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How to use VerticalGlue in box layout

I'm trying to build a simple panel which I will throw some fields onto and capture some user data. I typically use a combination of GridBagLayouts (thanks to trashgod) and BoxLayouts to achieve the layout I want. I normally don't have any issues with using them and they just do what makes intuitive sense 99% of the time, but I can't seem to make this rather simple panel function properly. Can anyone tell me why?
The panel class:
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class EmailPanel extends JPanel {
private JButton m_OkButton;
private JPanel m_MainPanel;
private JTextField m_ServerIPTF;
private JTextField m_ServerPortTF;
private JTextField m_DomainNameTF;
private JTextField m_UnitNameTF;
private JTextField m_Recipient1TF;
private JTextField m_Recipient2TF;
private final Dimension LARGE_TEXTFIELD_SIZE = new Dimension(125, 25);
public EmailPanel() {
init();
}
private void init() {
this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
JPanel tPanel;
JLabel tLabel;
Header: {
tPanel = new JPanel();
tPanel.setLayout(new BoxLayout(tPanel, BoxLayout.X_AXIS));
tPanel.add(Box.createHorizontalGlue());
tLabel = new JLabel("Email Settings");
tPanel.add(tLabel);
tPanel.add(Box.createHorizontalGlue());
tPanel.setBorder(BorderFactory.createMatteBorder(0, 0, 3, 0, Color.red));
this.add(tPanel);
}
MainPanel: {
m_MainPanel = new JPanel();
m_MainPanel.setLayout(new BoxLayout(m_MainPanel, BoxLayout.Y_AXIS));
m_MainPanel.add(Box.createVerticalStrut(5));
tPanel = new JPanel();
tPanel.setLayout(new BoxLayout(tPanel, BoxLayout.X_AXIS));
tPanel.add(Box.createHorizontalStrut(3));
tLabel = new JLabel("Server IP Address:");
tPanel.add(tLabel);
tPanel.add(Box.createHorizontalStrut(3));
m_ServerIPTF = new JTextField();
m_ServerIPTF.setMinimumSize(LARGE_TEXTFIELD_SIZE);
m_ServerIPTF.setMaximumSize(LARGE_TEXTFIELD_SIZE);
m_ServerIPTF.setPreferredSize(LARGE_TEXTFIELD_SIZE);
tPanel.add(m_ServerIPTF);
tPanel.add(Box.createHorizontalStrut(25));
tLabel = new JLabel("Server Port");
tPanel.add(tLabel);
tPanel.add(Box.createHorizontalStrut(3));
m_ServerPortTF = new JTextField();
m_ServerPortTF.setMinimumSize(LARGE_TEXTFIELD_SIZE);
m_ServerPortTF.setMaximumSize(LARGE_TEXTFIELD_SIZE);
m_ServerPortTF.setPreferredSize(LARGE_TEXTFIELD_SIZE);
tPanel.add(m_ServerPortTF);
tPanel.add(Box.createHorizontalGlue());
m_MainPanel.add(tPanel);
m_MainPanel.add(Box.createVerticalStrut(5));
tPanel = new JPanel();
tPanel.setLayout(new BoxLayout(tPanel, BoxLayout.X_AXIS));
tPanel.add(Box.createHorizontalStrut(6));
tLabel = new JLabel("Domain Name:");
tPanel.add(tLabel);
tPanel.add(Box.createHorizontalStrut(3));
m_DomainNameTF = new JTextField();
m_DomainNameTF.setMinimumSize(LARGE_TEXTFIELD_SIZE);
m_DomainNameTF.setMaximumSize(LARGE_TEXTFIELD_SIZE);
m_DomainNameTF.setPreferredSize(LARGE_TEXTFIELD_SIZE);
tPanel.add(m_DomainNameTF);
tPanel.add(Box.createHorizontalGlue());
m_MainPanel.add(tPanel);
this.add(m_MainPanel);
}
OKButton: {
m_OkButton = new JButton("Ok");
tPanel = new JPanel();
tPanel.setLayout(new BoxLayout(tPanel, BoxLayout.X_AXIS));
tPanel.add(Box.createHorizontalGlue());
tPanel.add(m_OkButton);
tPanel.add(Box.createHorizontalGlue());
this.add(tPanel);
}
this.add(Box.createVerticalGlue());
}
}
If you add this to / use this as a content pane, you will see that there are large gaps on the Y axis between the various controls. I'm under the impression that the vertical glue that I add at the end of the init method should grow to consume all the space below the OK button, and the controls would be pushed together as a consequence. What I'm seeing is that it seems to be splitting up the space evenly between the various instances of my temporary JPanel object tPanel and the vertical glue at the bottom. How do I make it stop doing that?
Edit: It seems that the behavior is the same both with and without the somewhat superfluous m_MainPanel object.
This is what I see when it renders and the form is made larger than needed for the controls. I would expect the vertical glue to fill the space below the OK button to keep the controls on the top of the form.

