java - 关于 BlueJ 中按钮的几个问题

Question

我的问题是，当我选择单选按钮时，它会在 java 终端中导致巨大的错误。它在开始按钮(按钮1到按钮4)中，按钮1启动加油站(这样你就可以选择你想要的汽油类型)，但它没有打开单选按钮可供选择，而是给了我一堆错误，涉及到

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String

单选按钮之前可以工作，但在我使用复选框方法后，它停止工作，但复选框选择有效(但是没有清除)。发现错误了，就属于这个

litres=Double.parseDouble(gasL.getText());

所以我暂时删除了该部分，但不确定如何让它工作，因为我试图从用户可以输入的文本框中获取升数。煤气吧仍然没有打开

清除适用于复选框，但我不确定单选按钮，这给了我错误

这是我的代码

    import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
/**
 * A GUI for a Gas Bar, which allows you to choose the gas type you want, and optional car checks for things like 
 * windshield and gas check. The price is outputted afterwards.
 * 
 * @author Kevin Hy 
 * @date   08/06/13
 */
public class New_Gas_Bar extends JFrame
{
    public JPanel panel1,panel2,panel3,panel4,panel5;
    public JLabel main1, main2, main3,main4,main5,main6;
    public JLabel gasBar,total;
    public JButton button1,button2,button3,button4,clearGas,clearCar;
    public JRadioButton bronzeG,silverG,goldG,selfS,fullS,fullService,selfService;
    public JCheckBox oilC,windWash,pressureClock;
    public JTextField gasL;
    static double fullCost,selfCost,discount,gasCost,litres,cleaningC;
    static boolean boughtGas=false;

    public New_Gas_Bar()
    {
        super ("      New Gas Bar");
        setSize(640,640);
        Container container = getContentPane();

        panel1=new JPanel();
        panel2=new JPanel();
        panel3=new JPanel();
        panel4=new JPanel();
        panel5=new JPanel();

        panel1.setBackground(new Color(107,202,226));
        panel1.setLayout(new GridLayout(6,1));

        main1 = new JLabel ("         Gas Bar Project ");
        main2 = new JLabel ("         ICS4U0 - September 2013");
        main3 = new JLabel ("     ");
        main4 = new JLabel ("Enter Litres of Gas");
        main5 = new JLabel ("Select Full or Self Serve");
        main6 = new JLabel ("Select Gas Quality");

        button1 = new JButton ("Gas Station");
        button2 = new JButton ("Car Wash");
        button3 = new JButton ("Total");
        button4 = new JButton ("Exit");
        clearCar = new JButton ("Clear");
        clearGas = new JButton ("Clear");

        panel2.setBackground(new Color(144,160,170));
        panel2.setLayout(new FlowLayout ());
        panel2.add (button1);
        panel2.add (button2);
        panel2.add (button3);
        panel2.add (button4);
        panel1.add (main1);
        panel1.add (main2);
        panel1.add (main3);

        //container.setLayout(new BorderLayout());
        container.add(panel1,BorderLayout.NORTH);
        container.add(panel2,BorderLayout.CENTER);
        container.add(panel3,BorderLayout.EAST);
        container.add(panel4,BorderLayout.EAST);
        panel3.setBackground(new Color(107,202,226));
        panel4.setBackground(new Color(107,202,226));

        ButtonHandler handler = new ButtonHandler ();
        button1.addActionListener (handler);
        button2.addActionListener (handler);
        button3.addActionListener (handler);
        button4.addActionListener (handler);
        clearCar.addActionListener (handler);
clearGas.addActionListener (handler);
        ButtonGroup serveStyle = new ButtonGroup();
        fullS = new JRadioButton ("Full Serve");
        selfS = new JRadioButton ("Self Serve");
        serveStyle.add (fullS);
        serveStyle.add (selfS);

        ButtonGroup serveGas = new ButtonGroup();
        bronzeG = new JRadioButton("Bronze Service");
        silverG = new JRadioButton("Silver Service");
        goldG = new JRadioButton("Gold Service");
        serveGas.add (bronzeG);
        serveGas.add (silverG);
        serveGas.add (goldG);

        gasL = new JTextField(5);
        oilC = new JCheckBox("Oil Change");
        windWash = new JCheckBox("Windshield Wash");
        pressureClock = new JCheckBox("Air Pressure Check");

