创建JTable以显示数据的麻烦

Question

我正在为学校做这个薪资项目。 这个想法是让用户从ComboBox输入员工的姓名，工作时间，小时费率和选择部门。 将显示3个按钮，＆＃34;添加更多＆＃34;，＆＃34;显示结果＆＃34;和＆＃34;退出＆＃34;。 ＆＃34;添加更多＆＃34;按钮将输入存储到几个arryalist并将文本字段设置为空白以允许更多输入。 ＆＃34;显示结果＆＃34;将在底部JPanel生成一个JTable，以显示员工的姓名，部门和周薪。

我遇到的问题是在点击＆＃34;显示结果＆＃34;按钮。也许我误解了按钮事件的目的，但我现在真的很困惑。请帮忙！

这是UI的photobucket directURL PrtSc，希望它有所帮助。

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;

public class PayrollFrame extends JFrame
{
    private JLabel nameMessageLabel, hourMessageLabel, rateMessageLabel, boxMessageLabel;
    private JTextField nameTextField, hourTextField, rateTextField;
    private JPanel inputPanel, buttonPanel, outputPanel, inputPanel1, inputPanel2, inputPanel3, inputPanel4;
    private JComboBox<String> departmentBox;
    private JButton addButton, displayButton, exitButton;
    private JTable resultTable;
    private String[] columnNames = {"Employee name", "Department", "Weekly Salary"};
    private Object[][] data;
    private int WINDOW_WIDTH = 400;
    private int WINDOW_HEIGHT = 500;

    ArrayList<String> name = new ArrayList<String>();
    ArrayList<String> hour = new ArrayList<String>();
    ArrayList<String> rate = new ArrayList<String>();
    ArrayList<String> department = new ArrayList<String>();
    ArrayList<String> salary = new ArrayList<String>();

    private String[] departments = {"IT", "Marketing", "Human Resource", "Sales", "Customer Service", "Financial"};

    /*default constructor*/
    public PayrollFrame()
    {
        super("Payroll");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
        setLayout(new GridLayout(3,1));
        buildInputPanel();
        buildButtonPanel();
        buildOutputPanel();

        add(inputPanel);
        add(buttonPanel);
        add(outputPanel);

        setVisible(true);
    }

    private void buildInputPanel()
    {
        nameMessageLabel = new JLabel("Employee Name: ");
        hourMessageLabel = new JLabel("Work Hour: ");
        rateMessageLabel = new JLabel("Hourly Rate: ");
        boxMessageLabel = new JLabel("Department: ");
        nameTextField = new JTextField(10);
        hourTextField = new JTextField(10);
        rateTextField = new JTextField(10);
        departmentBox = new JComboBox<String>(departments);

        inputPanel = new JPanel();
        inputPanel1 = new JPanel();
        inputPanel2 = new JPanel();
        inputPanel3 = new JPanel();
        inputPanel4 = new JPanel();

        inputPanel1.add(nameMessageLabel);
        inputPanel1.add(nameTextField);
        inputPanel2.add(hourMessageLabel);
        inputPanel2.add(hourTextField);
        inputPanel3.add(rateMessageLabel);
        inputPanel3.add(rateTextField);
        inputPanel4.add(boxMessageLabel);
        inputPanel4.add(departmentBox);

        inputPanel.add(inputPanel1);
        inputPanel.add(inputPanel2);
        inputPanel.add(inputPanel3);
        inputPanel.add(inputPanel4);
    }

    private void buildButtonPanel() 
    {
        addButton = new JButton("Add More");
        addButton.addActionListener(new ButtonAction());
        displayButton = new JButton("Display Result");
        displayButton.addActionListener(new ButtonAction());
        exitButton = new JButton("Exit");
        exitButton.addActionListener(new ButtonAction());

        buttonPanel = new JPanel();

        buttonPanel.add(addButton);
        buttonPanel.add(displayButton);
        buttonPanel.add(exitButton);
    }

    private void buildOutputPanel()
    {
        outputPanel = new JPanel();
    }

    /*Copy ArrayList into 2D array to display in JTable format*/
    private void printData() 
    {
        for(int i=0; i<name.size(); i++)
        {
            data[i][0]=name.get(i);
            data[i][2]=department.get(i);
            data[i][2]=salary.get(i);
        }
        resultTable = new JTable(data, columnNames);
        outputPanel = new JPanel();
        outputPanel.add(resultTable);
    }