I copy-pasted your code and added the main method:
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.getContentPane().add(new EmailPanel());
frame.pack();
frame.setVisible(true);
}
This is the result:
with or without the line this.add(Box.createVerticalGlue());
Is this what you wanted or not?
Edit: Solution
I edited your code to achieve the desired result:
public class EmailPanel extends JPanel {
private JButton okButton;
private JTextField serverIPTF;
private JTextField serverPortTF;
private JTextField domainNameTF;
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.getContentPane().add(new EmailPanel());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setMinimumSize(frame.getPreferredSize());
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public EmailPanel() {
init();
}
private void init() {
setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
JPanel tPanel;
JLabel tLabel;
// Header
tLabel = new JLabel("Email Settings", JLabel.CENTER);
tLabel.setAlignmentX(CENTER_ALIGNMENT);
tLabel.setMaximumSize(new Dimension(Integer.MAX_VALUE, tLabel.getPreferredSize().height));
tLabel.setBorder(BorderFactory.createMatteBorder(0, 0, 3, 0, Color.red));
add(tLabel);
// Fields
JPanel fieldsPanel = new JPanel();
fieldsPanel.setLayout(new BoxLayout(fieldsPanel, BoxLayout.Y_AXIS));
fieldsPanel.setBorder(BorderFactory.createMatteBorder(5, 3, 5, 3, new Color(0, 0, 255, 255)));
// Top fields
serverIPTF = new JTextField(10);
serverIPTF.setMaximumSize(serverIPTF.getPreferredSize());
serverPortTF = new JTextField(10);
serverPortTF.setMaximumSize(serverPortTF.getPreferredSize());
tPanel = new JPanel();
tPanel.setLayout(new BoxLayout(tPanel, BoxLayout.X_AXIS));
tPanel.add(new JLabel("Server IP Address:"));
tPanel.add(Box.createRigidArea(new Dimension(3, 0)));
tPanel.add(serverIPTF);
tPanel.add(Box.createRigidArea(new Dimension(25, 0)));
tPanel.add(new JLabel("Server Port"));
tPanel.add(Box.createRigidArea(new Dimension(3, 0)));
tPanel.add(serverPortTF);
tPanel.add(Box.createHorizontalGlue());
fieldsPanel.add(tPanel);
fieldsPanel.add(Box.createRigidArea(new Dimension(0, 5)));
// Lower field
domainNameTF = new JTextField(10);
domainNameTF.setMaximumSize(domainNameTF.getPreferredSize());
tPanel = new JPanel();
tPanel.setLayout(new BoxLayout(tPanel, BoxLayout.X_AXIS));
tPanel.add(new JLabel("Domain Name:"));
tPanel.add(Box.createRigidArea(new Dimension(3, 0)));
tPanel.add(domainNameTF);
tPanel.add(Box.createHorizontalGlue());
fieldsPanel.add(tPanel);
add(fieldsPanel);
// OK Button
okButton = new JButton("OK");
okButton.setAlignmentX(CENTER_ALIGNMENT);
add(okButton);
}
}
Explanation:
BoxLayout says:
When a BoxLayout lays out components from top to bottom, it tries to size each component at the component's preferred height. If the vertical space of the layout does not match the sum of the preferred heights, then BoxLayout tries to resize the components to fill the space. The components either grow or shrink to fill the space, with BoxLayout honoring the minimum and maximum sizes of each of the components. Any extra space appears at the bottom of the container.
(emphasis mine)
Which tells us that if we restrict the components' maximum height to their preferred height, all the extra vertical space will go to the bottom, just as you want. Hence, we added for all the text fields (the labels do not grow vertically) the line:
nameTF.setMaximumSize(nameTF.getPreferredSize());
and we don't need any vertical glue.
Notes:
I created the text fields with 10 columns, you can change this value.
The top label does not need horizontal glue to stretch it, just relax the maximum width constraint and set the alignment (similarly to the bottom button).
Instead of creating a lot of rigid areas (you used struts), I created a border with the appropriate widths. It is blue for visual purposes, but you should set its alpha to 0 to make is transparent.
Use createRigidArea instead of createXXXStrut (see the note in the above link).
I used frame.setMinimumSize(frame.getPreferredSize()) to not let the window resize to a smaller size than its contents. This is optional.
Non-final fields and variables should not use underscore (_) in the name according to Java naming conventions.
You did not specify horizontal stretching behavior, so it does whatever it does.
I still think that box layout is not the best approach here, or at least do not allow resizing of the window at all (so to not deal with extra space).

