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Android中Parcelable接口用法

时间:2015-01-27 23:09:47      阅读:326      评论:0      收藏:0      [点我收藏+]

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from:

http://www.cnblogs.com/renqingping/archive/2012/10/25/Parcelable.html

 

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

 1 public interface Parcelable {
 2     public static final int PARCELABLE_WRITE_RETURN_VALUE = 0x0001;
 3     public static final int CONTENTS_FILE_DESCRIPTOR = 0x0001;
 4     public int describeContents();//返回0即可
    //一个是把本对象(实现了Parcelable的对象)的数据写入Parcel中
5 public void writeToParcel(Parcel dest, int flags); 6   /** 7 * Interface that must be implemented and provided as a public CREATOR 8 * field that generates instances of your Parcelable class from a Parcel. 9 */ 10 public interface Creator<T> {//提供一个内部类,供反序列化的时候把Parcel对象转化为对象,即本对象 11 /** 12 * Create a new instance of the Parcelable class, instantiating it 13 * from the given Parcel whose data had previously been written by 14 * {@link Parcelable#writeToParcel Parcelable.writeToParcel()}. 15 * 16 * @param source The Parcel to read the object‘s data from. 17 * @return Returns a new instance of the Parcelable class. 18 */ 19 public T createFromParcel(Parcel source);//读出source中的数据给T(即本对象) 20 21 /** 22 * Create a new array of the Parcelable class. 23 * 24 * @param size Size of the array. 25 * @return Returns an array of the Parcelable class, with every entry 26 * initialized to null. 27 */ 28 public T[] newArray(int size); 29 } 30 public interface ClassLoaderCreator<T> extends Creator<T> { 31 public T createFromParcel(Parcel source, ClassLoader loader); 32 } 33 }

2.序列化的原因

1)永久性保存对象,保存对象的字节序列到本地文件中;

2)通过序列化对象在网络中传递对象;

3)通过序列化在进程间传递对象。

 

3.Parcelable与Serializable的对比

  • Parcelable

  1.android特有;

  2.实现复杂;

  3.比Serializable高效

  4.可以用于进程间通信(IPC),也可用于intent通讯;

  5.不能使用在要将数据存储在磁盘上的情况,因为Parcelable不能很好的保证数据的持续性在外界有变化的情况下。

  6.复杂类型必须实现Parcelable接口。

  • Serializable

  1.java SE实现;

  2.在序列化的时候会产生大量的临时变量,从而引起频繁的GC。

  3.实现简单

 Parcel是公共的内存空间,所以可以存、取数据。由于是内存操作,所以要比Serialize利用外部存储设备来存、取数据要快!

如果要发送对象最简单的方法是: 把要发的数据直接当做对象发送,接收也不用Bundle(这是可以的),因为已经默认创建。

4.public static final一个都不能少,内部对象CREATOR的名称也不能改变,必须全部大写。

简而言之:通过writeToParcel将你的对象映射成Parcel对象,再通过createFromParcel将Parcel对象映射成你的对象。

5.简单例子

 1 public class Person implements Parcelable {
 2     private String name;
 3     private int age;
 4     private static final String TAG = "Person";
 5 
 6     public String getName() {
 7         return name;
 8     }
 9 
10     public void setName(final String name) {
11         this.name = name;
12     }
13 
14     public int getAge() {
15         return age;
16     }
17 
18     public void setAge(final int age) {
19         this.age = age;
20     }
21 
22     public static final Parcelable.Creator<Person> CREATOR = new Creator<Person>() {
23         @Override
24         public Person createFromParcel(final Parcel source) {
25             Log.d(TAG, "createFromParcel");
26             Person mPerson = new Person();
27             mPerson.name = source.readString();
28             mPerson.age = source.readInt();
29             return mPerson;
30         }
31 
32         @Override
33         public Person[] newArray(final int size) {
34             // TODO Auto-generated method stub
35             return new Person[size];
36         }
37     };
38 
39     @Override
40     public int describeContents() {
41         // TODO Auto-generated method stub
42         Log.d(TAG, "describeContents");
43         return 0;
44     }
45 
46     @Override
47     public void writeToParcel(final Parcel dest, final int flags) {
48         // TODO Auto-generated method stub
49         Log.d(TAG, "writeToParcel");
50         dest.writeString(name);
51         dest.writeInt(age);
52     }
53 }

 

6.writeToParcel()写和createFromParcel()读对象的数据们的顺序必须一致;




Android中Parcelable接口用法

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原文地址:http://www.cnblogs.com/lulj/p/4254049.html

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