Panel类new一个对象

Question

public class CheckInPanel extends JPanel {……}  ……  在其他的类中CheckInPanel c=new CheckInPanel();为什么都会报错can't find symbol；symbol:constructor CheckInPanel(),location:class client.CheckInPanel at line 17如果想在其他类中调用CheckInPanel的对象应该怎么写代码

Answer 1

CheckInPanel 这个类定义的代码贴一下,是不是构造方法有问题.

Answer 2

package com.jbaptech.accp.netbar.client;import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.text.*;
import java.util.*;
import com.jbaptech.accp.netbar.server.entity.*;
import com.jbaptech.accp.netbar.server.dao.ComputerDAO;
import com.jbaptech.accp.netbar.server.action.BusinessAction;
public class CheckInPanel extends JPanel {
  JLabel computerIdDescLabel = new JLabel();
  JLabel cardIdDescLabel = new JLabel();
  JTextField cardIdTextField = new JTextField();
  JLabel pwdDescLabel = new JLabel();
  JLabel dispalyNowTimeDescLabel = new JLabel();
  JTextField dispalyNowTimeTextField = new JTextField();
  JButton confirmButton = new JButton();
  JButton resetButton = new JButton();
  JPasswordField passwordFiled = new JPasswordField();
  JComboBox computerIdCombox = new JComboBox();
  java.util.Date nowTime;
  public CheckInPanel(NetBarFeeMangementFrame mFrame) {
    try {
      mainFrame = mFrame;
      jbInit();
    }catch(Exception ex) {
      ex.printStackTrace();
    }
  }  void jbInit() throws Exception {
  this.setLayout(null);    computerIdDescLabel.setFont(new java.awt.Font("Serif", 0, 13));
    computerIdDescLabel.setHorizontalAlignment(SwingConstants.CENTER);
    computerIdDescLabel.setText("机器号码：");
    computerIdDescLabel.setBounds(new Rectangle(95, 30, 70, 25));    computerIdCombox.setBounds(new Rectangle(175, 30, 110, 25));    cardIdDescLabel.setFont(new java.awt.Font("Serif", 0, 13));
    cardIdDescLabel.setHorizontalAlignment(SwingConstants.CENTER);
    cardIdDescLabel.setText("卡        号：");
    cardIdDescLabel.setBounds(new Rectangle(95, 75, 70, 25));    cardIdTextField.setText("");
    cardIdTextField.setBounds(new Rectangle(175, 75, 110, 25));    pwdDescLabel.setFont(new java.awt.Font("Serif", 0, 13));
    pwdDescLabel.setHorizontalAlignment(SwingConstants.CENTER);
    pwdDescLabel.setText("密        码：");
    pwdDescLabel.setBounds(new Rectangle(95, 120, 70, 25));    passwordFiled.setText("");
    passwordFiled.setBounds(new Rectangle(175, 120, 110, 25));    dispalyNowTimeDescLabel.setFont(new java.awt.Font("Serif", 0, 13));
    dispalyNowTimeDescLabel.setHorizontalAlignment(SwingConstants.CENTER);
    dispalyNowTimeDescLabel.setText("开始时间：");
    dispalyNowTimeDescLabel.setBounds(new Rectangle(95, 165, 70, 25));    nowTime = new java.util.Date();//nowTime:Thu Jul 31 09:07:01 CST 2008
    SimpleDateFormat HMFromat = new SimpleDateFormat("yyyy-MM-dd HH:mm");
    String dispalyNowTime = HMFromat.format(nowTime);
  
    dispalyNowTimeTextField.setText(dispalyNowTime);
    dispalyNowTimeTextField.setBounds(new Rectangle(175, 165, 110, 25));
    dispalyNowTimeTextField.setEnabled(false);    confirmButton.setBounds(new Rectangle(115, 215, 65, 25));
    confirmButton.setText("确认");
    confirmButton.addActionListener(new UseInPanel_confirmButton_actionAdapter(this));    resetButton.setBounds(new Rectangle(200, 215, 65, 25));
    resetButton.setText("重置");
    resetButton.addActionListener(new UseInPanel_resetButton_actionAdapter(this));    this.add(cardIdTextField, null);
    this.add(cardIdDescLabel, null);
    this.add(pwdDescLabel, null);
    this.add(dispalyNowTimeDescLabel, null);
    this.add(dispalyNowTimeTextField, null);
    this.add(passwordFiled, null);
    this.add(computerIdDescLabel, null);
    this.add(confirmButton, null);
    this.add(resetButton, null);
    this.add(computerIdCombox, null);    computerIdCombox.addItem("");
    ComputerDAO computerDAO=new ComputerDAO();//把向BusinessAction查询改为直接向ComputerDAO查询
    ArrayList list =computerDAO.getNoUsedComputerList();
    for(int i=0;i<list.size();i++){
        Computer computer = (Computer) list.get(i);//****
        computerIdCombox.addItem(computer.getId());
    }
  }  void resetButton_actionPerformed(ActionEvent e) {
  computerIdCombox.setSelectedIndex(0);
    cardIdTextField.setText("");
    passwordFiled.setText("");
  }  void confirmButton_actionPerformed(ActionEvent e) {
  String passwordtemp = "";
  int Login=1;
   String cardId = cardIdTextField.getText().trim();
   passwordtemp=passwordFiled.getText().toString();
   String computerId = computerIdCombox.getSelectedItem().toString();
   
    if(computerId.trim().length()==0){
      JOptionPane.showMessageDialog(this,"请选择机器号!","警告", JOptionPane.WARNING_MESSAGE ,null );
    Login=0;}
   if(cardId.length()==0){
      JOptionPane.showMessageDialog(this,"请输入卡号!","警告", JOptionPane.WARNING_MESSAGE ,null );
    Login=0;}
   if(passwordtemp.length()==0){
     JOptionPane.showMessageDialog(this,"请输入密码!","警告", JOptionPane.WARNING_MESSAGE ,null );
     Login=0;}
  