    /*Function of 3 buttons*/
    private class ButtonAction implements ActionListener
    {
        @Override
        public void actionPerformed(ActionEvent e) 
        {
            if(e.getActionCommand()=="Add More")
            {
                name.add(nameTextField.getText());
                hour.add(hourTextField.getText());
                rate.add(rateTextField.getText());
                department.add((String) departmentBox.getSelectedItem());
                calculateSalary(hourTextField.getText(), rateTextField.getText());
                nameTextField.setText("");
                hourTextField.setText("");
                rateTextField.setText("");
            }
            else if(e.getActionCommand()=="Display Result")
            {

                printData();

            }
            else if(e.getActionCommand()=="Exit")
            {
                System.exit(0);
            }
        }

        /*Calculate the weekly salary*/
        private void calculateSalary(String hourString, String rateString) 
        {
            int tempHour = Integer.parseInt(hourString);
            double tempRate = Double.parseDouble(rateString);
            if(tempHour<=40)
            {
                salary.add(Double.toString(tempHour * tempRate));
            }
            else
            {
                salary.add(Double.toString(40 * tempRate + (tempHour - 40) * (tempRate * 1.5))); //all hour after 40 will pay 1.5
            }
        }
    }
}

Answer 1

让我们从...开始......

if (e.getActionCommand() == "Add More") {

不是你在Java中比较String的方式，你需要使用equals方法，比如......

if ("Add More".equals(e.getActionCommand())) {

例如

接下来你做...

add(inputPanel);
add(buttonPanel);
add(outputPanel);

当使用BorderLayout时，将每个组件添加到BorderLayout中的默认位置，您需要为每个组件提供位置约束，否则会发生奇怪的事情，例如...

add(inputPanel, BorderLayout.NORTH);
add(buttonPanel, BorderLayout.CENTER);
add(outputPanel, BorderLayout.SOUTH);

<击>

我刚才意识到你正在使用GridLayout，我个人认为你会从BorderLayout获得更好的结果，但那就是我

然后你创建了resultTable和outputPanel的新实例，但是你永远不会将outputPanel添加到任何内容......

/*Copy ArrayList into 2D array to display in JTable format*/
private void printData() 
{
    for(int i=0; i<name.size(); i++)
    {
        data[i][0]=name.get(i);
        data[i][1]=department.get(i);
        data[i][2]=salary.get(i);
    }
    resultTable = new JTable(data, columnNames);
    outputPanel = new JPanel();
    outputPanel.add(resultTable);
}

更好的想法是创建resultTable，换入JScrollPane并将其添加到您的屏幕。

如果您要“打印”数据，请创建一个新的TableModel并将其应用于JTable

例如......

private void buildOutputPanel() {
    outputPanel = new JPanel(new BorderLayout());
    resultTable = new JTable();
    outputPanel.add(new JScrollPane(resultTable));
}

/*Copy ArrayList into 2D array to display in JTable format*/
private void printData() {
    for (int i = 0; i < name.size(); i++) {
        data[i][0] = name.get(i);
        data[i][2] = department.get(i);
        data[i][2] = salary.get(i);
    }
    DefaultTableModel model = new DefaultTableModel(data, columnNames);
    resultTable.setModel(model);
}

请查看How to Use Tables和How to Use Scroll Panes了解详情

示例

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableModel;

public class PayrollFrame extends JFrame {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                PayrollFrame frame = new PayrollFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    private JLabel nameMessageLabel, hourMessageLabel, rateMessageLabel, boxMessageLabel;
    private JTextField nameTextField, hourTextField, rateTextField;
    private JPanel inputPanel, buttonPanel, outputPanel, inputPanel1, inputPanel2, inputPanel3, inputPanel4;
    private JComboBox<String> departmentBox;
    private JButton addButton, displayButton, exitButton;
    private JTable resultTable;
    private String[] columnNames = {"Employee name", "Department", "Weekly Salary"};
    private Object[][] data;
    private int WINDOW_WIDTH = 400;
    private int WINDOW_HEIGHT = 500;

    ArrayList<String> name = new ArrayList<String>();
    ArrayList<String> hour = new ArrayList<String>();
    ArrayList<String> rate = new ArrayList<String>();
    ArrayList<String> department = new ArrayList<String>();
    ArrayList<String> salary = new ArrayList<String>();

    private String[] departments = {"IT", "Marketing", "Human Resource", "Sales", "Customer Service", "Financial"};

