Android数据库升级，数据迁移

偏执的太偏执、 2024-02-18 21:39 180阅读 0赞

版本迭代时难免需要对数据库字段进行增加，删除与修改操作。这时便需要对原有的数据进行迁移，以保证不丢失数据。对数据库的迁移我们需要做一下几个步骤：

*  ① 创建临时表，将原来的数据复制到临时表中。
 *  ② 删除原表，原表数据已经备份至临时表中，不再需要，进行删除。
 *  ③ 创建新表，调用创建新表的方法，创建所有的新表。
 *  ④ 恢复原表的数据，将临时表中的数据恢复至新表中。
 *  ⑤ 删除临时表，完成所有的步骤。

具体步骤：

1.引入GreenDaoUpgradeHelper

compile 'com.github.yuweiguocn:GreenDaoUpgradeHelper:v2.0.2'

2.在新建DaoManager类

public class DaoManager \{

private DaoMaster mDaoMaster;

private DaoSession mDaoSession;

private static volatile DaoManager mInstance = null;

public static final String DATABASE\_NAME = "greendao";

private DaoManager(Context context) \{

MySQLiteOpenHelper helper = new MySQLiteOpenHelper(context, DATABASE\_NAME, null);

mDaoMaster = new DaoMaster(helper.getWritableDatabase());

/\* AppOpenHelper helper = new AppOpenHelper(CCApplication.getInstance().getApplicationContext(), DATABASE\_NAME);

Database db = helper.getWritableDb();

mDaoMaster = new DaoMaster(db);\*/

mDaoSession = mDaoMaster.newSession();

public static DaoManager getInstance(Context context) \{

if (mInstance == null) \{

synchronized (DaoManager.class) \{

if (mInstance == null) \{

mInstance = new DaoManager(context);

return mInstance;

public DaoMaster getMaster() \{

return mDaoMaster;

public DaoSession getSession() \{

return mDaoSession;

public DaoSession getNewSession() \{

mDaoSession = mDaoMaster.newSession();

return mDaoSession;

/\*private static class AppOpenHelper extends DaoMaster.OpenHelper \{

public AppOpenHelper(Context context, String name) \{

super(context, name);

public AppOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) \{

super(context, name, factory);

@Override

public void onUpgrade(Database db, int oldVersion, int newVersion) \{

DaoSession daoSession = new DaoMaster(db).newSession();

// TODO: do something before recreate tables

DaoMaster.dropAllTables(db, true);

onCreate(db);

@Override

public void onCreate(Database db) \{

Log.i("greenDAO", "Creating tables for schema version " + DaoMaster.SCHEMA\_VERSION);

DaoMaster.createAllTables(db, true);

\}\*/

public class MySQLiteOpenHelper extends DaoMaster.OpenHelper \{

public MySQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) \{

super(context, name, factory);

@Override

public void onUpgrade(Database db, int oldVersion, int newVersion) \{

MigrationHelper.migrate(db, new MigrationHelper.ReCreateAllTableListener() \{

@Override

public void onCreateAllTables(Database db, boolean ifNotExists) \{

DaoMaster.createAllTables(db, ifNotExists);

@Override

public void onDropAllTables(Database db, boolean ifExists) \{

DaoMaster.dropAllTables(db, ifExists);

\},DBCurrentUserDao.class, DBCurrentUserSettingDao.class, DBTextChatMessageDao.class,RelationUserDao.class);

主要代码：

public class MySQLiteOpenHelper extends DaoMaster.OpenHelper {
        public MySQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
            super(context, name, factory);
        }
        @Override
        public void onUpgrade(Database db, int oldVersion, int newVersion) {
            MigrationHelper.migrate(db, new MigrationHelper.ReCreateAllTableListener() {
    
                @Override
                public void onCreateAllTables(Database db, boolean ifNotExists) {
                    DaoMaster.createAllTables(db, ifNotExists);
                }
    
                @Override
                public void onDropAllTables(Database db, boolean ifExists) {
                    DaoMaster.dropAllTables(db, ifExists);
                }
            },DBCurrentUserDao.class, DBCurrentUserSettingDao.class, DBTextChatMessageDao.class,RelationUserDao.class);
        }
    }