        RadioButtonHandler radioHand = new RadioButtonHandler ();
        bronzeG.addItemListener (radioHand);
        silverG.addItemListener (radioHand);
        goldG.addItemListener (radioHand);
        fullS.addItemListener (radioHand);
        selfS.addItemListener (radioHand);
        CheckBoxHandler checkHand = new CheckBoxHandler();
        oilC.addItemListener (checkHand);
        windWash.addItemListener (checkHand);
        pressureClock.addItemListener (checkHand);
        setVisible(true);
    }

    public static void main (String [] args)
    {

        New_Gas_Bar application = new New_Gas_Bar();    
    }

    public class ButtonHandler implements ActionListener

    {
        public void actionPerformed (ActionEvent event)
        {
            if (event.getSource () == button1)
            {           
                panel1.setVisible(true);
                panel2.setVisible(true);
                panel3.setVisible(true);
                panel4.setVisible(false);
                panel3.setLayout(new GridLayout(10,1));
                panel3.add(clearGas);
                panel3.add(main5);
                panel3.add(fullS);
                panel3.add(selfS);
                panel3.add(main6);
                panel3.add(bronzeG);
                panel3.add(silverG);
                panel3.add(goldG);
                panel3.add(main4);
                panel3.add(gasL);

                litres=Double.parseDouble(gasL.getText());
                //JOptionPane.showMessageDialog (null, litres);
            }
            else if (event.getSource () == button2)
            {
                panel1.setVisible(true);
                panel2.setVisible(true);
                panel3.setVisible(false);
                panel4.setVisible(true);
                panel4.setLayout(new FlowLayout ());
                panel4.add(clearCar);
                panel4.add(oilC);
                panel4.add(windWash);
                panel4.add(pressureClock);
            }
            else if (event.getSource () == button3)
            {
                JOptionPane.showMessageDialog (null, "This is your total:");
                JOptionPane.showMessageDialog (null, litres);
            }
            else if (event.getSource () == button4)
            {
                System.exit(0);
            }
            if (event.getSource () == clearGas)
            {
                JOptionPane.showMessageDialog (null, "Clearing All Selected Options");
                bronzeG.setSelected(false);
                silverG.setSelected(false);
                goldG.setSelected(false);
                fullS.setSelected(false);
                selfS.setSelected(false);
                gasCost=0;
                boughtGas=false;
            }
            if (event.getSource () == clearCar)
            {
                JOptionPane.showMessageDialog (null, "Clearing All Selected Options");
                pressureClock.setSelected(false);
                windWash.setSelected(false);
                oilC.setSelected(false);
                cleaningC=0;
            }
        }
    }
    public class RadioButtonHandler implements ItemListener

    {
        public void itemStateChanged(ItemEvent event)
        {
            if (event.getSource () == fullS)
            {        
                JOptionPane.showMessageDialog (null, "Full Serve Selected");
                fullCost =1.25;
                boughtGas=true;
            }

            else if (event.getSource () == selfS)
            {
                JOptionPane.showMessageDialog (null, "Self Serve Selected");
                selfCost =0.60;
                boughtGas=true;
            }
            if (event.getSource () == bronzeG)
            {           
                JOptionPane.showMessageDialog (null, "Bronze Gas Option Selected");
                gasCost=0.50;
                boughtGas=true;
            }
            if (event.getSource () == silverG)
            {
                JOptionPane.showMessageDialog (null, "Silver Gas Option Selected");
                gasCost=0.75;
                boughtGas=true;
            }
            if (event.getSource () == goldG)
            {
                JOptionPane.showMessageDialog (null, "Gold Gas Option Selected");
                gasCost=0.95;
                boughtGas=true;
            }

        }
    }
    public class CheckBoxHandler implements ItemListener

    {
        public void itemStateChanged (ItemEvent event)
        {
            if (event.getSource () == oilC)
            {           
                JOptionPane.showMessageDialog (null, "Oil Cleaning Selected");
                if (boughtGas==true)
                {
                    cleaningC+=10.00;
                }
                else 
                {
                    cleaningC+=12.50;
                }
            }
            if (event.getSource () == windWash)
            {
                JOptionPane.showMessageDialog (null, "Windshield Washing Selected");
                if (boughtGas==true)
                {
                    cleaningC+=10.00;
                }
                else 
                {
                    cleaningC+=12.50;
                }
            }
            if (event.getSource () == pressureClock)
            {
                JOptionPane.showMessageDialog (null, "Air Pressure Check Selected");
                if (boughtGas==true)
                {
                    cleaningC+=10.00;
                }
                else 
                {
                    cleaningC+=12.50;
                }
            }

        }
    }
}

Answer 1

查看您收到的错误。它说 NumberFormatException。我相信问题出在你的 Double.parseDouble(gasL.getText()) 上。当gasL留空时会发生什么？程序如何将空字符串解析为 double 字符串？尝试将 GasL 的默认值设置为 0 或查看 try/catch 来处理异常。

gasL = new JTextField("0",5);

这会删除错误消息，但我无法弄清楚为什么您的加油站面板无法打开，对此表示抱歉。