Border Layout Spacing/Margins

for my beginner Java class we made an automated Tic-Tac-Toe game, and now we are creating a GUI to play it on. However, I'm having a lot of trouble getting the spacing/margins right. So far, I've just been trying to get the general framework for the GUI, and then I'm going to go back and actually implement the Tic-Tac-Toe game I have already made. So, far, I have this:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class ITTTGUI extends JFrame implements ActionListener{
//butimport javax.swing.border.*;tons
private JPanel sizePanel;
private JPanel buttonPanel;
private JPanel displayPanel;
private JPanel bottomPanel;
private JTextField size;
private JButton rebuildButton;
private JButton[] buttons;
private JLabel output;
//constructor
public NumberChooser(){
setTitle("BitchFace");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//content pane
Container cp = getContentPane();
//add a panel for the size
sizePanel = new JPanel();
sizePanel.setBorder(new EmptyBorder(5, 5, 5, 5) );//adds margin to panel
sizePanel.setLayout(new FlowLayout());
size = new JTextField("3",5);
sizePanel.add(new JLabel("N"));
sizePanel.add(size);
rebuildButton = new JButton("Rebuild");
rebuildButton.addActionListener(this);
sizePanel.add(rebuildButton);
//add bottom panel for output
sizePanel.add(new JButton("Player:"), BorderLayout.EAST);
sizePanel.add(new JButton("Move:"), BorderLayout.EAST);
sizePanel.add(new JButton("Winner:"), BorderLayout.EAST);
//add a panel for the numbers
buttonPanel = new JPanel();
buttonPanel.setBorder(new EmptyBorder(5, 5, 5, 5) );//adds margin to panel
buildButtonsPanel();
//add bottom panel for output
JPanel bottomPanel = new JPanel();
bottomPanel.setBorder(new EmptyBorder(5, 5, 5, 5) );//adds margin to panel
bottomPanel.add(new JButton("New Game"), BorderLayout.SOUTH);
bottomPanel.add(new JButton("Advise"), BorderLayout.SOUTH);
bottomPanel.add(new JButton("Quit"), BorderLayout.SOUTH);
//add panels to main pane
cp.setLayout(new BorderLayout());
cp.add(sizePanel, BorderLayout.EAST);
cp.add(buttonPanel, BorderLayout.CENTER);
cp.add(bottomPanel, BorderLayout.SOUTH);
pack();
}
//this is a helper method to rebuild the buttons panel
private void buildButtonsPanel(){
int n = 3;
try{
n = Integer.parseInt(size.getText());
}catch(Exception e){
e.printStackTrace();
}
buttonPanel.removeAll();
buttonPanel.setLayout(new GridLayout(n,n,4,4));
buttons = new JButton[n*n];
for(int i=0; i < buttons.length; i++){
buttons[i] = new JButton("*");
buttonPanel.add(buttons[i]);
buttons[i].addActionListener(this);
}
revalidate();
repaint();
pack();
}
public void actionPerformed(ActionEvent e){
Object s = e.getSource();
//check to see if the action came from the rebuild button
if(s == rebuildButton){
buildButtonsPanel();
}
//otherwise it came from the grid
}
//entry point
public static void main(String[] args){
//create the GUI
NumberChooser nc = new NumberChooser();
nc.setVisible(true);
}
}
It doesn't have to be exact, just generally the same.
And also there is no X or winner variable since I haven't implemented that. I also tried changing the margins from (5,5,5,5) to like (1,1,1,1), but that didn't change anything at all so that also confused me.
Any help with this, or how to generally go about this assignment would be appreciated.
(And it's not accepting my images. Sorry.)
Links are:
The problem is that is looks like this:
https://i1224.photobucket.com/albums/ee362/Devolutor/COPimage1_zps459f304b.png
And it is supposed to look like this:
http://i1224.photobucket.com/albums/ee362/Devolutor/COPimage2_zps8981c846.png

