1/*
2 * Copyright (C) 2014 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 */
16package android.animation;
17
18/**
19 * Abstract base class used convert type T to another type V and back again. This
20 * is necessary when the value types of in animation are different from the property
21 * type. BidirectionalTypeConverter is needed when only the final value for the
22 * animation is supplied to animators.
23 * @see PropertyValuesHolder#setConverter(TypeConverter)
24 */
25public abstract class BidirectionalTypeConverter<T, V> extends TypeConverter<T, V> {
26    private BidirectionalTypeConverter mInvertedConverter;
27
28    public BidirectionalTypeConverter(Class<T> fromClass, Class<V> toClass) {
29        super(fromClass, toClass);
30    }
31
32    /**
33     * Does a conversion from the target type back to the source type. The subclass
34     * must implement this when a TypeConverter is used in animations and current
35     * values will need to be read for an animation.
36     * @param value The Object to convert.
37     * @return A value of type T, converted from <code>value</code>.
38     */
39    public abstract T convertBack(V value);
40
41    /**
42     * Returns the inverse of this converter, where the from and to classes are reversed.
43     * The inverted converter uses this convert to call {@link #convertBack(Object)} for
44     * {@link #convert(Object)} calls and {@link #convert(Object)} for
45     * {@link #convertBack(Object)} calls.
46     * @return The inverse of this converter, where the from and to classes are reversed.
47     */
48    public BidirectionalTypeConverter<V, T> invert() {
49        if (mInvertedConverter == null) {
50            mInvertedConverter = new InvertedConverter(this);
51        }
52        return mInvertedConverter;
53    }
54
55    private static class InvertedConverter<From, To> extends BidirectionalTypeConverter<From, To> {
56        private BidirectionalTypeConverter<To, From> mConverter;
57
58        public InvertedConverter(BidirectionalTypeConverter<To, From> converter) {
59            super(converter.getTargetType(), converter.getSourceType());
60            mConverter = converter;
61        }
62
63        @Override
64        public From convertBack(To value) {
65            return mConverter.convert(value);
66        }
67
68        @Override
69        public To convert(From value) {
70            return mConverter.convertBack(value);
71        }
72    }
73}
74