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 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     */
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, View layout) {
118        mSceneRoot = sceneRoot;
119        mLayout = layout;
120    }
121
122    /**
123     * @deprecated use {@link #Scene(ViewGroup, View)}.
124     */
125    @Deprecated
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     */
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     */
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     */
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     */
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     */
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     */
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     */
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     */
267    boolean isCreatedFromLayoutResource() {
268        return (mLayoutId > 0);
269    }
270}