To have more space between the buttons, use a number of pixels beiiger than 4 for the grid layout:
buttonPanel.setLayout(new GridLayout(n,n,4,4));
To have a grid rather than a flow at the right side, use a GridLayout (just like you did for your buttons, but with 4 rows and 2 columns) rather than a FlowLayout.

GUI not showing as intended

I'm trying to draw a gui like shown in the figure, but somehow I'm not able to place the objects in right place (I guess that the problem is with the layout) the textArea is suppose to go in the middle... but is not showing at all
package Chapter22Collections;
import javax.swing.*;
import java.awt.*;
public class Exercise226 extends JFrame {
private JButton jbSort;
private JButton jbReverse;
private JButton jbAdd;
private JButton jbShuffle;
private JLabel jlAddnum;
private JTextArea jTextDisplay;
private JTextField jTextAdd;
public Exercise226() {
jbSort = new JButton("Sort");
jbReverse = new JButton("Reverse");
jbShuffle = new JButton("Shuffle");
jbAdd = new JButton("Add");
jlAddnum = new JLabel("Add number here: ");
jTextDisplay = new JTextArea();
jTextAdd = new JTextField(8);
setLayout(new BorderLayout());
JPanel p1 = new JPanel(new GridLayout(1,3));
p1.add(jlAddnum);
p1.add(jTextAdd);
p1.add(jbAdd);
JPanel p2 = new JPanel(new GridLayout(1,3));
p2.add(jbSort);
p2.add(jbReverse);
p2.add(jbShuffle);
add(p1, BorderLayout.NORTH);
add(jTextDisplay, BorderLayout.CENTER);
add(p2, BorderLayout.SOUTH);
}
public static void main(String... args) {
Exercise226 gui = new Exercise226();
gui.setTitle("Numbers");
gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
gui.setSize(300, 200);
gui.setLocationRelativeTo(null);
gui.setVisible(true);
}
}

The JTextArea is actually where you expect it to be but has no outline border. It is usual to place the component in a JScrollPane which will give this effect:
add(new JScrollPane(jTextDisplay), BorderLayout.CENTER);
or simply
add(new JScrollPane(jTextDisplay));

To make the textArea re-size with the window, try BoxLayout. Box is "A lightweight container that uses a BoxLayout object as its layout manager."
Box p1 = new Box(BoxLayout.X_AXIS);

