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 
17 package android.view;
18 
19 import android.os.Parcel;
20 import 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  */
26 public 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      */
AbsSavedState()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      */
AbsSavedState(Parcelable superState)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      */
AbsSavedState(Parcel source)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      */
AbsSavedState(Parcel source, ClassLoader loader)66     protected AbsSavedState(Parcel source, ClassLoader loader) {
67         Parcelable superState = source.readParcelable(loader);
68         mSuperState = superState != null ? superState : EMPTY_STATE;
69     }
70 
getSuperState()71     final public Parcelable getSuperState() {
72         return mSuperState;
73     }
74 
describeContents()75     public int describeContents() {
76         return 0;
77     }
78 
writeToParcel(Parcel dest, int flags)79     public void writeToParcel(Parcel dest, int flags) {
80         dest.writeParcelable(mSuperState, flags);
81     }
82 
83     public static final @android.annotation.NonNull 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