TransitionInflater.java revision 8158051cdfef95fc1f22b56bba93b9c610f5ecb1 
1/*
2 * Copyright (C) 2017 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.support.transition;
18
19import android.content.Context;
20import android.content.res.Resources;
21import android.content.res.TypedArray;
22import android.content.res.XmlResourceParser;
23import android.support.annotation.NonNull;
24import android.support.v4.content.res.TypedArrayUtils;
25import android.support.v4.util.ArrayMap;
26import android.util.AttributeSet;
27import android.util.Xml;
28import android.view.InflateException;
29import android.view.ViewGroup;
30
31import org.xmlpull.v1.XmlPullParser;
32import org.xmlpull.v1.XmlPullParserException;
33
34import java.io.IOException;
35import java.lang.reflect.Constructor;
36
37/**
38 * This class inflates scenes and transitions from resource files.
39 */
40public class TransitionInflater {
41
42    private static final Class<?>[] CONSTRUCTOR_SIGNATURE =
43            new Class[]{Context.class, AttributeSet.class};
44    private static final ArrayMap<String, Constructor> CONSTRUCTORS = new ArrayMap<>();
45
46    private final Context mContext;
47
48    private TransitionInflater(@NonNull Context context) {
49        mContext = context;
50    }
51
52    /**
53     * Obtains the TransitionInflater from the given context.
54     */
55    public static TransitionInflater from(Context context) {
56        return new TransitionInflater(context);
57    }
58
59    /**
60     * Loads a {@link Transition} object from a resource
61     *
62     * @param resource The resource id of the transition to load
63     * @return The loaded Transition object
64     * @throws android.content.res.Resources.NotFoundException when the
65     *                                                         transition cannot be loaded
66     */
67    public Transition inflateTransition(int resource) {
68        XmlResourceParser parser = mContext.getResources().getXml(resource);
69        try {
70            return createTransitionFromXml(parser, Xml.asAttributeSet(parser), null);
71        } catch (XmlPullParserException e) {
72            throw new InflateException(e.getMessage(), e);
73        } catch (IOException e) {
74            throw new InflateException(
75                    parser.getPositionDescription() + ": " + e.getMessage(), e);
76        } finally {
77            parser.close();
78        }
79    }
80
81    /**
82     * Loads a {@link TransitionManager} object from a resource
83     *
84     * @param resource The resource id of the transition manager to load
85     * @return The loaded TransitionManager object
86     * @throws android.content.res.Resources.NotFoundException when the
87     *                                                         transition manager cannot be loaded
88     */
89    public TransitionManager inflateTransitionManager(int resource, ViewGroup sceneRoot) {
90        XmlResourceParser parser = mContext.getResources().getXml(resource);
91        try {
92            return createTransitionManagerFromXml(parser, Xml.asAttributeSet(parser), sceneRoot);
93        } catch (XmlPullParserException e) {
94            InflateException ex = new InflateException(e.getMessage());
95            ex.initCause(e);
96            throw ex;
97        } catch (IOException e) {
98            InflateException ex = new InflateException(
99                    parser.getPositionDescription()
100                            + ": " + e.getMessage());
101            ex.initCause(e);
102            throw ex;
103        } finally {
104            parser.close();
105        }
106    }
107
108    //
109    // Transition loading
110    //
111    private Transition createTransitionFromXml(XmlPullParser parser,
112            AttributeSet attrs, Transition parent)
113            throws XmlPullParserException, IOException {
114
115        Transition transition = null;
116
117        // Make sure we are on a start tag.
118        int type;
119        int depth = parser.getDepth();
120
121        TransitionSet transitionSet = (parent instanceof TransitionSet)
122                ? (TransitionSet) parent : null;
123
124        while (((type = parser.next()) != XmlPullParser.END_TAG || parser.getDepth() > depth)
125                && type != XmlPullParser.END_DOCUMENT) {
126
127            if (type != XmlPullParser.START_TAG) {
128                continue;
129            }
130
131            // TODO: Add more Transition types
132            String name = parser.getName();
133            if ("fade".equals(name)) {
134                transition = new Fade(mContext, attrs);
135            } else if ("changeBounds".equals(name)) {
136                transition = new ChangeBounds(mContext, attrs);
137            } else if ("autoTransition".equals(name)) {
138                transition = new AutoTransition(mContext, attrs);
139            } else if ("transitionSet".equals(name)) {
140                transition = new TransitionSet(mContext, attrs);
141            } else if ("transition".equals(name)) {
142                transition = (Transition) createCustom(attrs, Transition.class, "transition");
143            } else if ("targets".equals(name)) {
144                getTargetIds(parser, attrs, parent);
145            } else {
146                throw new RuntimeException("Unknown scene name: " + parser.getName());
147            }
148            if (transition != null) {
149                if (!parser.isEmptyElementTag()) {
150                    createTransitionFromXml(parser, attrs, transition);
151                }
152                if (transitionSet != null) {
153                    transitionSet.addTransition(transition);
154                    transition = null;
155                } else if (parent != null) {
156                    throw new InflateException("Could not add transition to another transition.");
157                }
158            }
159        }
160
161        return transition;
162    }
163
164    private Object createCustom(AttributeSet attrs, Class expectedType, String tag) {
165        String className = attrs.getAttributeValue(null, "class");
166
167        if (className == null) {
168            throw new InflateException(tag + " tag must have a 'class' attribute");
169        }
170
171        try {
172            synchronized (CONSTRUCTORS) {
173                Constructor constructor = CONSTRUCTORS.get(className);
174                if (constructor == null) {
175                    Class<?> c = mContext.getClassLoader().loadClass(className)
176                            .asSubclass(expectedType);
177                    if (c != null) {
178                        constructor = c.getConstructor(CONSTRUCTOR_SIGNATURE);
179                        constructor.setAccessible(true);
180                        CONSTRUCTORS.put(className, constructor);
181                    }
182                }
183                //noinspection ConstantConditions
184                return constructor.newInstance(mContext, attrs);
185            }
186        } catch (Exception e) {
187            throw new InflateException("Could not instantiate " + expectedType + " class "
188                    + className, e);
189        }
190    }
191
192    private void getTargetIds(XmlPullParser parser,
193            AttributeSet attrs, Transition transition) throws XmlPullParserException, IOException {
194
195        // Make sure we are on a start tag.
