1/*
2 * Copyright (C) 2006 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.view;
18
19import android.os.Parcel;
20import android.os.Parcelable;
21
22/**
23 * A {@link Parcelable} implementation that should be used by inheritance
24 * hierarchies to ensure the state of all classes along the chain is saved.
25 */
26public abstract class AbsSavedState implements Parcelable {
27    public static final AbsSavedState EMPTY_STATE = new AbsSavedState() {};
28
29    private final Parcelable mSuperState;
30
31    /**
32     * Constructor used to make the EMPTY_STATE singleton
33     */
34    private AbsSavedState() {
35        mSuperState = null;
36    }
37
38    /**
39     * Constructor called by derived classes when creating their SavedState objects
40     *
41     * @param superState The state of the superclass of this view
42     */
43    protected AbsSavedState(Parcelable superState) {
44        if (superState == null) {
45            throw new IllegalArgumentException("superState must not be null");
46        }
47        mSuperState = superState != EMPTY_STATE ? superState : null;
48    }
49
50    /**
51     * Constructor used when reading from a parcel. Reads the state of the superclass.
52     *
53     * @param source parcel to read from
54     */
55    protected AbsSavedState(Parcel source) {
56        this(source, null);
57    }
58
59    /**
60     * Constructor used when reading from a parcel using a given class loader.
61     * Reads the state of the superclass.
62     *
63     * @param source parcel to read from
64     * @param loader ClassLoader to use for reading
65     */
66    protected AbsSavedState(Parcel source, ClassLoader loader) {
67        Parcelable superState = source.readParcelable(loader);
68        mSuperState = superState != null ? superState : EMPTY_STATE;
69    }
70
71    final public Parcelable getSuperState() {
72        return mSuperState;
73    }
74
75    public int describeContents() {
76        return 0;
77    }
78
79    public void writeToParcel(Parcel dest, int flags) {
80        dest.writeParcelable(mSuperState, flags);
81    }
82
83    public static final Parcelable.Creator<AbsSavedState> CREATOR
84            = new Parcelable.ClassLoaderCreator<AbsSavedState>() {
85
86        @Override
87        public AbsSavedState createFromParcel(Parcel in) {
88            return createFromParcel(in, null);
89        }
90
91        @Override
92        public AbsSavedState createFromParcel(Parcel in, ClassLoader loader) {
93            Parcelable superState = in.readParcelable(loader);
94            if (superState != null) {
95                throw new IllegalStateException("superState must be null");
96            }
97            return EMPTY_STATE;
98        }
99
100        @Override
101        public AbsSavedState[] newArray(int size) {
102            return new AbsSavedState[size];
103        }
104    };
105}
106