Scene#Scene(ViewGroup, int, Context)
228      * @see Scene#Scene(ViewGroup, ViewGroup)
229      */
setEnterAction(Runnable action)230     public void setEnterAction(Runnable action) {
231         mEnterAction = action;
232     }
233 
234     /**
235      * Scenes that are not defined with layout resources or
236      * hierarchies, or which need to perform additional steps
237      * after those hierarchies are changed to, should set an enter
238      * action, and possibly an exit action as well. An exit action
239      * will cause Scene to call back into application code to do
240      * anything the application needs to do after applicable transitions have
241      * captured pre-change values, but before any other scene changes
242      * have been applied, such as the new layout (if any) being added to
243      * the view hierarchy. After this method is called, the next scene
244      * will be entered, including a call to {@link #setEnterAction(Runnable)}
245      * if an enter action is set.
246      *
247      * @see #setEnterAction(Runnable)
248      * @see Scene#Scene(ViewGroup, int, Context)
249      * @see Scene#Scene(ViewGroup, ViewGroup)
250      */
setExitAction(Runnable action)251     public void setExitAction(Runnable action) {
252         mExitAction = action;
253     }
254 
255 
256     /**
257      * Returns whether this Scene was created by a layout resource file, determined
258      * by the layoutId passed into
259      * {@link #getSceneForLayout(android.view.ViewGroup, int, android.content.Context)}.
260      * This is called by TransitionManager to determine whether it is safe for views from
261      * this scene to be removed from their parents when the scene is exited, which is
262      * used by {@link Fade} to fade these views out (the views must be removed from
263      * their parent in order to add them to the overlay for fading purposes). If a
264      * Scene is not based on a resource file, then the impact of removing views
265      * arbitrarily is unknown and should be avoided.
266      */
isCreatedFromLayoutResource()267     boolean isCreatedFromLayoutResource() {
268         return (mLayoutId > 0);
269     }
270 }