Android数据库框架-----ORMLite关联表的使用
上一篇已经对ORMLite框架做了简单的介绍：Android数据库框架-----ORMLite 的基本用法~~本篇将介绍项目可能会使用到的一些用法，也为我们的使用ORMLite框架总结出一个较合理的用法。
本文主要介绍两表相互关联的使用，如同外键，相互的查询功能；
创建 User和Article类
@DatabaseTable(tableName = "tb_user")
public class User
{
@DatabaseField(generatedId = true)
private int id;
@DatabaseField(columnName = "name")
private String name;
@ForeignCollectionField
private Collection articles;
public Collection getArticles()
{
return articles;
}
public void setArticles(Collection articles)
{
this.articles = articles;
}
public User()
{
}
public int getId()
{
return id;
}
public void setId(int id)
{
this.id = id;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
@Override
public String toString()
{
return "User [id=" + id + ", name=" + name + ", articles=" + articles
+ "]";
}
} @ForeignCollectionField
private Collection articles; @DatabaseTable(tableName = "tb_article")
public class Article
{
@DatabaseField(generatedId = true)
private int id;
@DatabaseField
private String title;
@DatabaseField(canBeNull = true, foreign = true, columnName = "user_id", foreignAutoRefresh = true)
private User user;
public int getId()
{
return id;
}
public void setId(int id)
{
this.id = id;
}
public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title = title;
}
public User getUser()
{
return user;
}
public void setUser(User user)
{
this.user = user;
}
@Override
public String toString()
{
return "Article [id=" + id + ", title=" + title + ", user=" + user
+ "]";
}
}在user属性的注解上：@DatabaseField(canBeNull = true, foreign = true, columnName = "user_id", foreignAutoRefresh = true)
添加foreignAutoRefresh =true，这样；当调用queryForId时，拿到Article对象则直接携带了user；
DatabaseHelpe.java
public class DatabaseHelper extends OrmLiteSqliteOpenHelper
{
private static final String TABLE_NAME = "sqlite-test.db";
private Map daos = new HashMap();
private DatabaseHelper(Context context)
{
super(context, TABLE_NAME, null, 4);
}
@Override
public void onCreate(SQLiteDatabase database,
ConnectionSource connectionSource)
{
try
{
TableUtils.createTable(connectionSource, User.class);
TableUtils.createTable(connectionSource, Article.class);
} catch (SQLException e)
{
e.printStackTrace();
}
}
@Override
public void onUpgrade(SQLiteDatabase database,
ConnectionSource connectionSource, int oldVersion, int newVersion)
{
try
{
TableUtils.dropTable(connectionSource, User.class, true);
TableUtils.dropTable(connectionSource, Article.class, true);
onCreate(database, connectionSource);
} catch (SQLException e)
{
e.printStackTrace();
}
}
private static DatabaseHelper instance;
/**
* 单例获取该Helper
*
* @param context
* @return
*/
public static synchronized DatabaseHelper getHelper(Context context)
{
context = context.getApplicationContext();
if (instance == null)
{
synchronized (DatabaseHelper.class)
{
if (instance == null)
instance = new DatabaseHelper(context);
}
}
return instance;
}
public synchronized Dao getDao(Class clazz) throws SQLException
{
Dao dao = null;
String className = clazz.getSimpleName();
if (daos.containsKey(className))
{
dao = daos.get(className);
}
if (dao == null)
{
dao = super.getDao(clazz);
daos.put(className, dao);
}
return dao;
}
/**
* 释放资源
*/
@Override
public void close()
{
super.close();
for (String key : daos.keySet())
{
Dao dao = daos.get(key);
dao = null;
}
}
} Userdao操作类
public class UserDao
{
private Context context;
private Dao userDaoOpe;
private DatabaseHelper helper;
public UserDao(Context context)
{
this.context = context;
try
{
helper = DatabaseHelper.getHelper(context);
userDaoOpe = helper.getDao(User.class);
} catch (SQLException e)
{
e.printStackTrace();
}
}
/**
* 增加一个用户
*
* @param user
* @throws SQLException
*/
public void add(User user)
{
/*//事务操作
TransactionManager.callInTransaction(helper.getConnectionSource(),
new Callable()
{
@Override
public Void call() throws Exception
{
return null;
}
});*/
try
{
userDaoOpe.create(user);
} catch (SQLException e)
{
e.printStackTrace();
}
}
public User get(int id)
{
try
{
return userDaoOpe.queryForId(id);
} catch (SQLException e)
{
e.printStackTrace();
}
return null;
}
} public class ArticleDao
{
private Dao articleDaoOpe;
private DatabaseHelper helper;
@SuppressWarnings("unchecked")
public ArticleDao(Context context)
{
try
{
helper = DatabaseHelper.getHelper(context);
articleDaoOpe = helper.getDao(Article.class);
} catch (SQLException e)
{
e.printStackTrace();
}
}
/**
* 添加一个Article
*
* @param article
*/
public void add(Article article)
{
try
{
articleDaoOpe.create(article);
} catch (SQLException e)
{
e.printStackTrace();
}
}
/**
* 通过Id得到一个Article
*
* @param id
* @return
*/
@SuppressWarnings("unchecked")
public Article getArticleWithUser(int id)
{
Article article = null;
try
{
article = articleDaoOpe.queryForId(id);
helper.getDao(User.class).refresh(article.getUser());
} catch (SQLException e)
{
e.printStackTrace();
}
return article;
}
/**
* 通过Id得到一篇文章
*
* @param id
* @return
*/
public Article get(int id)
{
Article article = null;
try
{
article = articleDaoOpe.queryForId(id);
} catch (SQLException e)
{
e.printStackTrace();
}
return article;
}
/**
* 通过UserId获取所有的文章
*
* @param userId
* @return
*/
public List listByUserId(int userId)
{
try
{
QueryBuilder articleBuilder = articleDaoOpe
.queryBuilder();
QueryBuilder userBuilder = helper.getDao(User.class).queryBuilder();
articleBuilder.join(userBuilder);
/*Where where = articleBuilder.where();
where.eq("user_id", 1);
where.and();
where.eq("title", "ORMLite数据库");
return where.query();*/
// 或者
/*return articleDaoOpe.queryBuilder().//
where().//
eq("user_id", 1).and().//
eq("title", "ORMLite数据库").query();*/
//复杂的查询
/*where.or(
//
where.and(//
where.eq("user_id", 1), where.eq("name", "xxx")),
where.and(//
where.eq("user_id", 2), where.eq("name", "yyy")));*/
return articleDaoOpe.queryBuilder().where().eq("user_id", userId)
.query();
} catch (SQLException e)
{
e.printStackTrace();
}
return null;
}
} 条件查询QueryBuilder的使用
用于where查询，在ArticleDao类中包含的有。更多的用法，去官方文档查看，源码中提供了文档；
提示：运行测试时，要先添加数据，源码未做错误处理 源码点击下载
不足之处请留言指正！有问题的可以给我留言！谢谢！