GreenDao数据库升级

在将apk发包出去后需要改动Entity的元素，就需要升级数据库。
这时看具体需求，一是不需要原有数据，清除数据库；二是需要保留原有数据。
greendao默认使用的是第一种：
Daomaster:

   public static class DevOpenHelper extends OpenHelper {
        public DevOpenHelper(Context context, String name) {
            super(context, name);
        }

        public DevOpenHelper(Context context, String name, CursorFactory factory) {
            super(context, name, factory);
        }

        @Override
        public void onUpgrade(Database db, int oldVersion, int newVersion) {
            Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables");
            dropAllTables(db, true);
            onCreate(db);
        }
    }

这里只说第二种情况。
那么需要升级需要如下操作：

• 自定义 Daomaster ,在 Application中申明
• 更改数据库版本号
• 添加需要增加的字段

在 CameraTime 中增加 test属性

@Entity
public class CameraTime {
    @Id
    private Long id;
    private String time;
    private String standUuid;

    public String test;
}

• MyDaoMaster：

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

import org.greenrobot.greendao.AbstractDaoMaster;
import org.greenrobot.greendao.AbstractDaoSession;
import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.database.DatabaseOpenHelper;
import org.greenrobot.greendao.identityscope.IdentityScopeType;

/**
 * Created by zhangli
 *
 * @time 2018/1/5
 */

public class MyDaoMaster  extends AbstractDaoMaster {
    public static final int SCHEMA_VERSION = 2;

    public MyDaoMaster(Database db, int schemaVersion) {
        super(db, schemaVersion);
    }

    @Override
    public AbstractDaoSession newSession() {
        return null;
    }

    @Override
    public AbstractDaoSession newSession(IdentityScopeType type) {
        return null;
    }

    public static void createAllTables(Database db, boolean ifNotExists) {
        CameraEntityDao.createTable(db, ifNotExists);
        CameraTimeDao.createTable(db, ifNotExists);
        FaroEntityDao.createTable(db, ifNotExists);
        FaroFileDao.createTable(db, ifNotExists);
        FloorPlanPictureDao.createTable(db, ifNotExists);
        PictureMatrixDao.createTable(db, ifNotExists);
        ProjectDao.createTable(db, ifNotExists);
        StandingEntityDao.createTable(db, ifNotExists);
        UpDataIdDao.createTable(db, ifNotExists);
        UserDao.createTable(db, ifNotExists);
        ImageRowDao.createTable(db, ifNotExists);
    }

    /** Drops underlying database table using DAOs. */
    public static void dropAllTables(Database db, boolean ifExists) {
        CameraEntityDao.dropTable(db, ifExists);
        CameraTimeDao.dropTable(db, ifExists);
        FaroEntityDao.dropTable(db, ifExists);
        FaroFileDao.dropTable(db, ifExists);
        FloorPlanPictureDao.dropTable(db, ifExists);
        PictureMatrixDao.dropTable(db, ifExists);
        ProjectDao.dropTable(db, ifExists);
        StandingEntityDao.dropTable(db, ifExists);
        UpDataIdDao.dropTable(db, ifExists);
        UserDao.dropTable(db, ifExists);
        ImageRowDao.dropTable(db, ifExists);
    }

    public static abstract class OpenHelper extends DatabaseOpenHelper {
        public OpenHelper(Context context, String name) {
            super(context, name, SCHEMA_VERSION);
        }

        public OpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
            super(context, name, factory, SCHEMA_VERSION);
        }

        @Override
        public void onCreate(Database db) {
            Log.i("greenDAO", "Creating tables for schema version " + SCHEMA_VERSION);
            createAllTables(db, false);
        }
    }

    /** WARNING: Drops all table on Upgrade! Use only during development. */
    public static class DevOpenHelper extends OpenHelper {
        public DevOpenHelper(Context context, String name) {
            super(context, name);
        }

        public DevOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
            super(context, name, factory);
        }

        @Override
        public void onUpgrade(Database db, int oldVersion, int newVersion) {
            Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables");
            switch (oldVersion) {
                case 1:
                    CameraTimeDao.createTable(db, true);
                    db.execSQL("ALTER TABLE 'CAMERA_TIME' ADD 'TEST' TEXT;");
                    break;
            }
        }
    }
}

在 onUpgrade 方法中，当旧版本号为1时，增加一个 test 的字段在 CameraTime 表中。
不知道数据库表的命名规则的话，可以将数据库导出本地打开看即可。

在 MyDaoMashter 和 build.gradle 中改变版本号

greendao {
    schemaVersion 2
    daoPackage 'com.build.scan.greendao.gen'
    targetGenDir 'src/main/java'
}

apk安装在版本号为1的的时候即可生效。