    String dispalyNowTime = dispalyNowTimeTextField.getText();//不加+":00",系统自动加入
   
     if(Login==1)
    {
    Card card = new Card();
    card.setId(cardId);//cardId = cardIdTextField.getText().trim();
    card.setPassword(passwordtemp);    Record record = new Record();
    record.setCardId(cardId);
    record.setComputerId(computerId);
    record.setBeginTime(dispalyNowTime);    Computer computer = new Computer();
    computer.setId(computerId);    if(BusinessAction.cardIsValid(card)){
          if(BusinessAction.cardHaveBalance(card)){
            BusinessAction.doStartUseComputerBusiness(record,computer);
          }else{
            JOptionPane.showMessageDialog(this,"卡余额不足，请充值!","警告", JOptionPane.WARNING_MESSAGE ,null );
      }
    }else{
      JOptionPane.showMessageDialog(this,"卡号或者密码不对!","警告", JOptionPane.WARNING_MESSAGE ,null );
    }
    }
    WelcomePanel welcomePanel2 = new WelcomePanel();
    mainFrame.remove(mainFrame.getContentPane());
    mainFrame.getContentPane().add(welcomePanel2);
    mainFrame.setContentPane(welcomePanel2);
    mainFrame.show();  }
  private NetBarFeeMangementFrame mainFrame;
}class UseInPanel_resetButton_actionAdapter implements java.awt.event.ActionListener {
  CheckInPanel adaptee;  UseInPanel_resetButton_actionAdapter(CheckInPanel adaptee) {
    this.adaptee = adaptee;
  }
  public void actionPerformed(ActionEvent e) {
    adaptee.resetButton_actionPerformed(e);
  }
}class UseInPanel_confirmButton_actionAdapter implements java.awt.event.ActionListener {
  CheckInPanel adaptee;  UseInPanel_confirmButton_actionAdapter(CheckInPanel adaptee) {
    this.adaptee = adaptee;
  }
  public void actionPerformed(ActionEvent e) {
    adaptee.confirmButton_actionPerformed(e);
  }
}

Answer 3

第17行package com.jbaptech.accp.netbar.server.dao;import com.jbaptech.accp.netbar.server.entity.Card;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Connection;
import java.sql.SQLException;
import com.jbaptech.accp.netbar.client.CheckInPanel;
public class CardDAO {
  public CardDAO() {
  }
  public  boolean cardIsValid(Card card) {
    boolean cardIsValid = false;
    Connection dbConnection = null;
    PreparedStatement pStatement = null;
    ResultSet res = null;
    CheckInPanel c=new CheckInPanel();
  
    try {
      dbConnection = ConnectionManager.getConnction();
      // 查询数据SQL语句
      String strSql = "select * from card where id='" + card.getId()//cardId =CheckInPanel. cardIdTextField.getText().trim();
          + "' and password ='" + card.getPassword() + "'";
      if (dbConnection != null) {
        System.out.println(dbConnection != null);
      }      //查询操作
      pStatement = dbConnection.prepareStatement(strSql);
      res = pStatement.executeQuery();
      if (res.next()) {
        cardIsValid = true;
      }
    } catch (SQLException sqlE) {
      sqlE.printStackTrace();
    } finally {
      ConnectionManager.closeStatement(pStatement);
      ConnectionManager.closeConnection(dbConnection);
    }
    return cardIsValid;
  }  public  boolean cardIsHaveBalance( Card card) {
    boolean haveBalance = false;
    Connection dbConnection = null;
    PreparedStatement pStatement = null;
    ResultSet res = null;
    try {
      dbConnection = ConnectionManager.getConnction();
      // 查询数据SQL语句
      String strSql = "select * from card where id='" + card.getId()
          + "' and password ='" + card.getPassword() + "'";
      if (dbConnection != null) {
        System.out.println(dbConnection != null);
      }
      //查询操作
      pStatement = dbConnection.prepareStatement(strSql);
      res = pStatement.executeQuery();
      if (res.next()) {
        int balance = res.getInt("balance");
        if (balance >= 2) {
          haveBalance = true;
        }
      }
    } catch (SQLException sqlE) {
      sqlE.printStackTrace();
    } finally {
      ConnectionManager.closeStatement(pStatement);
      ConnectionManager.closeConnection(dbConnection);
    }
    return haveBalance;
  }}

Answer 4

CheckInPanel()这个构造方法没有定义.
只能调用这个带参数的
public CheckInPanel(NetBarFeeMangementFrame mFrame)

Answer 5

楼主由于在类CheckInPanel 中提供了一个带参数的构造函数：
public CheckInPanel(NetBarFeeMangementFrame mFrame) ，
因此编译器不再提供默认的不带参数的构造函数，因此在其他的类在写如下代码：
CheckInPanel c=new CheckInPanel(); 
当然出错。