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      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      */
     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