java - 未返回聚合查询结果内容

Question

我是一个初学者，我想根据我的项目的需求只允许一个用户注册。SIGNUP.java 是为了使用 DbHelper.java 来完成它，但对于 c.getCount() 来说一切正常，但对于 Integer.parseInt(c.getString(0)) 却不行

SIGNUP.java 内容如下：

package com.bishal.android.taskmanager;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class SIGNUP extends Activity {
    Button register;
    private EditText etName;
    private EditText etEmail;
    //private EditText etUsername;
    private EditText etPassword;
    private DbHelper dbhelper;

     AlertDialogManager alert = new AlertDialogManager();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.signup);
        dbhelper=new DbHelper(this);
        etName=(EditText)findViewById(R.id.edit_name);
        etEmail=(EditText)findViewById(R.id.edit_email);
        etPassword=(EditText)findViewById(R.id.edit_signup_password);
        register=(Button)findViewById(R.id.signup);
        final boolean bregister=(dbhelper.NoOfUser()==0)?true:false;
        register.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                // TODO Auto-generated method stub

                //String UserNameValue=etUsername.getText().toString();
                String NameValue=etName.getText().toString();
                String EmailValue=etEmail.getText().toString();
                String PasswordValue=etPassword.getText().toString();

                //Toast.makeText(SIGNUP.this,dbhelper.ThereIsUser(), Toast.LENGTH_LONG).show();
                if (bregister){
                ACCOUNT_INFO account=new ACCOUNT_INFO(NameValue,EmailValue,PasswordValue);
                if(NameValue.trim().length()>0 && EmailValue.trim().length() > 0 &&  PasswordValue.trim().length() >0){ 
                if(dbhelper.eMailValidation(EmailValue)){
                    if(dbhelper.validateregister(EmailValue)){
                    dbhelper.addAccount(account);
                    Toast.makeText(SIGNUP.this, "Your account has been sucessfully created.", Toast.LENGTH_LONG).show();
                    }
                else{
                    alert.showAlertDialog(SIGNUP.this, "Signup failed..", "Username/Email already exists.", false);
                }
            }
                else{
                    alert.showAlertDialog(SIGNUP.this,"Signup failed..", "Email address is not in such form.", false);
                }
        }
            else{
                alert.showAlertDialog(SIGNUP.this, "Signup failed..", "Please enter empty fields.", false);
            }
        }
    }
});

}

}

DbHelper.java 读取（为什么 'count' 不作为表中的行数返回？）：

    package com.bishal.android.taskmanager;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
//import android.widget.Toast;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class DbHelper extends SQLiteOpenHelper{

    private static final String TAG=DbHelper.class.getSimpleName();
    public static final String DB_NAME="Store Account.db";
    public static final int DB_VERSION=1;
    public static final String TABLE="Account_Info";
    public static final String COL_ID="Id";   //special for ID
    public static final String COL_NAME="Name";
    public static final String COL_EMAIL="Email";
    //public static final String COL_UNAME="Username";
    public static final String COL_PASSWORD="Password";

    public DbHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);

    }

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

                String CREATE_ACCOUNT_INFORMATION = "CREATE TABLE " + TABLE + "("
                + COL_ID + " INTEGER PRIMARY KEY," + COL_NAME + " String,"
                 + COL_EMAIL + " String," + COL_PASSWORD + " String" + ")";

        Log.d(TAG, "onCreate sql: "+CREATE_ACCOUNT_INFORMATION);
        db.execSQL(CREATE_ACCOUNT_INFORMATION);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
        db.execSQL("Drop Table If Exists " + TABLE);
        Log.d(TAG,"onUpdate dropped table "+ TABLE);
        onCreate(db);
    }


    void addAccount(ACCOUNT_INFO account){
        SQLiteDatabase db=this.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put(COL_NAME,account.getNAME());
        values.put(COL_EMAIL,account.getEMAIL());
        //values.put(COL_UNAME, account.getUSERNAME());
        values.put(COL_PASSWORD, account.getPASSWORD());
        db.insert(TABLE, null, values);
        db.close();
    }



    public boolean validateuser(String email,String password){
        Cursor c=getReadableDatabase().rawQuery("SELECT * FROM " + TABLE + " WHERE "
                + COL_EMAIL + "='" + email +"'AND "+COL_PASSWORD+"='" + password+"'" ,  null);
        if(c.getCount()>0)
            return true;
        else
            return false;
    }

    public boolean validateregister(String email){
        Cursor c=getReadableDatabase().rawQuery("SELECT * FROM " + TABLE + " WHERE "
                + COL_EMAIL + "='" + email+"'" ,  null);
        if(c.getCount()>0)
            return false;
        else
            return true;
    }

    public boolean eMailValidation(String emailValue) {
        final String EMAIL_PATTERN = 
                "^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@"
                + "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";
        Pattern pattern=Pattern.compile(EMAIL_PATTERN);;
        Matcher matcher;
        matcher = pattern.matcher(emailValue);
        return matcher.matches();
    }

    public int NoOfUser() {
        Cursor c=getReadableDatabase().rawQuery("SELECT count(*) FROM " + TABLE, null);
        int count=Integer.parseInt(c.getString(0));
        return count;
    }
}