android序列化(2)Parcelable与Parcel

1.简介

Parcel  ：　　包裹

　　Android采用这个它封装消息数据。这个是通过IBinder通信的消息的载体。需要明确的是Parcel用来存放数据的是内存（RAM），而不是永久性介质（Nand等）。

Parcelable：　可放入包裹的协议接口

　　如果需要封装到包裹中去，就必须实现这一接口，实现了这一接口，该实体就成为“可打包的”了。

2.示例 

import android.content.Intent;
import android.os.Parcel;
import android.os.Parcelable;

import com.e.weixin.R;
import com.e.weixin.contacts.beans.ContactBean;

public class MsgBean implements Parcelable{

    public static final int MSB_TYPE_TXT = 0;
    public static final int MSB_TYPE_TP = 1;
    public static final int MSB_TYPE_XSP = 2;
    public static final int MSB_TYPE_HB = 3;
    public static final int MSB_TYPE_ZZ = 4;
    public static final int MSB_TYPE_SC = 5;
    public static final int MSB_TYPE_WZ = 6;
    public static final int MSB_TYPE_SPLT = 7;
    public static final int MSB_TYPE_MP = 8;
    public static final int MSB_TYPE_YY = 9;


    ContactBean contact;
    public int type ;
    public String title;
    public String content;
    public int icon;
    public int movie_res;




    //==================
    public MsgBean(){

    }

    //下面代码都是as自动生成
    protected MsgBean(Parcel in) {
        //从Parcel中读一个实现了Parcelable接口的自定义的类，需要ClassLoader
        contact = in.readParcelable(ContactBean.class.getClassLoader());
        type = in.readInt();
        title = in.readString();
        content = in.readString();
        icon = in.readInt();
        movie_res = in.readInt();
    }

    public static final Creator<MsgBean> CREATOR = new Creator<MsgBean>() {
        @Override
        public MsgBean createFromParcel(Parcel in) {
            return new MsgBean(in);
        }

        @Override
        public MsgBean[] newArray(int size) {
            return new MsgBean[size];
        }
    };

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeParcelable(contact,flags);//写另一个自定义的类，它也实现了Parcelable接口
        dest.writeInt(type);
        dest.writeString(title);
        dest.writeString(content);
        dest.writeInt(icon);
        dest.writeInt(movie_res);
    }

    public static void test(){

        int sz = -1,position = -1;
        //1,准备一个Parcel,其它数据放入其中
        Parcel parcel = Parcel.obtain();
        sz = parcel.dataSize();
        position = parcel.dataPosition();

        //2,准备要写入的对象，其中包含另一个实现了Parcelable的对象
        ContactBean cb = new ContactBean();
        cb.name = "name";
        cb.sectionCount = 3;
        cb.isSection = true;
        cb.icon = R.drawable.ebf;

        MsgBean mb1 = new MsgBean();
        mb1.type = 1;
        mb1.icon = R.drawable.ebf;
        mb1.content = "content";
        mb1.title = "title";
        mb1.contact = cb;
        mb1.movie_res = R.raw.movie;

        //3,写入
        mb1.writeToParcel(parcel,1);
        sz = parcel.dataSize();
        position = parcel.dataPosition();

        //4,读取
        MsgBean mb2 = MsgBean.CREATOR.createFromParcel(parcel);

        MsgBean mb3 = parcel.readParcelable(MsgBean.class.getClassLoader());

        parcel.writeParcelable(mb1, 0);

        MsgBean mb4 = MsgBean.CREATOR.createFromParcel(parcel);
        MsgBean mb5 = parcel.readParcelable(MsgBean.class.getClassLoader());


        //5,开始序列
        Intent intent = new Intent();
        intent.putExtra("parcelable",mb1);
        intent.putExtra("int",100);

        //6,开始反序列
        //通常是在另一个地方得到上面的Intent
        MsgBean mb6 = intent.getParcelableExtra("parcelable");
        int data = intent.getIntExtra("int",-1);
    }
}