1/*
2 * Copyright 2018 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 androidx.customview.view;
18
19import android.os.Parcel;
20import android.os.Parcelable;
21
22import androidx.annotation.NonNull;
23import androidx.annotation.Nullable;
24
25/**
26 * A {@link Parcelable} implementation that should be used by inheritance
27 * hierarchies to ensure the state of all classes along the chain is saved.
28 */
29public abstract class AbsSavedState implements Parcelable {
30    public static final AbsSavedState EMPTY_STATE = new AbsSavedState() {};
31
32    private final Parcelable mSuperState;
33
34    /**
35     * Constructor used to make the EMPTY_STATE singleton
36     */
37    private AbsSavedState() {
38        mSuperState = null;
39    }
40
41    /**
42     * Constructor called by derived classes when creating their SavedState objects
43     *
44     * @param superState The state of the superclass of this view
45     */
46    protected AbsSavedState(@NonNull Parcelable superState) {
47        if (superState == null) {
48            throw new IllegalArgumentException("superState must not be null");
49        }
50        mSuperState = superState != EMPTY_STATE ? superState : null;
51    }
52
53    /**
54     * Constructor used when reading from a parcel. Reads the state of the superclass.
55     *
56     * @param source parcel to read from
57     */
58    protected AbsSavedState(@NonNull Parcel source) {
59        this(source, null);
60    }
61
62    /**
63     * Constructor used when reading from a parcel. Reads the state of the superclass.
64     *
65     * @param source parcel to read from
66     * @param loader ClassLoader to use for reading
67     */
68    protected AbsSavedState(@NonNull Parcel source, @Nullable ClassLoader loader) {
69        Parcelable superState = source.readParcelable(loader);
70        mSuperState = superState != null ? superState : EMPTY_STATE;
71    }
72
73    @Nullable
74    public final Parcelable getSuperState() {
75        return mSuperState;
76    }
77
78    @Override
79    public int describeContents() {
80        return 0;
81    }
82
83    @Override
84    public void writeToParcel(Parcel dest, int flags) {
85        dest.writeParcelable(mSuperState, flags);
86    }
87
88    public static final Creator<AbsSavedState> CREATOR = new ClassLoaderCreator<AbsSavedState>() {
89        @Override
90        public AbsSavedState createFromParcel(Parcel in, ClassLoader loader) {
91            Parcelable superState = in.readParcelable(loader);
92            if (superState != null) {
93                throw new IllegalStateException("superState must be null");
94            }
95            return EMPTY_STATE;
96        }
97
98        @Override
99        public AbsSavedState createFromParcel(Parcel in) {
100            return createFromParcel(in, null);
101        }
102
103        @Override
104        public AbsSavedState[] newArray(int size) {
105            return new AbsSavedState[size];
106        }
107    };
108}
109