我正在尝试让JScrollPane出现在我的JTable上。当我创建组件的实例时，我将表传递给了滚动窗格。但无济于事还没有显示在我的桌子上。
table = new JTable();
scrollPane = new JScrollPane(table);
table.setPreferredSize(new Dimension(200,100));
我不知道如何解决这个问题，我似乎无法找到导致它失败的问题。这是GUI代码的其余部分。这很长。将jtable添加到jpanel从第152行开始。
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*/
package javasql;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.awt.event.ActionEvent;
import javax.swing.table.DefaultTableModel;
/**
*
* @author KJ4CC
*/
public class UserInterface implements ActionListener {
DefaultTableModel dtm = new DefaultTableModel(0, 0);
public UserInterface() {
startGui();
}
JFrame frame = new JFrame();
Javasql sql = new Javasql();
JPanel buttom = new JPanel(new GridBagLayout());
JPanel commandPane = new JPanel(new GridBagLayout());
JPanel top = new JPanel(new GridBagLayout());
JPanel buttons = new JPanel(new GridBagLayout());
JPanel label = new JPanel(new GridBagLayout());
JButton connect = new JButton("Connect To Database");
JButton clr = new JButton("Clear Command");
JButton exeSql = new JButton("Execute SQL Command");
JButton clrRes = new JButton("Clear Result Window");
JLabel infoLabel = new JLabel("Enter Database Information ");
JLabel driverLabel = new JLabel("JDBC Driver: ");
JLabel dbLabel = new JLabel("Database URL: ");
JLabel userLabel = new JLabel("Username: ");
JLabel passLabel = new JLabel("Password: ");
JLabel sqlLabel = new JLabel("Enter SQL Command: ");
JLabel connectionLabel = new JLabel("No Connection Now ");
JLabel exeLabel = new JLabel("SQL Execution Result: ");
//creating an instance of the new table
public JTable table;
public JScrollPane scrollPane;
JComboBox driverSelect = new JComboBox();
JComboBox url = new JComboBox();
JTextField username = new JTextField();
JTextField pass = new JTextField();
JTextArea command = new JTextArea(1, 1);
public void startGui() {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GridBagConstraints c = new GridBagConstraints();
System.out.println("sdf");
c.insets = new Insets(0, 0, 0, 10);
c.fill = 0;
c.weightx = 1;
//adding all of the compoenets to their panel and then to the frame.
c.gridx = 0;
c.gridy = 0;
c.fill = GridBagConstraints.HORIZONTAL;
top.add(infoLabel, c);
c.gridx = 0;
c.gridy = 1;
top.add(driverLabel, c);
c.gridx = 1;
c.gridy = 1;
c.ipadx = 150;
c.fill = GridBagConstraints.HORIZONTAL;
top.add(driverSelect, c);
c.gridx = 0;
c.gridy = 2;
c.fill = 0;
top.add(dbLabel, c);
c.gridx = 1;
c.gridy = 2;
c.fill = GridBagConstraints.HORIZONTAL;
top.add(url, c);
c.gridx = 0;
c.gridy = 3;
c.fill = 0;
c.fill = 0;
top.add(userLabel, c);
c.gridx = 1;
c.gridy = 3;
c.fill = GridBagConstraints.HORIZONTAL;
top.add(username, c);
c.gridx = 0;
c.gridy = 4;
c.fill = 0;
c.fill = 0;
top.add(passLabel, c);
c.gridx = 1;
c.gridy = 4;
c.fill = GridBagConstraints.HORIZONTAL;
top.add(pass, c);
//add the driver and url to the comboboxes
c.gridx = 2;
c.gridy = 0;
commandPane.add(sqlLabel, c);
c.gridx = 2;
c.gridy = 1;
c.ipadx = 150;
c.ipady = 75; //sql text area for command
c.fill = GridBagConstraints.FIRST_LINE_END;
c.fill = GridBagConstraints.HORIZONTAL;
commandPane.add(command, c);
c.insets = new Insets(0, 0, 0, 20);
c.ipadx = 9;
c.ipady = 1;
c.gridx = 0;
c.gridy = 0;
//buttons
label.add(connectionLabel, c);
c.gridx = 1;
c.gridy = 0;
//c.insets = new Insets(0, 0, 0, 50);
buttons.add(connect, c);
connect.addActionListener(this);
c.gridx = 2;
buttons.add(clr, c);
clr.addActionListener(this);
c.gridx = 3;
buttons.add(exeSql, c);
exeSql.addActionListener(this);
//adding the label and buttons above and below the tabel.
c.gridx = 0;
c.gridy = 1;
buttom.add(exeLabel, c);
c.gridx = 0;
c.gridy = 2;
//-----------------------------------------------------------------Table here
table = new JTable();
scrollPane = new JScrollPane(table);
table.setPreferredSize(new Dimension(200, 100));
c.fill = GridBagConstraints.HORIZONTAL;
buttom.add(table, c);
buttom.add(scrollPane);
c.gridx = 0;
c.gridy = 3;
buttom.add(clrRes, c);
c.weightx = 2;
c.weighty = 2;
c.gridx = 0;
c.gridy = 0;
frame.setLayout(new GridLayout(3, 2));
frame.add(top);
c.gridx = 2;
c.gridy = 1;
frame.add(commandPane);
frame.add(label);
frame.add(buttons);
frame.add(buttom, BorderLayout.SOUTH);
//adding the content panel to the jframe.
frame.pack();
frame.setSize(1000, 550);
frame.setVisible(true);
//adding items to both of the combo boxes.
driverSelect.addItem("com.mysql.jdbc.Driver");
url.addItem("jdbc:mysql://localhost:3306/project3");
}
public void actionPerformed(ActionEvent e) {
if (e.getSource() == connect) {
sql.connect(this);
} else if (e.getSource() == clr) {
command.setText("");
} else if (e.getSource() == exeSql) {
sql.exeCommand(this);
}
}
}
答案 0 :(得分：2)
scrollPane = new JScrollPane(table);
table.setPreferredSize(new Dimension(200, 100));
c.fill = GridBagConstraints.HORIZONTAL;
buttom.add(table, c);
buttom.add(scrollPane);
这里你把表添加两次，直接在第一行和（隐式）以及最后一行的ScrollPane。
在Swing中，这是不可能的。因此，当您将JTable直接添加到bottom面板时，将从第一行的Scrollpane中删除JTable，然后在最后一行添加空滚动窗格，删除之前添加的JTable。
只需删除第一行。
答案 1 :(得分：2)
您无法将表格添加两次：
table = new JTable();
scrollPane = new JScrollPane(table); //here
table.setPreferredSize(new Dimension(200, 100));
c.fill = GridBagConstraints.HORIZONTAL;
buttom.add(table, c); //here
buttom.add(scrollPane);
如果将其添加到scrollPane，只需添加滚动窗格。组件不能有两个父母。
我没有检查您的完整代码，但请尝试
buttom.add(scrollPane,c);
而不是
buttom.add(table, c); //here
buttom.add(scrollPane);