GreenDao清空数据库的方法

来源：互联网发布：软件系统可靠性设计编辑：程序博客网时间：2024/05/18 03:36

最近在做项目的时候，为了方便测试人员测试，在应用中加入正式库和测试库切换的功能。为了防止正式库和测试库切换带来的数据冲突，切换的时候必须把当前的数据库清空。代码如下：

package com.example.admin.greendaotest;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import com.greendao.gen.DaoMaster;import org.greenrobot.greendao.database.Database;/** * Created by admin on 2017/9/19. */public class DBManager {    private final static String dbName = "student_db";    private static DBManager mInstance;    private DaoMaster.OpenHelper openHelper;    private Context context;    public DBManager(Context context) {        this.context = context;        openHelper = new DaoMaster.OpenHelper(context, dbName, null){};    }    /**     * 获取单例引用     *     * @param context     * @return     */    public static DBManager getInstance(Context context) {        if (mInstance == null) {            synchronized (DBManager.class) {                if (mInstance == null) {                    mInstance = new DBManager(context);                }            }        }        return mInstance;    }    /**     * 获取可读数据库     */    private SQLiteDatabase getReadableDatabase() {        if (openHelper == null) {            openHelper = new MySQLiteOpenHelper(context, dbName, null);        }        SQLiteDatabase db = openHelper.getReadableDatabase();        return db;    }    /**     * 获取可写数据库     */    private SQLiteDatabase getWritableDatabase() {        if (openHelper == null) {            openHelper = new MySQLiteOpenHelper(context, dbName, null);        }        SQLiteDatabase db = openHelper.getWritableDatabase();        return db;    }    public void deleSQL(){        SQLiteDatabase db=getWritableDatabase();        DaoMaster daoMaster = new DaoMaster(db);        DaoMaster.dropAllTables(daoMaster.getDatabase(),true);        DaoMaster.createAllTables(daoMaster.getDatabase(),true);    }    class MySQLiteOpenHelper extends DaoMaster.OpenHelper{        @Override        public void onCreate(Database db) {            super.onCreate(db);        }        public MySQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {            super(context, name, factory);        }    }}

必须要加上DaoMaster.createAllTables(daoMaster.getDatabase(),true),不然重新进行数据库操作的时候（crud）会报找不到数据库表的错误：Caused by: android.database.sqlite.SQLiteException: no such table: 表名，至于为什么不会重新创建数据库表，我也不知道为啥，在这上面也浪费了一些时间，所以写下这篇博客。

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