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
17package android.transition;
18
19import android.content.Context;
20import android.util.SparseArray;
21import android.view.LayoutInflater;
22import android.view.View;
23import 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 */
32public final class Scene {
33
34    private Context mContext;
35    private int mLayoutId = -1;
36    private ViewGroup mSceneRoot;
37    private ViewGroup 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     */
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     */
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     */
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     */
117    public Scene(ViewGroup sceneRoot, ViewGroup layout) {
118        mSceneRoot = sceneRoot;
119        mLayout = layout;
120    }
121
122    /**
123     * Gets the root of the scene, which is the root of the view hierarchy
124     * affected by changes due to this scene, and which will be animated
125     * when this scene is entered.
126     *
127     * @return The root of the view hierarchy affected by this scene.
128     */
129    public ViewGroup getSceneRoot() {
130        return mSceneRoot;
131    }
132
133    /**
134     * Exits this scene, if it is the current scene
135     * on the scene's {@link #getSceneRoot() scene root}. The current scene is
136     * set when {@link #enter() entering} a scene.
137     * Exiting a scene runs the {@link #setExitAction(Runnable) exit action}
138     * if there is one.
139     */
140    public void exit() {
141        if (getCurrentScene(mSceneRoot) == this) {
142            if (mExitAction != null) {
143                mExitAction.run();
144            }
145        }
146    }
147
148    /**
149     * Enters this scene, which entails changing all values that
150     * are specified by this scene. These may be values associated
151     * with a layout view group or layout resource file which will
152     * now be added to the scene root, or it may be values changed by
153     * an {@link #setEnterAction(Runnable)} enter action}, or a
154     * combination of the these. No transition will be run when the
155     * scene is entered. To get transition behavior in scene changes,
156     * use one of the methods in {@link TransitionManager} instead.
157     */
158    public void enter() {
159
160        // Apply layout change, if any
161        if (mLayoutId > 0 || mLayout != null) {
162            // empty out parent container before adding to it
163            getSceneRoot().removeAllViews();
164
165            if (mLayoutId > 0) {
166                LayoutInflater.from(mContext).inflate(mLayoutId, mSceneRoot);
167            } else {
168                mSceneRoot.addView(mLayout);
169            }
170        }
171
172        // Notify next scene that it is entering. Subclasses may override to configure scene.
173        if (mEnterAction != null) {
174            mEnterAction.run();
175        }
176
177        setCurrentScene(mSceneRoot, this);
178    }
179
180    /**
181     * Set the scene that the given view is in. The current scene is set only
182     * on the root view of a scene, not for every view in that hierarchy. This
183     * information is used by Scene to determine whether there is a previous
184     * scene which should be exited before the new scene is entered.
185     *
186     * @param view The view on which the current scene is being set
187     */
188    static void setCurrentScene(View view, Scene scene) {
189        view.setTagInternal(com.android.internal.R.id.current_scene, scene);
190    }
191
192    /**
193     * Gets the current {@link Scene} set on the given view. A scene is set on a view
194     * only if that view is the scene root.
195     *
196     * @return The current Scene set on this view. A value of null indicates that
197     * no Scene is currently set.
198     */
199    static Scene getCurrentScene(View view) {
200        return (Scene) view.getTag(com.android.internal.R.id.current_scene);
201    }
202
203    /**
204     * Scenes that are not defined with layout resources or
205     * hierarchies, or which need to perform additional steps
206     * after those hierarchies are changed to, should set an enter
207     * action, and possibly an exit action as well. An enter action
208     * will cause Scene to call back into application code to do
209     * anything else the application needs after transitions have
210     * captured pre-change values and after any other scene changes
211     * have been applied, such as the layout (if any) being added to
212     * the view hierarchy. After this method is called, Transitions will
213     * be played.
214     *
215     * @param action The runnable whose {@link Runnable#run() run()} method will
216     * be called when this scene is entered
217     * @see #setExitAction(Runnable)
218     * @see Scene#Scene(ViewGroup, int, Context)
219     * @see Scene#Scene(ViewGroup, ViewGroup)
220     */
221    public void setEnterAction(Runnable action) {
222        mEnterAction = action;
223    }
224
225    /**
226     * Scenes that are not defined with layout resources or
227     * hierarchies, or which need to perform additional steps
228     * after those hierarchies are changed to, should set an enter
229     * action, and possibly an exit action as well. An exit action
230     * will cause Scene to call back into application code to do
231     * anything the application needs to do after applicable transitions have
232     * captured pre-change values, but before any other scene changes
233     * have been applied, such as the new layout (if any) being added to
234     * the view hierarchy. After this method is called, the next scene
235     * will be entered, including a call to {@link #setEnterAction(Runnable)}
236     * if an enter action is set.
237     *
238     * @see #setEnterAction(Runnable)
239     * @see Scene#Scene(ViewGroup, int, Context)
240     * @see Scene#Scene(ViewGroup, ViewGroup)
241     */
242    public void setExitAction(Runnable action) {
243        mExitAction = action;
244    }
245
246
247    /**
248     * Returns whether this Scene was created by a layout resource file, determined
249     * by the layoutId passed into
250     * {@link #getSceneForLayout(android.view.ViewGroup, int, android.content.Context)}.
251     * This is called by TransitionManager to determine whether it is safe for views from
252     * this scene to be removed from their parents when the scene is exited, which is
253     * used by {@link Fade} to fade these views out (the views must be removed from
254     * their parent in order to add them to the overlay for fading purposes). If a
255     * Scene is not based on a resource file, then the impact of removing views
256     * arbitrarily is unknown and should be avoided.
257     */
258    boolean isCreatedFromLayoutResource() {
259        return (mLayoutId > 0);
260    }
261}