Android greenDao3.0的开发实战，包括版本升级(二)

左手的ㄟ右手 2022-06-07 11:53 127阅读 0赞

上一篇文章简单记录了[greenDao的导入和使用][greenDao]，这篇文章则主要是记录在开发中使用greenDao，一些管理类的封装，

主要类的结构如下  
![SouthEast][]

其中DaoMaster、DaoSession、TopicHistoryBeanDao（与上文中UserDao是类似的）是用Make project 自动生成的。

主要思路是，数据库和表分开管理，因为我们可能随着开发进行，添加很多表，

### DaoManager(数据库管理类) ###

public class DaoManager {
        private static DaoManager mInstance;
        private DaoMaster mDaoMaster;
        private DaoSession mDaoSession;
        private static final String DBNAME = "look_history_db";
        private DaoManager() {
            //数据库初始化
    
            DBHelper devOpenHelper = new DBHelper(MyApplication.getContext(),DBNAME,null);
            mDaoMaster = new DaoMaster(devOpenHelper.getWritableDatabase());//是使用的哪个devOpenHelper.getWritableDb()/getWritableDatebase
            mDaoSession = mDaoMaster.newSession();
        }
        public DaoMaster getDaoMaster() {
            return mDaoMaster;
        }
    
        public DaoSession getSession() {
            return mDaoSession;
        }
    
        public static DaoManager getInstance() {
            if (mInstance == null) {
                mInstance = new DaoManager();
            }
            return mInstance;
        }
    }

### EntityManager(数据库表的管理类) ###

表管理类

/* * 数据库中表的管理 * TopicHistoryBeanDao 是数据库中的一个表，这里可以添加很多表的获取，便于管理 */
    
    public class EntityManager { 
        private static EntityManager entityManager;
        private TopicHistoryBeanDao historyBeanDao;
    
        public EntityManager() {
            historyBeanDao = DaoManager.getInstance().getSession().getTopicHistoryBeanDao();
        }
    
        /** * 创建单例 * * @return */
        public static EntityManager getInstance() {
            if (entityManager == null) {
                entityManager = new EntityManager();
            }
            return entityManager;
        }
    
        public TopicHistoryBeanDao getHistoryBeanDao() {
            return historyBeanDao;
        }
    }

## HistroyTableManager(表的数据操作管理类) ##

对应的表的增删改查管理类，这里可以按照你需要的功能进行编写。不是必须这样些，只做提示。  
我觉得还是把HistoryTopicBean的字段贴一下，不然可能会看的难受

TopicHistoryBean

HistroyTableManager

public class HistroyTableManager { 
        private static  HistroyTableManager mInstance;
        public TopicHistoryBeanDao historyBeanDao;
    
        private HistroyTableManager(){
            historyBeanDao=EntityManager.getInstance().getHistoryBeanDao();
        }
        /** * @return */
        public static HistroyTableManager getInstance() {
            if (mInstance == null) {
                mInstance = new HistroyTableManager();
            }
            return mInstance;
        }
    
        /** * 插入数据不能插入相同的帖子数据 * * @param bean */
        public void insert(TopicListBean bean) {
            //当数据库中有该数据的时候,
    
            TopicHistoryBean historyBean = TopicHistoryBean.toTopicHistoryBean(bean);
    
            LogUtils.e("要插入的数据为:historyBean==" + historyBean.toString());
    
            //查询指定的作者和主题的历史记录
            List<TopicHistoryBean> list = getTheTopics(bean.getAuthor(), bean.getSubject());
            boolean isHas = false;
            for (int i = 0; i < list.size(); i++) {
                if (list.get(i).equals(historyBean)) {
                    isHas = true;
                }
            }
            //如果有的话,就进行修改数据
            if (isHas) {
                LogUtils.e("当前帖子已经存在,进行修改参数操作");
            } else {
                historyBeanDao.insert(historyBean);
                LogUtils.e("插入数据");
            }
    
    
        }
    
        public void insert(TopicHistoryBean bean) {
    
    
            historyBeanDao.insert(bean);
        }
    
        /** * 删除某一条数据 * * @param bean */
        public void delete(TopicHistoryBean bean) {
            historyBeanDao.delete(bean);
        }
    
        /** * 删除全部数据 */
        public void deleteAll() {
            historyBeanDao.deleteAll();
        }
    
        /** * 查询全部数据 * * @return */
        public List<TopicHistoryBean> getAllHistory() {
            return historyBeanDao.queryBuilder().list();
        }
    
