package cn.learn.db.util; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.database.sqlite.SQLiteDatabase.CursorFactory; public class DBHelper extends SQLiteOpenHelper {  private final static String DB_NAME ="test.db";//数据库名  private final static int VERSION = 1;//版本号  //自带的构造方法  public DBHelper(Context context, String name, CursorFactory factory,    int version) {   super(context, name, factory, version);  }  //为了每次构造时不用传入dbName和版本号，自己得新定义一个构造方法  public DBHelper(Context cxt){   this(cxt, DB_NAME, null, VERSION);//调用上面的构造方法  }  //版本变更时  public DBHelper(Context cxt,int version) {   this(cxt,DB_NAME,null,version);  }  //当数据库创建的时候调用  public void onCreate(SQLiteDatabase db) {   String sql = "create table student(" +       "id integer primary key autoincrement," +       "name varchar(20)," +       "age int)";   db.execSQL(sql);  }  //版本更新时调用  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {   String sql  = "update student ....";//自己的Update操作   db.execSQL(sql);  } }

package cn.learn.db.dao; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import cn.learn.db.dao.domain.Student; import cn.learn.db.util.DBHelper; public class StudentDao {  DBHelper helper = null;  public StudentDao(Context cxt) {   helper = new DBHelper(cxt);  }  /**   * 当Activity中调用此构造方法，传入一个版本号时，系统会在下一次调用数据库时调用Helper中的onUpgrade()方法进行更新   * @param cxt   * @param version   */  public StudentDao(Context cxt, int version) {   helper = new DBHelper(cxt, version);  }  // 插入操作  public void insertData(Student stu) {   String sql = "insert into student (name,age)values(?,?)";   SQLiteDatabase db = helper.getWritableDatabase();   db.execSQL(sql, new Object[] { stu.name, stu.age });  }  // 其它操作 }