Android GreenDao清空数据库的方法

Posted 2020-12-04 星辰

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。