在android中升级sqlite表

我有一个名为3列的人.他们是ID,NAME和PASSWORD.我需要添加一个名为AGE的新专栏.我试试这种方式但它对我不起作用请帮助我克服这个问题

public class Userdb {
    public static final String KEY_ROWID = "Id";
    public static final String KEY_NAME = "Person_name";
    public static final String KEY_PASSWORD = "Person_password";
    public static final String KEY_AGE = "Person_age";

    private static final String DATABASE_NAME = "People_db_1";
    private static final String DATABASE_TABLE = "people_table";
    private static final int DATABASE_VERSION = 1;


    private static class Dbhelper extends SQLiteOpenHelper {

        public Dbhelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            // TODO Auto-generated constructor stub
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            // TODO Auto-generated method stub

            db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + KEY_ROWID
                    + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_NAME
                    + " TEXT NOT NULL, " + KEY_PASSWORD + " TEXT NOT NULL); ");

        }


        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            // TODO Auto-generated method stub

            db.execSQL("DROP TABLE IF EXISTS" + DATABASE_TABLE);
            db.execSQL("ALTER TABLE " + DATABASE_TABLE +" ADD COLUMN "+ KEY_AGE +" TEXT NOT NULL ; ");
            onCreate(db);

        }

    }

数据库升级

SQLiteOpenHelper实现的构造函数应该调用超级构造函数,传递数据库名称和版本.仅当版本整数大于模拟器中运行的当前版本时,才会调用onUpgrade()方法.如果要调用onUpgrade()方法,则需要在代码中增加版本号.

关于onCreate()和onUpgrade()的See More