最近在做項目的時候，為了方便測試人員測試，在應用中加入正式庫和測試庫切換的功能。為了防止正式庫和測試庫切換帶來的數據沖突，切換的時候必須把當前的數據庫清空。代碼如下：

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){};
    }
 
    /**
     * 獲取單例引用
     *
     * @param context
     * @return
     */
    public static DBManager getInstance(Context context) {
        if (mInstance == null) {
            synchronized (DBManager.class) {
                if
 
 (mInstance == null) {
                    mInstance = new DBManager(context);
                }
            }
        }
        return mInstance;
    }
 
    /**
     * 獲取可讀數據庫
     */
    private SQLiteDatabase getReadableDatabase() {
        if (openHelper == null) {
            openHelper = new MySQLiteOpenHelper(context, dbName, null);
        }
        SQLiteDatabase db = openHelper.getReadableDatabase();
        return db;
    }
 
    /**
     * 獲取可寫數據庫
     */
    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);
        }
    }
 
}

必須要加上DaoMaster.createAllTables(daoMaster.getDatabase(),true),不然重新進行數據庫操作的時候（crud）會報找不到數據庫表的錯誤：Caused by: android.database.sqlite.SQLiteException: no such table: 表名 ，至於為什麽不會重新創建數據庫表，我也不知道為啥，在這上面也浪費了一些時間，所以寫下這篇博客。

Android GreenDao清空數據庫的方法