How could I add spacing/padding between the elements in the frame? So the text area is more visible and centered.
Borders and padding. E.G.
Compared with:
import javax.swing.*;
import java.awt.*;
import javax.swing.border.EmptyBorder;
import javax.swing.border.TitledBorder;
public class Exercise226 {
private JButton jbSort;
private JButton jbReverse;
private JButton jbAdd;
private JButton jbShuffle;
private JLabel jlAddnum;
private JTextArea jTextDisplay;
private JTextField jTextAdd;
private JPanel gui;
public Exercise226() {
gui = new JPanel(new BorderLayout(5,5));
jbSort = new JButton("Sort");
jbReverse = new JButton("Reverse");
jbShuffle = new JButton("Shuffle");
jbAdd = new JButton("Add");
jlAddnum = new JLabel("Add number here: ");
// set the size constraints using columns/rows
jTextDisplay = new JTextArea("Here I am!", 6,20);
jTextAdd = new JTextField(8);
JPanel p1 = new JPanel(new GridLayout(1,3,3,3));
p1.add(jlAddnum);
p1.add(jTextAdd);
p1.add(jbAdd);
JPanel p2 = new JPanel(new GridLayout(1,3,3,3));
p2.add(jbSort);
p2.add(jbReverse);
p2.add(jbShuffle);
JPanel textAreaContainer = new JPanel(new GridLayout());
textAreaContainer.add(new JScrollPane(jTextDisplay));
textAreaContainer.setBorder(new TitledBorder("Text Area Here"));
gui.add(p1, BorderLayout.PAGE_START);
gui.add(textAreaContainer, BorderLayout.CENTER);
gui.add(p2, BorderLayout.PAGE_END);
gui.setBorder(new EmptyBorder(4,4,4,4));
}
public Container getGui() {
return gui;
}
public static void main(String... args) {
JFrame f = new JFrame();
Exercise226 gui = new Exercise226();
f.setContentPane(gui.getGui());
f.setTitle("Numbers");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
}
}
This code:
Primarily provides 'white space' in the GUI using different constructors for the layouts that accept 2 int arguments for horizontal & vertical spacing.
Also adds 2 borders:
An empty border around the entire GUI to provide some spacing between it and the frame decorations.
A titled border around the text area, to make it very obvious.
Does implement a change for one unnecessary part of the original code. Instead of extending frame, it simply retains an instance of one.
Uses the JScrollPane container for the text area, as suggested by #Reimeus. It adds a nice beveled border of its own to an element that needs no scroll bars.
Creates a textAreaContainer specifically so that we can set a titled border to surround the scroll pane - without interfering with its existing border. It is possible to use a CompoundBorder for the scroll pane that consists of the existing border (scroll.getBorder()) & the titled border. However that gets complicated with buttons & other elements that might change borders on selection or action. So to set an 'outermost border' for a screen element (like the text area here) - I generally prefer to wrap the entire component in another container first.
Does not create and show the GUI on the EDT. Swing GUIs should be created and modified on the EDT. Left as an exercise for the user. See Concurrency in Swing for more details.
Old Code
The original code on this answer that provides the 'comparison GUI image' seen above. IT is closely based on the original code but with the text area wrapped in a scroll pane (and gaining a beveled border because of that) & given some text to display.
import javax.swing.*;
import java.awt.*;
public class Exercise226 extends JFrame {
private JButton jbSort;
private JButton jbReverse;
private JButton jbAdd;
private JButton jbShuffle;
private JLabel jlAddnum;
private JTextArea jTextDisplay;
private JTextField jTextAdd;
public Exercise226() {
jbSort = new JButton("Sort");
jbReverse = new JButton("Reverse");
jbShuffle = new JButton("Shuffle");
jbAdd = new JButton("Add");
jlAddnum = new JLabel("Add number here: ");
// set the size constraints using columns/rows
jTextDisplay = new JTextArea("Here I am!", 6,20);
jTextAdd = new JTextField(8);
setLayout(new BorderLayout());
JPanel p1 = new JPanel(new GridLayout(1,3));
p1.add(jlAddnum);
p1.add(jTextAdd);
p1.add(jbAdd);
JPanel p2 = new JPanel(new GridLayout(1,3));
p2.add(jbSort);
p2.add(jbReverse);
p2.add(jbShuffle);
add(p1, BorderLayout.NORTH);
add(new JScrollPane(jTextDisplay), BorderLayout.CENTER);
add(p2, BorderLayout.SOUTH);
}
public static void main(String... args) {
Exercise226 gui = new Exercise226();
gui.setTitle("Numbers");
gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//gui.setSize(300, 200);
gui.pack();
//gui.setLocationRelativeTo(null);
gui.setLocationByPlatform(true);
gui.setVisible(true);
}
}

