浅谈Android数据库CRUD操作的封装与实现（一）

/**
 * 基本DAO接口
 * @author EwinLive
 *
 * @param <T>
 * @param <PK>
 */
public interface EntityDao<T, PK extends Serializable> {
	
	/**
	 * 添加
	 * @param entity
	 */
	void save(final T entity);
	
	/**
	 * 移除记录（指定ID集）
	 * @param ids 可以有多个
	 */
	void remove(final PK... ids);
	
	/**
	 * 更新
	 * @param entity
	 */
	void upDate(final T entity);

	/**
	 * 按ID查询对象
	 * @param id
	 * @return
	 */
	T find(final PK id);

	/**
	 * 分页查询
	 * @param startResult 开始位置
	 * @param maxResult 记录容量
	 * @return
	 */
	List<T> getScroolData(Integer startResult, Integer maxResult);

	/**
	 * 返回记录总数
	 * @return
	 */
	public Long getCount();

}

/**
 * 简单消息DAO
 * SQLite 
 * dbHelper
 * @author EwinLive
 *
 *事务处理示例：
 		SQLiteDatabase sdb = dbHelper.getReadableDatabase();
		sdb.beginTransaction();//开启事务
		try {
			sdb.execSQL("XXXXX");
			sdb.execSQL("YYYYY");
			sdb.setTransactionSuccessful();//设置事务成功标志
		} catch (SQLException e) {
			e.printStackTrace();
		}
		sdb.endTransaction();//提交事务
 */
public class SimpleMessageDao implements EntityDao<SimpleMessage, Integer> {
	/**
	 * 表名
	 */
	public static final String TABLE = "simple_message";
	
	/**
	 * 数据库管理器
	 * 注意：dbHelper.getReadableDatabase()，会先以可读写方式访问数据库，当磁盘空间已满时会切换到只读方式。
	 */
	DataBaseHelper dbHelper;

	public SimpleMessageDao(Context context) {
		super();
		dbHelper = new DataBaseHelper(context);
	}

	@Override
	public void save(SimpleMessage entity) {
		dbHelper.getReadableDatabase().execSQL(
				"insert into "+ TABLE +"(title, content, time, accountId, consumerId) values(?,?,?,?,?)",
				new Object[]{entity.getTitle(),entity.getContent(),entity.getTime(),entity.getAccountId(),entity.getConsumerId()});
	}
	
	@SuppressWarnings("unused")
	@Override
	public void remove(Integer... ids) {
		if(ids.length > 0){
			StringBuffer sb = new StringBuffer();
			for(Integer id : ids){
				sb.append('?').append(',');
			}
			sb.deleteCharAt(sb.length() - 1);
			dbHelper.getReadableDatabase().execSQL(
					"delete from "+ TABLE +" where id in(" + sb + ")", (Object[]) ids);
		}
	}
	
	@Override
	public void upDate(SimpleMessage entity) {
		dbHelper.getReadableDatabase().execSQL(
				"update "+ TABLE +" set title=?, content=?, time=?, accountId=?, consumerId=? where id =?",
				new Object[]{entity.getTitle(),entity.getContent(),entity.getTime(),entity.getAccountId(),entity.getConsumerId(),entity.getId()});
	}

	@Override
	public SimpleMessage find(Integer id) {
		Cursor cursor = dbHelper.getReadableDatabase().rawQuery("select * from " + TABLE + " where id=?", 
				new String[]{String.valueOf(id)});
		
		if(cursor.moveToNext())
			return new SimpleMessage(cursor.getInt(0),cursor.getString(1),cursor.getString(2),cursor.getString(3),cursor.getInt(4),cursor.getInt(5));
		return null;
	}

	@Override
	public List<SimpleMessage> getScroolData(Integer startResult,
			Integer maxResult) {
		
		List<SimpleMessage> messages = new ArrayList<SimpleMessage>(0);
		Cursor cursor = dbHelper.getReadableDatabase().rawQuery("select * from " + TABLE + " limit ?, ?", 
				new String[]{String.valueOf(startResult), String.valueOf(maxResult)});
		
		while(cursor.moveToNext()){
			messages.add(new SimpleMessage(cursor.getInt(0),cursor.getString(1),cursor.getString(2),cursor.getString(3),cursor.getInt(4),cursor.getInt(5)));
		}
			
		return messages;
	}
	
	@Override
	public Long getCount() {
		Cursor cursor = dbHelper.getReadableDatabase().rawQuery("select count(*) from " + TABLE, 
				null);
		
		if(cursor.moveToNext())
			return cursor.getLong(0);
		return 0l;
	}
}

/**
 * 初始化消息列表
 */
public void initMessageListView(){
	ListView list = (ListView) Main.this.findViewById(R.id.message_list);
	
	//列表数据
	List<HashMap<String, String>> messageListData = new ArrayList<HashMap<String, String>>();

	//查询数据
	SimpleMessageDao smDao = new SimpleMessageDao(Main.this);
	List<SimpleMessage> messages = smDao.getScroolData(1, 20);
	
	//添加数据
	HashMap<String, String> message;
	for(SimpleMessage sm : messages){
		message = new HashMap<String, String>();
		message.put("id", String.valueOf(sm.getId()));
		message.put("content", sm.getContent());
		message.put("time", sm.getTime());
		messageListData.add(message);
	}

	//组装适配器
	SimpleAdapter adapter = new SimpleAdapter(
			Main.this,
			messageListData,
			R.layout.message_list_item,//列表条目的布局样式
			new String[]{"id", "content", "time"},//对应HashMap的Key
			new int[]{R.id.message_id, R.id.message_content, R.id.message_time});//对应TextView的id
	list.setAdapter(adapter);
	
	//设置条目监听器
	list.setOnItemClickListener(new OnItemClickListener(){
		@Override
		public void onItemClick(AdapterView<?> parent, View view,
				int position, long id) {
			ListView listView = (ListView) parent;
			@SuppressWarnings("unchecked")
			HashMap<String, String> data = (HashMap<String, String>) listView.getItemAtPosition(position);
			Toast.makeText(Main.this,
					"ID: " + data.get("id") + " \nContent: " + data.get("content") + "\nTime: " + data.get("time"),
					Toast.LENGTH_SHORT).show();
		}
		
	});
}