JTable未显示.我如何解决它

Question

图像

在我附加的图片（链接）中，应该在向前，向后和删除带有JTable标头的按钮下显示JTable：x/y/y/width/height

但是，不是。谁能帮帮我吗？我在这里做错了什么？

import java.awt.BorderLayout;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;
public class Whiteboard extends JFrame {
    public static void main(String[] args) {
        new Whiteboard();
    }
    private static final long serialVersionUID = 1L;
    private String[] petStrings = { "Bird", "Cat", "Dog", "Rabbit", "Pig" };
    public Whiteboard() {
        JButton setColor = new JButton("Color");
        JPanel colorPanel = new JPanel();
        colorPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        colorPanel.setLayout(new BoxLayout(colorPanel, BoxLayout.X_AXIS));
        colorPanel.add(setColor);
        JButton addRect = new JButton("Rect");
        JButton addOval = new JButton("Oval");
        JButton addLine = new JButton("Line");
        JButton addText = new JButton("Text");
        JPanel addPanel = new JPanel();
        addPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        addPanel.setLayout(new BoxLayout(addPanel, BoxLayout.X_AXIS));
        addPanel.add(addRect);
        addPanel.add(addOval);
        addPanel.add(addLine);
        addPanel.add(addText);
        JTextField setText = new JTextField("");
        JComboBox<String> changeFont = new JComboBox<String>(petStrings);
        JPanel textPanel = new JPanel();
        textPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        textPanel.setLayout(new BoxLayout(textPanel, BoxLayout.X_AXIS));
        textPanel.add(setText);
        textPanel.add(changeFont);
        JButton sendForward = new JButton("Forward");
        JButton sendBackward = new JButton("Backward");
        JButton removeObj = new JButton("Remove");
        JPanel orderPanel = new JPanel();
        orderPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        orderPanel.setLayout(new BoxLayout(orderPanel, BoxLayout.X_AXIS));
        orderPanel.add(sendForward);
        orderPanel.add(sendBackward);
        orderPanel.add(removeObj);
        DefaultTableModel tableModel = new DefaultTableModel(new String[] { "X", "Y", "Width", "Height" }, 0);
        JTable infoTable = new JTable(tableModel);
        JScrollPane tablePanel = new JScrollPane();
        infoTable.setPreferredScrollableViewportSize(infoTable.getPreferredSize());
        infoTable.setFillsViewportHeight(true);
        tablePanel.add(infoTable);
        tableModel.addRow(new String[] { "TEST1", "TEST2", "TEST3", "TEST4" });
        JPanel control = new JPanel();
        control.setLayout(new BoxLayout(control, BoxLayout.Y_AXIS));
        control.add(colorPanel);
        control.add(addPanel);
        control.add(textPanel);
        control.add(orderPanel);
        control.add(tablePanel);
        Canvas canvas = new Canvas();
        canvas.setLayout(new BoxLayout(canvas, BoxLayout.PAGE_AXIS));
        JPanel window = new JPanel();
        window.add(control);
        window.add(canvas);
        getContentPane().add(window);
        pack();
        setLocationRelativeTo(null);
        setTitle("Whiteboard");
        setLayout(new BorderLayout());
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

Answer 1

tablePanel.add(infoTable);

不要将组件直接添加到JScrollPane。该组件应添加到滚动面板的JViewport中。

您可以使用：

JScrollPane tablePanel = new JScrollPane(infoTable); // easiest way, 

或

tablePanel.getViewport().setViewportView( infoTable );

另外，不要使用Canvas类。那是一个AWT组件。您应该使用JPanel。