android開發之Parcelable使用詳解

想要在兩個activity之間傳遞對象，那麼這個對象必須序列化，android中序列化一個對象有兩種方式，一種是實現Serializable接口，這個非常簡單，只需要聲明一下就可以了，不痛不癢。但是android中還有一種特有的序列化方法，那就是實現Parcelable接口，使用這種方式來序列化的效率要高於實現Serializable接口。不過Serializable接口實在是太方便了，因此在某些情況下實現這個接口還是非常不錯的選擇。
使用Parcelable步驟：
1.實現Parcelable接口
2.實現接口中的兩個方法

public int describeContents();
public void writeToParcel(Parcel dest, int flags);

第一個方法是內容接口描述，默認返回0就可以了
第二個方法是將我們的對象序列化一個Parcel對象，也就是將我們的對象存入Parcel中
3.實例化靜態內部對象CREATOR實現接口Parcelable.Creator，實例化CREATOR時要實現其中的兩個方法，其中createFromParcel的功能就是從Parcel中讀取我們的對象。

也就是說我們先利用writeToParcel方法寫入對象，再利用createFromParcel方法讀取對象，因此這兩個方法中的讀寫順序必須一致，否則會出現數據紊亂，一會我會舉例子。
看一個代碼示例：

public class Person implements Parcelable{

    private String username;
    private String nickname;
    private int age;
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getNickname() {
        return nickname;
    }
    public void setNickname(String nickname) {
        this.nickname = nickname;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public Person(String username, String nickname, int age) {
        super();
        this.username = username;
        this.nickname = nickname;
        this.age = age;
    }
    public Person() {
        super();
    }
    /**
     * 這裡的讀的順序必須與writeToParcel(Parcel dest, int flags)方法中
     * 寫的順序一致，否則數據會有差錯，比如你的讀取順序如果是：
     * nickname = source.readString();
     * username=source.readString();
     * age = source.readInt();
     * 即調換了username和nickname的讀取順序，那麼你會發現你拿到的username是nickname的數據，
     * 而你拿到的nickname是username的數據
     * @param source
     */
    public Person(Parcel source) {
        username = source.readString();
        nickname=source.readString();
        age = source.readInt();
    }
    /**
     * 這裡默認返回0即可
     */
    @Override
    public int describeContents() {
        return 0;
    }
    /**
     * 把值寫入Parcel中
     */
    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(username);
        dest.writeString(nickname);
        dest.writeInt(age);
    }

    public static final Creator CREATOR = new Creator() {

        /**
         * 供外部類反序列化本類數組使用
         */
        @Override
        public Person[] newArray(int size) {
            return new Person[size];
        }

        /**
         * 從Parcel中讀取數據
         */
        @Override
        public Person createFromParcel(Parcel source) {
            return new Person(source);
        }
    };
}

本工程源碼http://pan.baidu.com/s/1hqzY3go

最後貼上Parcelable源碼，Google已經給了一個示例了：

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the License);
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.os;

/**
 * Interface for classes whose instances can be written to
 * and restored from a {@link Parcel}.  Classes implementing the Parcelable
 * interface must also have a static field called CREATOR, which
 * is an object implementing the {@link Parcelable.Creator Parcelable.Creator}
 * interface.
 * 
 * 

A typical implementation of Parcelable is:

 * public class MyParcelable implements Parcelable {
 *     private int mData;
 *
 *     public int describeContents() {
 *         return 0;
 *     }
 *
 *     public void writeToParcel(Parcel out, int flags) {
 *         out.writeInt(mData);
 *     }
 *
 *     public static final Parcelable.Creator<MyParcelable> CREATOR
 *             = new Parcelable.Creator<MyParcelable>() {
 *         public MyParcelable createFromParcel(Parcel in) {
 *             return new MyParcelable(in);
 *         }
 *
 *         public MyParcelable[] newArray(int size) {
 *             return new MyParcelable[size];
 *         }
 *     };
 *     
 *     private MyParcelable(Parcel in) {
 *         mData = in.readInt();
 *     }
 * }