Java：AbsoluteLayout中的额外空间

Question

Is it possible to have some extra space around the edges of a JFrame that uses AbsoluteLayout? When I have a button as the downwardsmost component on the JFrame, it gets positioned right up against the bottom edge of the JFrame window, and it looks bad. I would like to know if there's a way to add a little extra space between components and the edge of the JFrame while using AbsoluteLayout.

Answer 1

Suggestions:

• When you add a component to a JFrame, you're actually adding it to the JFrame's contentPane. To give the contentPane a "buffer" border, consider giving it an EmptyBorder(...) with the parameters being int constants for the amount of border desired around the component.
• Avoid using "absolute" layouts for anything, and especially for placing components at easy to place locations for the layout managers, such as at the bottom of the GUI.

For example, note in the GUI created in the code below how the center and bottom JPanel's don't go out to the edge of the GUI because of the empty border:

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.*;

public class ButtonAtBottom {
   private static void createAndShowGui() {
      JPanel bottomPanel = new JPanel();
      bottomPanel.add(new JButton("Bottom Button"));
      bottomPanel.setBorder(BorderFactory.createTitledBorder("Bottom Panel"));

      JPanel centerPanel = new JPanel();
      centerPanel.setBorder(BorderFactory.createTitledBorder("Center Panel"));


      JPanel mainPanel = new JPanel(new BorderLayout());
      mainPanel.add(centerPanel, BorderLayout.CENTER);
      mainPanel.add(bottomPanel, BorderLayout.PAGE_END);

      // **** here I add the border to the mainPanel which I'll 
      // make into the contentPane
      int eb = 25;
      mainPanel.setBorder(BorderFactory.createEmptyBorder(eb, eb, eb, eb));

      // don't set the preferredSize per Kleopatra, but am doing it
      // here simply to make code shorter for this sscce
      mainPanel.setPreferredSize(new Dimension(500, 400));

      JFrame frame = new JFrame("ButtonAtBottom");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setContentPane(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

Answer 2

您可以使用Box.createRigidArea（维度）创建一个可以在按钮下方添加的空白区域。

Answer 3

Set an empty border on your content panel where SIZE is the amount of padding you want.

JFrame frame = new JFrame();
JPanel panel = new JPanel(null);
panel.setBorder(BorderFactory.createEmptyBorder(SIZE,SIZE,SIZE,SIZE);
frame.setContentPane(panel); 
//The rest

The arguments are for top, left, bottom and right padding so if you want different paddings on each edge, you can set it accordingly.