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Sqlite 发布时间：2022-05-22 发布网站：大佬教程 code.js-code.com

大佬教程收集整理的这篇文章主要介绍了SQLite Database判断是否存在、新建、删除.....，大佬教程大佬觉得挺不错的，现在分享给大家，也给大家做个参考。

　AndroID sqlite Database本打算封装sqlite的，但是，发现实际上AndroID已经封装了一层，尤其是数据的增、删、查、改上，更是如此，所以，我后来只封装了一个连接层，负责打开、建立数据库，并返回一个sqlite的实例用来完成增、删、插、改等操作。

//----------- DBHelper -------------

package utility.db;

import java.io.fileNotFoundException;

import androID.content.Context;
import androID.database.sqlite.sqliteDatabase;
import androID.database.sqlite.sqliteDatabase.cursorFactory;

public class DBHelper
{
private sqliteDatabase db = null;

private Context ctx = null;

public DBHelper( Context ctx )
{
this.ctx = ctx;
}

/**
* 判断数据库是否存在
*
* @param dbname
* 数据库名称
* @return true存在 false不存在
*/
public Boolean exist( String dbname )
{
Log.log("called fun : exist()");
Boolean flag = false;
try
{
db = ctx.openDatabase(dbname,null);
Log.log("database/"+dbname+" exist");
flag = true;
}
catch (fileNotFoundException E)
{
flag = false;
Log.log("database/"+dbname+" not exist");
}
finally
{
if (db != null)
db.close();
db = null;
}
return flag;
}

/**
* 打开数据库
*
* @param dbname
* 数据库名称
* @return true 打开成功 false打开失败
*/
public Boolean openDatabase( String dbname,Boolean created )
{
return openDatabase(dbname,null,created);
}

/**
* 打开数据库
*
* @param dbname
* 数据库名称
* @param factory
* @return true 打开成功 false打开失败
*/
public Boolean openDatabase( String dbname,cursorFactory factory,
Boolean created )
{
Log.log("called fun : openDatabase()");
Log.log("called fun : if not exist then created "+dbname+" ? : "+created);
Boolean flag = false;
if(exist(dbName))
{
try
{
db = ctx.openDatabase(dbname,factory);
Log.log("database/"+dbname+" is opened");
flag = true;
}
catch (fileNotFoundException E)
{
Log.log("database/"+dbname+" is not opened");
flag = false;
}
}
else
{
if(created)
{
flag = createDatabase(dbname,1,factory);
}
else
{
flag = false;
}
}
return flag;

}

/**
* 创建数据库
*
* @param dbname
* 数据库名称
* @param version
* 数据库版本
* @param mode
* 模式
* @param factory
* @return true 建立成功 false 建立失败
*/
public Boolean createDatabase( String dbname,int version,int mode,
cursorFactory factory )
{
Log.log("called fun : createDatabase()");
Boolean flag = false;
try
{
db = ctx.createDatabase(dbname,version,mode,factory);
Log.log("database/"+dbname+" is created successfully!");
flag = true;
}
catch (fileNotFoundException E)
{
Log.log("database/"+dbname+" can't be created");
flag = true;
}
return flag;
}

/**
* 建立数据库
*
* @param dbname
* 数据库名称
* @return true 打开成功 false 打开失败
*/
public Boolean createDatabase( String dbname )
{
return createDatabase(dbName);
}

/**
* 关闭数据库
*
*/
public voID closeDatabase()
{
Log.log("close database");
if (db != null)
db.close();
db = null;
ctx = null;
}
/**
* 删除表
* @param tablename 表名
* @return 成功则返回表名失败则返回null
*/
public String droptable( String tablename )
{
Log.log("called fun droptable()");
if (tablename == null)
{
Log.log("table name is error! "+tablename+" is null !");
return null;
}
String DROP_table = "drop table IF EXISTS " + tablename;
db.execsql(DROP_tablE);
Log.log("table/"+tablename+" is dropped successfully");
return tablename;
}
/**
* 取得数据库实例
* @return 返回数据库实例
*/
public sqliteDatabase getDBInstance()
{
return db;
}
public Boolean execsql(String sql)
{
Boolean flag = false;
Log.log("called fun execsql()");
Log.log("sql:"+sql);
try
{
db.execsql(sql);
Log.log("sql exec successfully!");
flag = true;
}
catch(Exception E)
{
Log.log("sql exec not successfully!");
flag = false;
}
return flag;
}