TransitionInflater.java revision fdfa819aa29e12734eb90101f5f40d2636a5f1ae 
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 ("explode".equals(name)) {
138                transition = new Explode(mContext, attrs);
139            } else if ("changeImageTransform".equals(name)) {
140                transition = new ChangeImageTransform(mContext, attrs);
141            } else if ("changeTransform".equals(name)) {
142                transition = new ChangeTransform(mContext, attrs);
143            } else if ("changeClipBounds".equals(name)) {
144                transition = new ChangeClipBounds(mContext, attrs);
145            } else if ("autoTransition".equals(name)) {
146                transition = new AutoTransition(mContext, attrs);
147            } else if ("transitionSet".equals(name)) {
148                transition = new TransitionSet(mContext, attrs);
149            } else if ("transition".equals(name)) {
150                transition = (Transition) createCustom(attrs, Transition.class, "transition");
151            } else if ("targets".equals(name)) {
152                getTargetIds(parser, attrs, parent);
153            } else {
154                throw new RuntimeException("Unknown scene name: " + parser.getName());
155            }
156            if (transition != null) {
157                if (!parser.isEmptyElementTag()) {
158                    createTransitionFromXml(parser, attrs, transition);
159                }
160                if (transitionSet != null) {
161                    transitionSet.addTransition(transition);
162                    transition = null;
163                } else if (parent != null) {
164                    throw new InflateException("Could not add transition to another transition.");
165                }
166            }
167        }
168
169        return transition;
170    }
171
172    private Object createCustom(AttributeSet attrs, Class expectedType, String tag) {
173        String className = attrs.getAttributeValue(null, "class");
174
175        if (className == null) {
176            throw new InflateException(tag + " tag must have a 'class' attribute");
177        }
178
179        try {
180            synchronized (CONSTRUCTORS) {
181                Constructor constructor = CONSTRUCTORS.get(className);
182                if (constructor == null) {
183                    Class<?> c = mContext.getClassLoader().loadClass(className)
184                            .asSubclass(expectedType);
185                    if (c != null) {
186                        constructor = c.getConstructor(CONSTRUCTOR_SIGNATURE);
187                        constructor.setAccessible(true);
188                        CONSTRUCTORS.put(className, constructor);
189                    }
190                }
191                //noinspection ConstantConditions
192                return constructor.newInstance(mContext, attrs);
193            }
194        } catch (Exception e) {
195            throw new InflateException("Could not instantiate " + expectedType + " class "
196                    + className, e);
197        }
198    }
199
200    private void getTargetIds(XmlPullParser parser,
201            AttributeSet attrs, Transition transition) throws XmlPullParserException, IOException {
202
203        // Make sure we are on a start tag.
204        int type;
205        int depth = parser.getDepth();
206
207        while (((type = parser.next()) != XmlPullParser.END_TAG || parser.getDepth() > depth)
208                && type != XmlPullParser.END_DOCUMENT) {
209
210            if (type != XmlPullParser.START_TAG) {
211                continue;
212            }
213
214            String name = parser.getName();
215            if (name.equals("target")) {
216                TypedArray a = mContext.obtainStyledAttributes(attrs, Styleable.TRANSITION_TARGET);
217                int id = TypedArrayUtils.getNamedResourceId(a, parser, "targetId",
218                        Styleable.TransitionTarget.TARGET_ID, 0);
219                String transitionName;
220                if (id != 0) {
221                    transition.addTarget(id);
222                } else if ((id = TypedArrayUtils.getNamedResourceId(a, parser, "excludeId",
223                        Styleable.TransitionTarget.EXCLUDE_ID, 0)) != 0) {
224                    transition.excludeTarget(id, true);
225                } else if ((transitionName = TypedArrayUtils.getNamedString(a, parser, "targetName",
226                        Styleable.TransitionTarget.TARGET_NAME)) != null) {
227                    transition.addTarget(transitionName);
228                } else if ((transitionName = TypedArrayUtils.getNamedString(a, parser,
229                        "excludeName", Styleable.TransitionTarget.EXCLUDE_NAME)) != null) {
230                    transition.excludeTarget(transitionName, true);
231                } else {
232                    String className = TypedArrayUtils.getNamedString(a, parser,
233                            "excludeClass", Styleable.TransitionTarget.EXCLUDE_CLASS);
234                    try {
235                        if (className != null) {
236                            Class clazz = Class.forName(className);
237                            transition.excludeTarget(clazz, true);
238                        } else if ((className = TypedArrayUtils.getNamedString(a, parser,
239                                "targetClass", Styleable.TransitionTarget.TARGET_CLASS)) != null) {
240                            Class clazz = Class.forName(className);
241                            transition.addTarget(clazz);
242                        }
243                    } catch (ClassNotFoundException e) {
244                        a.recycle();
245                        throw new RuntimeException("Could not create " + className, e);
246                    }
247                }
248                a.recycle();
249            } else {
250                throw new RuntimeException("Unknown scene name: " + parser.getName());
251            }
252        }
253    }
254
255    //
256    // TransitionManager loading
257    //
258
259    private TransitionManager createTransitionManagerFromXml(XmlPullParser parser,
260            AttributeSet attrs, ViewGroup sceneRoot) throws XmlPullParserException, IOException {
261
262        // Make sure we are on a start tag.
263        int type;
264        int depth = parser.getDepth();
265        TransitionManager transitionManager = null;
266
267        while (((type = parser.next()) != XmlPullParser.END_TAG || parser.getDepth() > depth)
268                && type != XmlPullParser.END_DOCUMENT) {
269
270            if (type != XmlPullParser.START_TAG) {
271                continue;
272            }
273
274            String name = parser.getName();
275            if (name.equals("transitionManager")) {
276                transitionManager = new TransitionManager();
277            } else if (name.equals("transition") && (transitionManager != null)) {
278                loadTransition(attrs, parser, sceneRoot, transitionManager);
279            } else {
280                throw new RuntimeException("Unknown scene name: " + parser.getName());
281            }
282        }
283        return transitionManager;
284    }
285
286    private void loadTransition(AttributeSet attrs, XmlPullParser parser, ViewGroup sceneRoot,
287            TransitionManager transitionManager) throws Resources.NotFoundException {
288
289        TypedArray a = mContext.obtainStyledAttributes(attrs, Styleable.TRANSITION_MANAGER);
290        int transitionId = TypedArrayUtils.getNamedResourceId(a, parser, "transition",
291                Styleable.TransitionManager.TRANSITION, -1);
292        int fromId = TypedArrayUtils.getNamedResourceId(a, parser, "fromScene",
293                Styleable.TransitionManager.FROM_SCENE, -1);
294        Scene fromScene = (fromId < 0) ? null : Scene.getSceneForLayout(sceneRoot, fromId,
295                mContext);
296        int toId = TypedArrayUtils.getNamedResourceId(a, parser, "toScene",
297                Styleable.TransitionManager.TO_SCENE, -1);
298        Scene toScene = (toId < 0) ? null : Scene.getSceneForLayout(sceneRoot, toId, mContext);
299
300        if (transitionId >= 0) {
301            Transition transition = inflateTransition(transitionId);
302            if (transition != null) {
303                if (toScene == null) {
304                    throw new RuntimeException("No toScene for transition ID " + transitionId);
305                }
306                if (fromScene == null) {
307                    transitionManager.setTransition(toScene, transition);
308                } else {
309                    transitionManager.setTransition(fromScene, toScene, transition);
310                }
311            }
312        }
313        a.recycle();
314    }
315
316}
317