    /*default constructor*/
    public PayrollFrame() {
        super("Payroll");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());
        buildInputPanel();
        buildButtonPanel();
        buildOutputPanel();

        add(inputPanel, BorderLayout.NORTH);
        add(buttonPanel);
        add(outputPanel, BorderLayout.SOUTH);

        setVisible(true);
    }

    private void buildInputPanel() {
        nameMessageLabel = new JLabel("Employee Name: ");
        hourMessageLabel = new JLabel("Work Hour: ");
        rateMessageLabel = new JLabel("Hourly Rate: ");
        boxMessageLabel = new JLabel("Department: ");
        nameTextField = new JTextField(10);
        hourTextField = new JTextField(10);
        rateTextField = new JTextField(10);
        departmentBox = new JComboBox<String>(departments);

        inputPanel = new JPanel();
        inputPanel1 = new JPanel();
        inputPanel2 = new JPanel();
        inputPanel3 = new JPanel();
        inputPanel4 = new JPanel();

        inputPanel1.add(nameMessageLabel);
        inputPanel1.add(nameTextField);
        inputPanel2.add(hourMessageLabel);
        inputPanel2.add(hourTextField);
        inputPanel3.add(rateMessageLabel);
        inputPanel3.add(rateTextField);
        inputPanel4.add(boxMessageLabel);
        inputPanel4.add(departmentBox);

        inputPanel.add(inputPanel1);
        inputPanel.add(inputPanel2);
        inputPanel.add(inputPanel3);
        inputPanel.add(inputPanel4);
    }

    private void buildButtonPanel() {
        addButton = new JButton("Add More");
        addButton.addActionListener(new ButtonAction());
        displayButton = new JButton("Display Result");
        displayButton.addActionListener(new ButtonAction());
        exitButton = new JButton("Exit");
        exitButton.addActionListener(new ButtonAction());

        buttonPanel = new JPanel();

        buttonPanel.add(addButton);
        buttonPanel.add(displayButton);
        buttonPanel.add(exitButton);
    }

    private void buildOutputPanel() {
        outputPanel = new JPanel(new BorderLayout());
        resultTable = new JTable();
        outputPanel.add(new JScrollPane(resultTable));      
    }

    /*Copy ArrayList into 2D array to display in JTable format*/
    private void printData() {
        for (int i = 0; i < name.size(); i++) {
            data[i][0] = name.get(i);
            data[i][2] = department.get(i);
            data[i][2] = salary.get(i);
        }
        TableModel model = new DefaultTableModel(data, columnNames);
        resultTable.setModel(model);
    }

    /*Function of 3 buttons*/
    private class ButtonAction implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            if ("Add More".equals(e.getActionCommand())) {
                name.add(nameTextField.getText());
                hour.add(hourTextField.getText());
                rate.add(rateTextField.getText());
                department.add((String) departmentBox.getSelectedItem());
                calculateSalary(hourTextField.getText(), rateTextField.getText());
                nameTextField.setText("");
                hourTextField.setText("");
                rateTextField.setText("");
            } else if ("Display Result".equals(e.getActionCommand())) {

                printData();

            } else if ("Exit".equals(e.getActionCommand())) {
                System.exit(0);
            }
        }

        /*Calculate the weekly salary*/
        private void calculateSalary(String hourString, String rateString) {
            int tempHour = Integer.parseInt(hourString);
            double tempRate = Double.parseDouble(rateString);
            if (tempHour <= 40) {
                salary.add(Double.toString(tempHour * tempRate));
            } else {
                salary.add(Double.toString(40 * tempRate + (tempHour - 40) * (tempRate * 1.5))); //all hour after 40 will pay 1.5
            }
        }
    }
}

Answer 2

感谢@MadProgrammer的帮助！他的回复帮助我解决了我遇到的许多问题，并且真的试图向我解释一些事情。在咨询了我的讲师后，我通过编辑printData方法成功编译并运行了我的程序。

private void printData() 
    {
        DefaultTableModel model = new DefaultTableModel(columnNames,name.size());
        resultTable.setModel(model);  
        for(int i=0; i<name.size(); i++)
        {
            resultTable.setValueAt(name.get(i),i,0);
            resultTable.setValueAt(department.get(i),i,1);
            resultTable.setValueAt(salary.get(i),i,2);
        }
    }