How to adjust the grid size after resizing the frame?

I was wondering the following: I have a MainWindow component (which contains a frame (JFrame)) and sever开发者_开发技巧al other JPanels. Where one JPanel, let's say gridPanel uses the gridLayout as LayoutManager. Now my problem is that I want to adjust (set the size of rows / set the size of columns) after the window has been resized. Can someone tell me how I can achieve actions that can be triggered after resizing the frame as I am not familiar with the listeners involved.

It should be the done on the most "standard" coding practices. Thank you for your response and answers!

If you want your grid to "fill up" a container, or fill up the JFrame, then key is to use proper layout managers to hold the GridLayout-using container. For instance if you add the GridLayout-using container to another container that uses FlowLayout, then the GridLayout-using container will not change size if its holding container changes size. However if you add the GridLayout-using container to another container that uses BorderLayout and to its BorderLayout.CENTER position, then the GridLayout-using container will resize as the BorderLayout-using parent container resizes.

Example:

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

@SuppressWarnings("serial")
public class ExpandingGrid extends JPanel {
   private static final int GAP = 5;

   public ExpandingGrid() {

      // create a BorderLayout-using JPanel
      JPanel borderLayoutPanel = new JPanel(new BorderLayout());
      borderLayoutPanel.setBorder(BorderFactory.createTitledBorder("BorderLayout Panel"));
      borderLayoutPanel.add(createGridPanel(), BorderLayout.CENTER); // add a Grid to it

      // create a FlowLayout-using JPanel
      JPanel flowLayoutPanel = new JPanel(new FlowLayout());
      flowLayoutPanel.setBorder(BorderFactory.createTitledBorder("FlowLayout Panel"));
      flowLayoutPanel.add(createGridPanel()); // add a grid to it

      // set up the main JPanel 
      setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
      setLayout(new GridLayout(1, 0, GAP, 0)); // grid with 1 row
      // and add the borderlayout and flowlayout using JPanels to it
      add(borderLayoutPanel);
      add(flowLayoutPanel);
   }

   // create a JPanel that holds a bunch of JLabels in a GridLayout
   private JPanel createGridPanel() {
      int rows = 5;
      int cols = 5;
      JPanel gridPanel = new JPanel(new GridLayout(rows, cols));
      for (int i = 0; i < rows; i++) {
         for (int j = 0; j < cols; j++) {
            // create the JLabel that simply shows the row and column number
            JLabel label = new JLabel(String.format("[%d, %d]", i, j),
                     SwingConstants.CENTER);
            // give the JLabel a border
            label.setBorder(BorderFactory.createEtchedBorder());
            gridPanel.add(label); // add to the GridLayout using JPanel
         }
      }
      return gridPanel;
   }

   private static void createAndShowUI() {
      JFrame frame = new JFrame("ExpandingGrid");
      frame.getContentPane().add(new ExpandingGrid());
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

Also, if this is not helpful, then you may wish to elaborate more on your problem and post code, preferably an SSCCE.

That's why I wanted to only adjust the columns.

Maybe the Wrap Layout is what you are looking for.