Panels overlap each other when box not big enough

I have this gui; and when the height is not big enough the panes will overlap each other. I have to set it at least 200, so I can completely see the two rows; but when it is set at 200, then I have like a big empty row at the end, and I don't want that. How could I fix this? Thanks.
import java.awt.FlowLayout;
import javax.swing.*;
import java.awt.*;
public class MyFrame extends JFrame {
JButton panicButton;
JButton dontPanic;
JButton blameButton;
JButton newsButton;
JButton mediaButton;
JButton saveButton;
JButton dontSave;
public MyFrame() {
super("Crazy App");
setSize(400, 150);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel row1 = new JPanel();
panicButton = new JButton("Panic");
dontPanic = new JButton("No Panic");
blameButton = new JButton("Blame");
newsButton = new JButton("News");
//adding first row
GridLayout grid1 = new GridLayout(4, 2, 10, 10);
setLayout(grid1);
FlowLayout flow1 = new FlowLayout(FlowLayout.CENTER, 10, 10);
row1.setLayout(flow1);
row1.add(panicButton);
row1.add(dontPanic);
row1.add(blameButton);
row1.add(newsButton);
add(row1);
//adding second row
JPanel row2 = new JPanel();
mediaButton = new JButton("Blame");
saveButton = new JButton("Save");
dontSave = new JButton("No Save");
GridLayout grid2 = new GridLayout(3, 2, 10, 10);
setLayout(grid2);
FlowLayout flow2 = new FlowLayout(FlowLayout.CENTER, 10, 10);
row2.setLayout(flow2);
row2.add(mediaButton);
row2.add(saveButton);
row2.add(dontSave);
add(row2);
setVisible(true);
}
public static void main(String[] args) {
MyFrame frame = new MyFrame();
}
}

The original code set the layout for one panel on two separate occasions. For clarity, set it once in the constructor.
The 2nd layout specified 3 rows
Call pack() on the top-level container to have the GUI reduce to the minum sze needed for the components.
End result
import java.awt.FlowLayout;
import javax.swing.*;
import java.awt.*;
public class MyFrame17 extends JFrame {
JButton panicButton;
JButton dontPanic;
JButton blameButton;
JButton newsButton;
JButton mediaButton;
JButton saveButton;
JButton dontSave;
public MyFrame17() {
super("Crazy App");
setLayout(new GridLayout(2, 2, 10, 10));
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel row1 = new JPanel();
panicButton = new JButton("Panic");
dontPanic = new JButton("No Panic");
blameButton = new JButton("Blame");
newsButton = new JButton("News");
FlowLayout flow1 = new FlowLayout(FlowLayout.CENTER, 10, 10);
row1.setLayout(flow1);
row1.add(panicButton);
row1.add(dontPanic);
row1.add(blameButton);
row1.add(newsButton);
add(row1);
//adding second row
JPanel row2 = new JPanel();
mediaButton = new JButton("Blame");
saveButton = new JButton("Save");
dontSave = new JButton("No Save");
FlowLayout flow2 = new FlowLayout(FlowLayout.CENTER, 10, 10);
row2.setLayout(flow2);
row2.add(mediaButton);
row2.add(saveButton);
row2.add(dontSave);
add(row2);
pack();
setVisible(true);
}
public static void main(String[] args) {
MyFrame17 frame = new MyFrame17();
}
}
Further tips
Don't extend frame, just use an instance of one.
Build the entire GUI in a panel which can then be added to a frame, applet, dialog..
When developing test classes, give them a more sensible name than MyFrame. A good word to add is Test, then think about what is being tested. This is about the layout of buttons, so ButtonLayoutTest might be a good name.
GUIs should be started on the EDT.

Resize makes things wrong

I want to create a JInternalFrame with some components in it.
My aim is to design a bash console in Java.
My frame is made of 4 components:
JTextArea included into a JScrollPane
JLabel with the text "Cmd:"
JTextField
JButton with the text "Send"
And I have the following code:
Box box = Box.createHorizontalBox();
box.add(Box.createVerticalStrut(5));
box.add(this.cmd_label);
box.add(Box.createVerticalStrut(5));
box.add(this.cmd_input);
box.add(Box.createVerticalStrut(5));
box.add(this.submit);
box.add(Box.createVerticalStrut(5));
Box mainBox = Box.createVerticalBox();
mainBox.add(Box.createHorizontalStrut(5));
mainBox.add(this.result_scroll);
mainBox.add(Box.createHorizontalStrut(5));
mainBox.add(box);
mainBox.add(Box.createHorizontalStrut(5));
add(mainBox);
So when the frame has not been maximized, I have a correct look:
But when I maximize it, all components are incorrectly located:
So, here is my question: How can I set a weight to the components to fix their location every time, or, how can I fix it?
Thanks.

