public  class DBHelper extends SQLiteOpenHelper{ 
 
 	
	public final static String DATABASENAME ="diaryOpenHelper.db";
	public final static int DATABASEVERSION =1; 
 
 
	
	//创建数据库
	public 
DBHelper(Context 
context,Stringname,CursorFactory factory,int version){ 

		super(context, name, factory,version);
	} 
 
	
	//创建表等机构性文件 
 
	public void onCreate(SQLiteDatabase db){ 

		String sql ="create tablediary"+"("_id integer primary key autoincrement,"+"topic varchar(100),"+"content varchar(1000)"+")"; 
		db.execSQL(sql);
	} 

	
	//若数据库版本有更新，则调用此方法 
 
	public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){
		
String sql = "drop table ifexists diary"; 
		db.execSQL(sql); 
 		this.onCreate(db);

 	} 
    }