Android 用Intent 传递对象之 Parcel

Android 为对象序列化开发了 Parcelable 接口，这个接口要比之前说的 Serializable 更为高效。使用会稍微复杂些。

其主要思想就是把 对象需要保存的数据 放在 parcel 对象中，然后再从 parcel 中恢复这个对象。可见实现 Parcelable这个接口的类，至少会实现两个方法一个用来 将数据保存进 parcel 对象，一个 方法用来从 parcel 中恢复对象。

示例结构：

 先写一个实现了 Parcelable 接口的类 Person，可见 writeToParcel 用来向Parcel 对象写入要保存的对象，

CREATOR 用来恢复对象。存入的数据要和读取的数据顺序对应。

package com.serializabletest;

import android.os.Parcel;
import android.os.Parcelable;
import android.util.Log;

class Person implements Parcelable {

  private static final String TAG = "Person";
  int ID;
  String Name;
  int age;

  public Person(int ID, String Name, int age) {
    this.ID = ID;
    this.Name = Name;
    this.age = age;
  }

  public void printPerson() {
    Log.d(TAG, "ID:" + ID);
    Log.d(TAG, "Name:" + Name);
    Log.d(TAG, "age:" + age);
  }

  // -------------------------------------------------
  public Person(Parcel in) {
    this.ID = in.readInt();
    this.Name = in.readString();
    this.age = in.readInt();
  }

  // 从 Parcel 对象 中恢复 Person 对象
  <span style="color:#ff0000;"><strong>public static final Parcelable.Creator<Person> CREATOR</strong> </span>= new Parcelable.Creator<Person>() {

    @Override
    public Person createFromParcel(Parcel arg0) {
      // TODO Auto-generated method stub
      return new Person(arg0);
    }

    @Override
    public Person[] newArray(int size) {
      // TODO Auto-generated method stub
      return new Person[size];
    }
  };

  /**
   * Describe the kinds of special objects contained in this Parcelable's
   * marshalled(排列) representation(表现).
   * 
   * 用来描述序列化对象中特殊对象的分布状况。
   * 
   * Returns a bitmask indicating the set of special object types marshalled
   * by the Parcelable.
   * 
   * @see android.os.Parcelable#describeContents()
   */

  @Override
  public int describeContents() {
    // TODO Auto-generated method stub
    return 0;
  }

  /**
   * 用来将对象转换成 parcel 对象
   * 
   * 决定了把什么数据写入 parcel
   * 
   * @see android.os.Parcelable#writeToParcel(android.os.Parcel, int)
   */
  // 把 Person 对象转化为 Parcel 对象存储起来
  @Override
  public void <strong><span style="color:#ff0000;">writeToParcel</span></strong>(Parcel arg0, int arg1) {
    // TODO Auto-generated method stub

    arg0.writeInt(ID);
    arg0.writeString(Name);
    arg0.writeInt(age);
  }
}      

MainActivity.java

package com.serializabletest;

import java.io.IOException;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;

public class MainActivity extends Activity {

  public static final String TAG = "MainActivity";
  /** 序列化测试
   * @see android.app.Activity#onCreate(android.os.Bundle)
   */
  private final String objName = "/mnt/sdcard/object.txt";

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setTitle("Intent 传递对象");
    setContentView(R.layout.activity_main);

  }

  public void onBtnClick(View view) throws IOException {
    Person person = new Person(1, "张三", 26);

    Bundle bundle = new Bundle();
    bundle.putParcelable("person", person);
    Intent intent = new Intent(MainActivity.this, SecondActivity.class);
    intent.putExtras(bundle);
    startActivity(intent);
  }
}      

SecondActivity.java

package com.serializabletest;

import java.io.IOException;
import java.io.StreamCorruptedException;

import android.os.Bundle;
import android.view.View;
import android.app.Activity;
import android.content.Intent;

public class SecondActivity extends Activity {

  public static final String TAG = "MainActivity";
  /** 序列化测试
   * @see android.app.Activity#onCreate(android.os.Bundle)
   */
  private final String objName = "/mnt/sdcard/object.txt";

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setTitle("Intent 传递对象");
    setContentView(R.layout.activity_second);

    Intent intent = getIntent();
    Bundle bundle = intent.getExtras();
    Person person = bundle.getParcelable("person");
    person.printPerson();
  }

  public void onBtnClick(View view) throws StreamCorruptedException,
      IOException, ClassNotFoundException {
    this.finish();
  }

}