Java选项卡式窗格未显示程序

Question

I'm fairly inexperienced with Java and have searched around quite a bit to resolve this issue. I believe I have the code correct but my tabs are not showing anything. I came across something about changing the layout to BorderLayout but it didn't work for me. When I run the program I can see a very quick glimpse of my first tab program then it's blank. I posted just the TabbedPrograms class because I believe the problem lies in here but I can post the rest if needed. Thank you in advance for any help.

import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JTabbedPane;


public class TabbedPrograms extends JFrame
{
public TabbedPrograms()
{
    setTitle("Week Four Lab Assignment");
    setLayout(new BorderLayout()); //this is what I added to change from the default layout
    JTabbedPane jtp = new JTabbedPane();
    getContentPane().add(jtp);

    jtp.addTab("Day GUI", new DayGUI());
    jtp.addTab("Office Area Calculator", new OfficeAreaCalculator());

    getContentPane().add(jtp);
    setSize(310, 210);
    setVisible(true);
}

public static void main(String[] args) 
{
    TabbedPrograms test = new TabbedPrograms();
    test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}

import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class DayGUI extends JPanel 
{
private JFrame mainFrame;
private JButton cmdGood;
private JButton cmdBad;

public DayGUI()
{
    mainFrame = new JFrame("Messages");

    cmdGood = new JButton("Good");
    cmdBad = new JButton("Bad");

    Container c = mainFrame.getContentPane();
    c.setLayout(new FlowLayout());
    c.setBackground(Color.orange);

    c.add(cmdGood);
    c.add(cmdBad);

    cmdGood.setMnemonic('G');
    cmdBad.setMnemonic('B');

    mainFrame.setSize(300, 100);

    mainFrame.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }

});

    ButtonsHandler bhandler = new ButtonsHandler();
    cmdGood.addActionListener(bhandler);
    cmdBad.addActionListener(bhandler);

    mainFrame.setVisible(true);
}

class ButtonsHandler implements ActionListener
{
    public void actionPerformed(ActionEvent e) {

        if(e.getSource() == cmdGood)
            JOptionPane.showMessageDialog(null, "Today is a good day!",
                    "Event Handler Message",
                    JOptionPane.INFORMATION_MESSAGE);

        if(e.getSource() == cmdBad)
            JOptionPane.showMessageDialog(null, "Today is a bad day!",
                    "Event Handler Message",
                    JOptionPane.INFORMATION_MESSAGE);
    }
}

public static void main(String[] args) 
{
    DayGUI app;
    app = new DayGUI();

}

}


import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.text.DecimalFormat;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class OfficeAreaCalculator extends JPanel
{
private JFrame mainFrame;
private JButton calculateButton;
private JButton exitButton;
private JTextField lengthField;
private JTextField widthField;
private JTextField areaField;
private JLabel lengthLabel;
private JLabel widthLabel;
private JLabel areaLabel;

public OfficeAreaCalculator()
{
    mainFrame = new JFrame("Office Area Calculator");

    exitButton = new JButton("Exit");
    lengthLabel = new JLabel("Enter the length of the office:");
    widthLabel = new JLabel("Enter the width of the office:");
    areaLabel = new JLabel("Office area:");
    lengthField = new JTextField(5);
    widthField = new JTextField(5);
    areaField = new JTextField(5);
    areaField.setEditable(false);
    calculateButton = new JButton("Calculate");

    Container c = mainFrame.getContentPane();

    c.setLayout(new FlowLayout());

    c.add(lengthLabel);
    c.add(lengthField);
    c.add(widthLabel);
    c.add(widthField);
    c.add(areaLabel);
    c.add(areaField);
    c.add(calculateButton);
    c.add(exitButton);

    calculateButton.setMnemonic('C');
    exitButton.setMnemonic('X');

    mainFrame.setSize(260, 150);

    mainFrame.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    });


    CalculateButtonHandler chandler = new CalculateButtonHandler();
    calculateButton.addActionListener(chandler);

    ExitButtonHandler ehandler = new ExitButtonHandler();
    exitButton.addActionListener(ehandler);

    FocusHandler fhandler = new FocusHandler();
    lengthField.addFocusListener(fhandler);
    widthField.addFocusListener(fhandler);
    areaField.addFocusListener(fhandler);

    mainFrame.setVisible(true);
        }

class CalculateButtonHandler implements ActionListener
{
    public void actionPerformed(ActionEvent e)
    {
        DecimalFormat num = new DecimalFormat(", ###.##");
        double width, length, area;
        String instring;

        instring = lengthField.getText();
        if(instring.equals(""))
        {
            instring = ("0");
            lengthField.setText("0");
        }
        length = Double.parseDouble(instring);

        instring = widthField.getText();
        if(instring.equals(""))
        {
            instring = "0";
            widthField.setText("0");
        }
        width = Double.parseDouble(instring);

        area = length * width;
        areaField.setText(num.format(area));

    }
}

class ExitButtonHandler implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        System.exit(0);
    }
}

class FocusHandler implements FocusListener
{
    public void focusGained(FocusEvent e)
    {
        if(e.getSource() == lengthField || e.getSource() == widthField)
        {
            areaField.setText("");
        }
        else if (e.getSource() == areaField)
        {
            calculateButton.requestFocus();
        }
    }

    public void focusLost(FocusEvent e)
    {
        if(e.getSource() == widthField)
        {
            calculateButton.requestFocus();
        }
    }
}

}

Answer 1

The problem is that both DayGUI and OfficeAreaCalculator both add components to to their own individual JFrame windows rather than to TabbedPrograms . Those frames appear simultaneously then the main application frame is displayed.

In both those containers add the components directly onto the JPanel so that the components appear on the JTabbedPane

For example

//c.add(lengthLabel);
add(lengthLabel);

Answer 2

Something is wrong with your code logic, you wish to add a Day() and Calc() objects to your JTabbedPane, both of which extend JPanel, which you should use and add elements to when you add them to your tabbed pane. Instead in your Day() and Calc() objects you instantiate new JFrame() objects which I don't seem to see (getters) inside your main function.