限制SQLite數據庫條目

Question

我開發了一個Android應用程序，這是一個試用版...其中用戶只有有限的設施..所以我想限制用戶輸入1 ...就像只有一個用戶名應該能夠註冊..和結果顯示有限制到4我有什麼該做的..我給右下面的代碼...

package com.example.loginpage; 

import android.content.Context; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteDatabase.CursorFactory; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.util.Log; 

public class DataBaseHelper extends SQLiteOpenHelper 

{ 

     public DataBaseHelper(Context context, String name,CursorFactory factory, int version) 
     { 
        super(context, name, factory, version); 


     } 


     // Called when no database exists in disk and the helper class needs 
     // to create a new one. 


     @Override 
     public void onCreate(SQLiteDatabase _db) 
     { 
       _db.execSQL(LoginDataBaseAdapter.DATABASE_CREATE); 

     } 



     // Called when there is a database version mismatch meaning that the version 
     // of the database on disk needs to be upgraded to the current version. 



     @Override 
     public void onUpgrade(SQLiteDatabase _db, int _oldVersion, int _newVersion) 
     { 



       // Log the version upgrade. 


       Log.w("TaskDBAdapter", "Upgrading from version " +_oldVersion + " to " +_newVersion + ", which will destroy all old data"); 

       // Upgrade the existing database to conform to the new version. Multiple 
       // previous versions can be handled by comparing _oldVersion and _newVersion 
       // values. 
       // The simplest case is to drop the old table and create a new one. 


       _db.execSQL("DROP TABLE IF EXISTS " + "TEMPLATE"); 


       // Create a new one. 


       onCreate(_db); 
     } 





} 

Answer 1

得到表計數採用Select Count(column Name) from tbalename和看跌期權的條件代碼if(count>=1){ //Message to user}