android中通过SharedPreferences进行对象的存储

我们知道SharedPreferences只能保存简单类型的数据，例 如，String、int等。如果想用SharedPreferences存取更复杂的数据类型（类、图像等），就需要对这些数据进行编码。我们通常会将 复杂类型的数据转换成Base64编码，然后将转换后的数据以字符串的形式保存在 XML文件中。

注：Base 64是apathe的开源jar包（commons-codec-1.4.jar），需要下载点击打开链接

package hhf.save;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.StreamCorruptedException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.codec.binary.Base64;

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
/**
 * SharedPreferences中写入、读取对象操作
 * @author huanghaifeng
 *
 */
public class SaveObjectActivity extends Activity {
    /** Called when the activity is first created. */
 private SharedPreferences mySharedPreferences;
 private List<Map<String,Object>> wordList = new ArrayList<Map<String,Object>>();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mySharedPreferences = getSharedPreferences("new_word", Activity.MODE_WORLD_READABLE);
        
        saveObjectToShared();
        readObjectFromShared();
    }
    /**
     * 将对象保存到SharedPreferences
     */
    private void saveObjectToShared(){
        
        Map<String,Object> map = new HashMap<String, Object>();
        map.put("name", "张三");
        map.put("age", "19");
        wordList.add(map);
         
        map = new HashMap<String, Object>();
        map.put("name", "李四");
        map.put("age", "29");
        wordList.add(map);
        
         ByteArrayOutputStream baos = new ByteArrayOutputStream(3000);
         ObjectOutputStream oos=null;
         try {
          oos = new ObjectOutputStream(baos);
          oos.writeObject(wordList);
         } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
         }
         // 将Product对象放到OutputStream中
         // 将Product对象转换成byte数组，并将其进行base64编码
         String newWord = new String(Base64.encodeBase64(baos.toByteArray()));
         SharedPreferences.Editor editor = mySharedPreferences.edit();
         // 将编码后的字符串写到base64.xml文件中
         editor.putString("newWord", newWord);
         editor.commit();
    }
    /**
     * 从SharedPreferences中读取对象
     */
   private void readObjectFromShared(){
    String wordBase64 = mySharedPreferences.getString("newWord", "");
    // 对Base64格式的字符串进行解码
        byte[] base64Bytes = Base64.decodeBase64(wordBase64 .getBytes());
          ByteArrayInputStream bais = new ByteArrayInputStream(base64Bytes);
       ObjectInputStream ois;
  try {
   ois = new ObjectInputStream(bais);
    // 从ObjectInputStream中读取Product对象
//   AddNewWord addWord= (AddNewWord ) ois.readObject();
   List<Map<String,Object>> result = (List<Map<String, Object>>) ois.readObject();
   System.out.println("result = " + result);
  } catch (StreamCorruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (ClassNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  
   }
}