196        int type;
197        int depth = parser.getDepth();
198
199        while (((type = parser.next()) != XmlPullParser.END_TAG || parser.getDepth() > depth)
200                && type != XmlPullParser.END_DOCUMENT) {
201
202            if (type != XmlPullParser.START_TAG) {
203                continue;
204            }
205
206            String name = parser.getName();
207            if (name.equals("target")) {
208                TypedArray a = mContext.obtainStyledAttributes(attrs, Styleable.TRANSITION_TARGET);
209                int id = TypedArrayUtils.getNamedResourceId(a, parser, "targetId",
210                        Styleable.TransitionTarget.TARGET_ID, 0);
211                String transitionName;
212                if (id != 0) {
213                    transition.addTarget(id);
214                } else if ((id = TypedArrayUtils.getNamedResourceId(a, parser, "excludeId",
215                        Styleable.TransitionTarget.EXCLUDE_ID, 0)) != 0) {
216                    transition.excludeTarget(id, true);
217                } else if ((transitionName = TypedArrayUtils.getNamedString(a, parser, "targetName",
218                        Styleable.TransitionTarget.TARGET_NAME)) != null) {
219                    transition.addTarget(transitionName);
220                } else if ((transitionName = TypedArrayUtils.getNamedString(a, parser,
221                        "excludeName", Styleable.TransitionTarget.EXCLUDE_NAME)) != null) {
222                    transition.excludeTarget(transitionName, true);
223                } else {
224                    String className = TypedArrayUtils.getNamedString(a, parser,
225                            "excludeClass", Styleable.TransitionTarget.EXCLUDE_CLASS);
226                    try {
227                        if (className != null) {
228                            Class clazz = Class.forName(className);
229                            transition.excludeTarget(clazz, true);
230                        } else if ((className = TypedArrayUtils.getNamedString(a, parser,
231                                "targetClass", Styleable.TransitionTarget.TARGET_CLASS)) != null) {
232                            Class clazz = Class.forName(className);
233                            transition.addTarget(clazz);
234                        }
235                    } catch (ClassNotFoundException e) {
236                        a.recycle();
237                        throw new RuntimeException("Could not create " + className, e);
238                    }
239                }
240                a.recycle();
241            } else {
242                throw new RuntimeException("Unknown scene name: " + parser.getName());
243            }
244        }
245    }
246
247    //
248    // TransitionManager loading
249    //
250
251    private TransitionManager createTransitionManagerFromXml(XmlPullParser parser,
252            AttributeSet attrs, ViewGroup sceneRoot) throws XmlPullParserException, IOException {
253
254        // Make sure we are on a start tag.
255        int type;
256        int depth = parser.getDepth();
257        TransitionManager transitionManager = null;
258
259        while (((type = parser.next()) != XmlPullParser.END_TAG || parser.getDepth() > depth)
260                && type != XmlPullParser.END_DOCUMENT) {
261
262            if (type != XmlPullParser.START_TAG) {
263                continue;
264            }
265
266            String name = parser.getName();
267            if (name.equals("transitionManager")) {
268                transitionManager = new TransitionManager();
269            } else if (name.equals("transition") && (transitionManager != null)) {
270                loadTransition(attrs, parser, sceneRoot, transitionManager);
271            } else {
272                throw new RuntimeException("Unknown scene name: " + parser.getName());
273            }
274        }
275        return transitionManager;
276    }
277
278    private void loadTransition(AttributeSet attrs, XmlPullParser parser, ViewGroup sceneRoot,
279            TransitionManager transitionManager) throws Resources.NotFoundException {
280
281        TypedArray a = mContext.obtainStyledAttributes(attrs, Styleable.TRANSITION_MANAGER);
282        int transitionId = TypedArrayUtils.getNamedResourceId(a, parser, "transition",
283                Styleable.TransitionManager.TRANSITION, -1);
284        int fromId = TypedArrayUtils.getNamedResourceId(a, parser, "fromScene",
285                Styleable.TransitionManager.FROM_SCENE, -1);
286        Scene fromScene = (fromId < 0) ? null : Scene.getSceneForLayout(sceneRoot, fromId,
287                mContext);
288        int toId = TypedArrayUtils.getNamedResourceId(a, parser, "toScene",
289                Styleable.TransitionManager.TO_SCENE, -1);
290        Scene toScene = (toId < 0) ? null : Scene.getSceneForLayout(sceneRoot, toId, mContext);
291
292        if (transitionId >= 0) {
293            Transition transition = inflateTransition(transitionId);
294            if (transition != null) {
295                if (toScene == null) {
296                    throw new RuntimeException("No toScene for transition ID " + transitionId);
297                }
298                if (fromScene == null) {
299                    transitionManager.setTransition(toScene, transition);
300                } else {
301                    transitionManager.setTransition(fromScene, toScene, transition);
302                }
303            }
304        }
305        a.recycle();
306    }
307
308}
309