网上搜索很多都是3.0以下的版本数据迁移配置，在此记录自己3.2.2版本的数据迁移的配置
1.修改之前的数据迁移类
public class MigrationHelper {
private static MigrationHelper instance;
public static MigrationHelper getInstance() {
if(instance == null) {
instance = new MigrationHelper();
}
return instance;
}
public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
generateTempTables(db, daoClasses);
DaoMaster.dropAllTables(db, true);
DaoMaster.createAllTables(db, false);
restoreData(db, 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) {
Log.e(TAG,exception.toString());
}
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()));
Log.e(TAG,exception.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;
}
}
2.创建一个类继承 DaoMaster.OpenHelper
public class UpdateOpenHelper extends DaoMaster.OpenHelper {
public UpdateOpenHelper(Context context, String name) {
super(context, name);
}
public UpdateOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
super(context, name, factory);
}
//此方法用于3.0版本之前的升级方案 须将MigrationHelper中的DB 类型更改为SQLiteDatabase
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
super.onUpgrade(db, oldVersion, newVersion);
if (oldVersion < newVersion) {
Log.i("version", oldVersion + "---先前和更新之后的版本---" + newVersion);
// MigrationHelper.getInstance().migrate(db, UserDao.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);
}
}
@Override
public void onUpgrade(Database db, int oldVersion, int newVersion) {
super.onUpgrade(db, oldVersion, newVersion);
Log.i("version", oldVersion + "---先前和更新之后的版本---" + newVersion);
if (oldVersion < newVersion) {
MigrationHelper.getInstance().migrate(db, UserDao.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);
}
}
}
3.修改GreenDao的初始化
修改前的初始化
mHelper = new DaoMaster.DevOpenHelper(this, "test-db.db", null);
db = mHelper.getWritableDatabase();
// 注意：该数据库连接属于 DaoMaster，所以多个 Session 指的是相同的数据库连接。
mDaoMaster = new DaoMaster(db);
mDaoSession = mDaoMaster.newSession();
//获取对应的数据库表对象
userDao = mDaoSession.getUserDao();
修改后
mHelper = new UpdateOpenHelper(this, "test-db.db", null);
db = mHelper.getWritableDatabase();
// 注意：该数据库连接属于 DaoMaster，所以多个 Session 指的是相同的数据库连接。
mDaoMaster = new DaoMaster(db);
mDaoSession = mDaoMaster.newSession();
//获取对应的数据库表对象
userDao = mDaoSession.getUserDao();
我的DB管理类
public class DBManager {
// 是否加密
public static final boolean ENCRYPTED = true;
private static final String DB_NAME = "test-db.db";
private static DbManager mDbManager;
private static DaoMaster.DevOpenHelper mDevOpenHelper;
private static DaoMaster mDaoMaster;
private static DaoSession mDaoSession;
private Context mContext;
private DBManager(Context context) {
this.mContext = context;
// 初始化数据库信息
mDevOpenHelper = new DaoMaster.DevOpenHelper(context, DB_NAME);
getDaoMaster(context);
getDaoSession(context);
}
public static DBManager getInstance(Context context) {
if (null == mDBManager) {
synchronized (DBManager.class) {
if (null == mDBManager) {
mDBManager = new DBManager(context);
}
}
}
return mDBManager;
}
/**
* 获取可读数据库
*
* @param context
* @return
*/
public static SQLiteDatabase getReadableDatabase(Context context) {
if (null == mDevOpenHelper) {
getInstance(context);
}
return mDevOpenHelper.getReadableDatabase();
}
/**
* 获取可写数据库
*
* @param context
* @return
*/
public static SQLiteDatabase getWritableDatabase(Context context) {
if (null == mDevOpenHelper) {
getInstance(context);
}
return mDevOpenHelper.getWritableDatabase();
}
/**
* 获取DaoMaster
*
* 判断是否存在数据库，如果没有则创建数据库
* @param context
* @return
*/
public static DaoMaster getDaoMaster(Context context) {
if (null == mDaoMaster) {
synchronized (DbManager.class) {
if (null == mDaoMaster) {
UpdateOpenHelper helper = new UpdateOpenHelper(context,DB_NAME,null);
mDaoMaster = new DaoMaster(helper.getWritableDatabase());
}
}
}
return mDaoMaster;
}
/**
* 未添加版本更新前的获取方法
* 获取DaoMaster
*
* @param context
* @return
*/
// public static DaoMaster getDaoMaster(Context context) {
// if (null == mDaoMaster) {
// synchronized (DbManager.class) {
// if (null == mDaoMaster) {
//
// mDaoMaster = new DaoMaster(getWritableDatabase(context));
// }
// }
// }
// return mDaoMaster;
// }
/**
* 获取DaoSession
*
* @param context
* @return
*/
public static DaoSession getDaoSession(Context context) {
if (null == mDaoSession) {
synchronized (DbManager.class) {
mDaoSession = getDaoMaster(context).newSession();
}
}
return mDaoSession;
}
}
4.注意事项
实体类中新增字段，必须为Long,Double,Integer,Float,String类型，否则在数据迁移时会出现空指针异常
你可以查看对应的Dao类中createTable（）方法 double等类型会在字段后出现REAL NOT NULL
/** Creates the underlying database table. */
public static void createTable(Database db, boolean ifNotExists) {
String constraint = ifNotExists? "IF NOT EXISTS ": "";
db.execSQL("CREATE TABLE " + constraint + "\"USER\" (" + //
"\"_id\" INTEGER PRIMARY KEY AUTOINCREMENT ," + // 0: id
"\"NAME\" TEXT," + // 1: name
"\"PASSWORD\" TEXT," + // 2: password
"\"AGE\" TEXT," + // 3: age
"\"A\" REAL NOT NULL );"); // 4: a 为double类型
}
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