I think this would be better done with a BorderLayout. In a BorderLayout, the component specified as the center component will expand to fill as much space as possible, and the other components will remain at their preferred sizes.
int hgap = 5;
int vgap = 5;
internalFrame.getContentPane().setLayout(new BorderLayout(hgap, vgap));
internalFrame.getContentPane().add(this.result_scroll, BorderLayout.CENTER);
JPanel bottomPanel = new JPanel();
bottomPanel.add(this.cmd_label);
bottomPanel.add(this.cmd_input);
bottomPanel.add(this.submit);
internalFrame.getContentPane().add(bottomPanel, BorderLayout.SOUTH);

Here try this code, is this behaviour exceptable :
import java.awt.*;
import javax.swing.*;
public class LayoutExample
{
private void createAndDisplayGUI()
{
JFrame frame = new JFrame("LAYOUT EXAMPLE");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel centerPanel = new JPanel();
centerPanel.setLayout(new BorderLayout(5, 5));
centerPanel.setBorder(
BorderFactory.createEmptyBorder(2, 2, 2, 2));
JTextArea tarea = new JTextArea(10, 10);
tarea.setBackground(Color.DARK_GRAY.darker());
tarea.setForeground(Color.WHITE);
tarea.setCaretColor(Color.WHITE);
tarea.setLineWrap(true);
JScrollPane scrollPane = new JScrollPane(tarea);
centerPanel.add(scrollPane, BorderLayout.CENTER);
JPanel footerPanel = new JPanel();
footerPanel.setLayout(new BorderLayout(5, 5));
footerPanel.setBorder(
BorderFactory.createEmptyBorder(2, 2, 2, 2));
JLabel cmdLabel = new JLabel("Cmd : ");
JTextField tfield = new JTextField(10);
JPanel buttonPanel = new JPanel();
buttonPanel.setBorder(
BorderFactory.createEmptyBorder(2, 2, 2, 2));
JButton sendButton = new JButton("SEND");
footerPanel.add(cmdLabel, BorderLayout.LINE_START);
footerPanel.add(tfield, BorderLayout.CENTER);
buttonPanel.add(sendButton);
footerPanel.add(buttonPanel, BorderLayout.LINE_END);
frame.getContentPane().add(centerPanel, BorderLayout.CENTER);
frame.getContentPane().add(footerPanel, BorderLayout.PAGE_END);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new LayoutExample().createAndDisplayGUI();
}
});
}
}
OUTPUT :

Base problem here is what I consider a bug in JTextField's max layout hint: it's unbounded in both horizontal and vertical dimension. The latter is pure nonsense for a component designed for showing a single line of text. To fix, subclass and let it return its pref for the height, like:
JTextField cmdInput = new JTextField() {
#Override
public Dimension getMaximumSize() {
Dimension max = super.getMaximumSize();
max.height = getPreferredSize().height;
return max;
}
};
As BoxLayout respects maxSize, the excess height now will be given to the top box only.
On the long run, consider switching to a third party manager which allows fine-tuning in a all-in-one-panel approach. Yeah, here comes my current favourite: MigLayout. Compare the following lines to all the nesting and border tricks above and have fun :-)
MigLayout layout = new MigLayout("wrap 3, debug",
"[][grow, fill][]", // 3 columns, middle column filled and allows growing
"[grow, fill][]"); // two rows, first filled and allows growing
JComponent content = new JPanel(layout);
// the scrollPane in the first row spanning all columns
// and growing in both directions
content.add(new JScrollPane(new JTextArea(20, 20)), "span, grow");
// auto-wrapped to first column in second row
content.add(new JLabel("Cmd:"));
content.add(new JTextField());
content.add(new JButton("Submit"));