    
        /** * 查询指定的浏览历史是否已经在数据库中 * * @return */
        public List<TopicHistoryBean> getTheTopics(String name, String subject) {
            return historyBeanDao.queryBuilder()
                    .where(TopicHistoryBeanDao.Properties.Author.eq(name), TopicHistoryBeanDao.Properties.Subject.eq(subject))
                    .build()
                    .list();
        }
    
    }

### 版本升级 ###

*  **greenDao3.0的版本升级，基本思路是：**

创建临时表-->删除原表-->创建新表-->复制临时表数据到新表并删除临时表
    并且我们新增加的和修改的字段做好为String类型，避免字段不能为null的情况发生

[数据库到底该怎么升级][Link 1]

*  **MigrationHelper(数据迁移类)**

public class MigrationHelper { 
    
        private static final String CONVERSION_CLASS_NOT_FOUND_EXCEPTION =
                "MIGRATION HELPER - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS";
    
        private static MigrationHelper instance;
    
    
        public  static  MigrationHelper getInstance(){
            if (instance==null){
                instance = new MigrationHelper();
            }
            return  instance;
        }
    
        /** * 数据迁移 * @param db * @param daoClasses */
        public  void  migrate(Database db, Class<? extends AbstractDao<?,?>>... daoClasses ){ 
            generateTempTables(db, daoClasses);
            DaoMaster.dropAllTables(db, true);
            DaoMaster.createAllTables(db, false);
            restoreData(db, daoClasses);
            LogUtils.i("greenDAO", "MigrationHelper---migrate");
        }
    
    
        /** * 生成临时列表 * @param db * @param daoClasses */
        private void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) { 
            for (int i = 0; i < daoClasses.length; i++) {
                DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
                String divider = "";
                String tableName = daoConfig.tablename;
                String tempTableName = daoConfig.tablename.concat("_TEMP");
                ArrayList<String> properties = new ArrayList<>();
    
                StringBuilder createTableStringBuilder = new StringBuilder();
    
                createTableStringBuilder.append("CREATE TABLE ").append(tempTableName).append(" (");
    
                for (int j = 0; j < daoConfig.properties.length; j++) {
                    String columnName = daoConfig.properties[j].columnName;
    
                    if (getColumns(db, tableName).contains(columnName)) {
                        properties.add(columnName);
    
                        String type = null;
    
                        try {
                            type = getTypeByClass(daoConfig.properties[j].type);
                        } catch (Exception exception) {
                        }
    
                        createTableStringBuilder.append(divider).append(columnName).append(" ").append(type);
    
                        if (daoConfig.properties[j].primaryKey) {
                            createTableStringBuilder.append(" PRIMARY KEY");
                        }
    
                        divider = ",";
                    }
                }
                createTableStringBuilder.append(");");
    
                db.execSQL(createTableStringBuilder.toString());
    
                StringBuilder insertTableStringBuilder = new StringBuilder();
    
                insertTableStringBuilder.append("INSERT INTO ").append(tempTableName).append(" (");
                insertTableStringBuilder.append(TextUtils.join(",", properties));
                insertTableStringBuilder.append(") SELECT ");
                insertTableStringBuilder.append(TextUtils.join(",", properties));
                insertTableStringBuilder.append(" FROM ").append(tableName).append(";");
    
                db.execSQL(insertTableStringBuilder.toString());
            }
        }
    
        private void restoreData(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) { 
            for (int i = 0; i < daoClasses.length; i++) {
                DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);
    
                String tableName = daoConfig.tablename;
                String tempTableName = daoConfig.tablename.concat("_TEMP");
                ArrayList<String> properties = new ArrayList();
    
                for (int j = 0; j < daoConfig.properties.length; j++) {
                    String columnName = daoConfig.properties[j].columnName;
                    if (getColumns(db, tempTableName).contains(columnName)) {
                        properties.add(columnName);
                    }
                }
    
                StringBuilder insertTableStringBuilder = new StringBuilder();
                insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
                insertTableStringBuilder.append(TextUtils.join(",", properties));
                insertTableStringBuilder.append(") SELECT ");
                insertTableStringBuilder.append(TextUtils.join(",", properties));
                insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");
    
                StringBuilder dropTableStringBuilder = new StringBuilder();
    
                dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);
    
                db.execSQL(insertTableStringBuilder.toString());
                db.execSQL(dropTableStringBuilder.toString());
            }
        }
    
        private String getTypeByClass(Class<?> type) throws Exception { 
            if (type.equals(String.class)) {
                return "TEXT";
            }
            if (type.equals(Long.class) || type.equals(Integer.class) || type.equals(long.class)) {
                return "INTEGER";
            }
            if (type.equals(Boolean.class)) {
                return "BOOLEAN";
            }
    
