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<Article> articles; public Collection<Article> getArticles() { return articles; } public void setArticles(Collection<Article> 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<Article> articles;
每个User关联一个或多个Article，如果我在User中声明一个Collection<Article> articles，我能否在查询User的时候，一并能够获取到articles的值。
@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<String, Dao> daos = new HashMap<String, Dao>(); 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<User, Integer> 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<Void>() { @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; } }
ArticleDao操作类
public class ArticleDao { private Dao<Article, Integer> 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<Article> listByUserId(int userId) { try { QueryBuilder<Article, Integer> articleBuilder = articleDaoOpe .queryBuilder(); QueryBuilder userBuilder = helper.getDao(User.class).queryBuilder(); articleBuilder.join(userBuilder); /*Where<Article, Integer> 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！
