Java GUI 组件和面板对齐

Question

我对 Java GUI 很陌生，在调整我创建的这个程序的 GUI 时遇到了麻烦。代码如下:

代码:

import javax.swing.*;
import java.awt.*;
import javax.swing.table.DefaultTableModel;
public class SalesScreen{

private JPanel mainPanel = new JPanel();

//Top Member Panel
private JPanel memberPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
private JLabel memberID =  new JLabel();
private JTextField memberIDField = new JTextField(10);
private JLabel memberName = new JLabel();
private JTextField memberNameField = new JTextField(30);
private JButton memberButton = new JButton("OK");

//Center Table Panel
private JPanel tablePanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
private JTable itemList;
String [] columnNames = {"Barcode" , "Name" , "Price (RM)" , "Quantity"};
int numRows = 30;
DefaultTableModel model = new DefaultTableModel(numRows , columnNames.length);
JScrollPane scroll;

//Bottom Right 
private JPanel infoPanel = new JPanel(new BorderLayout());
private JPanel infoGridPanel = new JPanel( new GridLayout(4,2));
private JPanel infoFlowPanel = new JPanel(new FlowLayout());
private JLabel total = new JLabel("          Total (RM) :");
private JLabel discount = new JLabel("          Discount Rate (%) : ");
private JLabel overall = new JLabel("          Overall (RM) :");
private JLabel payment = new JLabel("          Payment (RM) :");
private JButton process = new JButton("PROCESS");
private JTextField totalPrice = new JTextField(5);
private JTextField discountRate = new JTextField(5);
private JTextField overallPrice = new JTextField(5);
private JTextField paymentMade = new JTextField(5);

//Bottom
private JPanel itemPanel = new JPanel(new BorderLayout());
private JPanel testPanel = new JPanel(new GridLayout(2 , 4 , 4 , 20));
private JLabel emptyLabel = new JLabel("");
private JLabel emptyLabel2 = new JLabel("");
private JLabel barcode = new JLabel("Enter Barcode :");
private JTextField barcodeScanner = new JTextField(5);
private JLabel quantity = new JLabel("Quantity :");
private JTextField itemQuantity = new JTextField(5);
private JButton addItem = new JButton("Add");
private JButton deleteItem = new JButton("Delete");

    //                                           //
   //                                           //
  //    Beginning of Constructor and Method    //
 //                                           //
//                                           //

SalesScreen(JTabbedPane tabp , JFrame f) //tabp is Jtabbedpanel , f is the Jframe
{
    mainPanel.setLayout(new BorderLayout());
    memberID.setText("          Member ID :");
    memberIDField.setText("");
    memberName.setText("Member Name :");
    memberNameField.setText("");
    memberNameField.setEditable(false);
    memberPanel.add(memberID);
    memberPanel.add(memberIDField);
    memberPanel.add(memberName);
    memberPanel.add(memberNameField);
    memberPanel.add(memberButton);
    //
    model.setColumnIdentifiers(columnNames);
    itemList = new JTable(model);
    scroll = new JScrollPane(itemList); 
    //tablePanel.add(scroll);
    //
    total.setLabelFor(totalPrice);
    totalPrice.setEditable(false);
    discountRate.setEditable(false);
    overallPrice.setEditable(false);
    process.setPreferredSize(new Dimension(100, 100));
    discount.setLabelFor(discountRate);
    overall.setLabelFor(overallPrice);
    payment.setLabelFor(paymentMade);
    infoGridPanel.add(total);
    infoGridPanel.add(totalPrice);
    infoGridPanel.add(discount);
    infoGridPanel.add(discountRate);
    infoGridPanel.add(overall);
    infoGridPanel.add(overallPrice);
    infoGridPanel.add(payment);
    infoGridPanel.add(paymentMade);
    infoFlowPanel.add(infoGridPanel);
    infoFlowPanel.add(process);
    infoPanel.add(infoFlowPanel , "South");
    //

    testPanel.setMaximumSize( new Dimension(  100, 100) );
    testPanel.add(barcode);
    testPanel.add(barcodeScanner);
    testPanel.add(addItem);
    testPanel.add(deleteItem);
    testPanel.add(quantity);
    testPanel.add(itemQuantity);
    testPanel.add(emptyLabel);
    testPanel.add(emptyLabel2);
    itemPanel.add(testPanel , "West");
    //
    mainPanel.add(memberPanel , "North");
    mainPanel.add(scroll , "Center");
    mainPanel.add(infoPanel , "East");
    mainPanel.add(itemPanel , "South");
    tabp.add("Sales" , mainPanel); 
    f.add(tabp);
}

}

问题:

1.)正如你所看到的，中间会有一个Jtable，右下面板有一个JPanel，底部也有一个。我想要做的是通过将底部面板稍微移到上方来消除 Jtable 末尾的可用空间。我不断地尝试却没有结果。

Answer 1

如果您希望稍微向上移动底部面板，只需减小 testPanel 的 GridLayout 中的垂直间隙即可。替换

private JPanel testPanel = new JPanel(new GridLayout(2 , 4 , 4 , 20));

与

private JPanel testPanel = new JPanel(new GridLayout(2, 4, 4, 5));

最好重写组件的 getPreferredSize() 而不是调用 setPreferredSize。这可确保首选大小无法由其他组件设置。

调用 JFrame.pack 将通过根据首选大小排列所有组件来调整窗口大小来完成任务。