            Exception exception =
                    new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));
            throw exception;
        }
    
        private static List<String> getColumns(Database db, String tableName) {
            List<String> columns = new ArrayList<>();
            Cursor cursor = null;
            try {
                cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 1", null);
                if (cursor != null) {
                    columns = new ArrayList<>(Arrays.asList(cursor.getColumnNames()));
                }
            } catch (Exception e) {
                Log.v(tableName, e.getMessage(), e);
                e.printStackTrace();
            } finally {
                if (cursor != null) cursor.close();
            }
            return columns;
        }
    }

*  **DBHelper(自定义Helper类)**

这里进行版本升级时的数据迁移，等操作

public class DBHelper extends DaoMaster.OpenHelper { 
    
    
    
    
    
        public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
            super(context, name, factory);
        }
    
        @Override
        public void onUpgrade(Database db, int oldVersion, int newVersion) {
    
            //需要对版本升级进行处理
            super.onUpgrade(db, oldVersion, newVersion);
            LogUtils.i("version", oldVersion + "---先前和更新之后的版本---" + newVersion);
            if (oldVersion < newVersion) {
                LogUtils.e("version", oldVersion + "---先前和更新之后的版本---" + newVersion);
                MigrationHelper.getInstance().migrate(db, TopicHistoryBeanDao.class);
                //更改过的实体类(新增的不用加) 更新UserDao文件 可以添加多个 XXDao.class 文件
    // MigrationHelper.getInstance().migrate(db, UserDao.class,XXDao.class);
            }
    
        }
    }

*  **添加字段进行编译**
    
    1.在TopicHistoryBean 中添加一个字段String newColum–>Build–>Make Project 编译后自动将该字段添加到构造函数中，并实现set,get方法。

@Entity
    public class TopicHistoryBean { 
        @Id(autoincrement = true)
        private Long id;
        private String tid;
        private String fid;
        private String forumname;
        private String icon;
        private String author;
        private String authorid;
        private String subject;
        private String postdate;
        private String like_count;
        private String replies;
        private String hits;
        private String attach;
        private long savetime;//保存时间
        private String newColum;//新增字段
    
        @Generated(hash = 461609634)
        public TopicHistoryBean(Long id, String tid, String fid, String forumname, String icon, String author, String authorid, String subject, String postdate,
                String like_count, String replies, String hits, String attach, long savetime, String newColum) {
            this.id = id;
            this.tid = tid;
            this.fid = fid;
            this.forumname = forumname;
            this.icon = icon;
            this.author = author;
            this.authorid = authorid;
            this.subject = subject;
            this.postdate = postdate;
            this.like_count = like_count;
            this.replies = replies;
            this.hits = hits;
            this.attach = attach;
            this.savetime = savetime;
            this.newColum = newColum;
        }
        ...
    
         public String getNewColum() {
            return this.newColum;
        }
    
    
        public void setNewColum(String newColum) {
            this.newColum = newColum;
        }
    }

2.将module中build.gradle中的版本号修改为比当前大–>Sync Now–>as 中的绿箭头安装到模拟器或真机中。

greendao {
            schemaVersion 2   //新版本
            daoPackage 'com.*****.db'//这个是生成代码保存的包名
            targetGenDir 'src/main/java'//保存到java代码路径
        }

3.查看日志

如果出现这条日志，说明你的数据表已经升级ok了

10-19 12:11:48.782 7925-7925/? E/version: [ className=com.alpha.alphaapp.db.DBHelper,methodName=onUpgrade,lineNumber=34 ] 1---先前和更新之后的版本---2

打印保存的HistoryTopicBean,很显然，我们新添的字段newColum，已经存在，但是因为前面的数据没有该字段，所以为null

TopicHistoryBean{id=1, tid='3468', fid='9', forumname='夺晶战神界', icon='http://cdn.gdalpha.com/icon/100/100.jpg', author='大表姐', authorid='26', subject='【官网嘉年华】爆裂王者大作战震撼上线，快来开启你的探索之旅！', postdate='1502251719', like_count='17', replies='27', hits='1419', attach='[]', savetime=1508384399, newColum='null'}

以上就是我的greenDao的使用过程，如果大家在使用过程中存在发现，欢迎及时反馈。共同进步。

[Demo下载地址(非本文Demo)][Demo_Demo]

[greenDao]: http://blog.csdn.net/kenway090704/article/details/78288970
[SouthEast]: /images/20220607/b4db7fee568149389c07d1e0181dbcd4.png
[Link 1]: http://blog.csdn.net/huangxiaoguo1/article/details/54574713
[Demo_Demo]: http://download.csdn.net/download/huangxiaoguo1/9738797