I am adding panels to a frame with a button click, each panel goes under the last added panel, I achieve that with setBounds, each time incrementing y position. There is a second button, that is supposed to remove the latest panel that I added. It should keep removing panels after every click. I have tried a few solutions but they all failed.
My code:
public class lab3 {
static int y = 50;
static JButton addThread;
static JPanel results;
public static void main(String[] args) {
JFrame jFrame = new JFrame();
jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jFrame.setSize(550, 650);
jFrame.setTitle("Lab3");
jFrame.setVisible(true);
JPanel panelAddThread = new JPanel();
panelAddThread.setLayout(null);
panelAddThread.setBounds(0, 0, 550, 50);
panelAddThread.setBackground(Color.red);
JLabel threadLabel = new JLabel();
threadLabel.setText("Thread count: ");
addThread = new JButton();
addThread.setBounds(300, 0, 25, 25);
addThread.setText("+");
addThread.setBorder(null);
addThread.addActionListener(e -> {
results = new JPanel();
results.setBounds(0, y, 550, 150);
results.setBackground(Color.blue);
results.setLayout(null);
jFrame.add(results);
jFrame.repaint();
y = y+ 150;
});
// Remove
JButton removeThread = new JButton();
removeThread.setBorder(null);
removeThread.setBounds(340, 0, 25, 25);
removeThread.setText("-");
removeThread.addActionListener(e -> {
});
panelAddThread.add(threadLabel);
panelAddThread.add(removeThread);
panelAddThread.add(addThread);
jFrame.add(panelAddThread); }
}
I understand that you are asking for the code for the ActionListener for removeThread (JButton).
results is actually the last JPanel that you added, so that is the JPanel that you need to remove. However, once you remove it, you need to assign it to the new, last JPanel, i.e. the second last JPanel that was added.
Method getComponents returns all the components that were added, in the order that they were added. When you remove a component from a Container and subsequently call method getComponents, the array returned will not contain the component that you just removed. Hence the new, last JPanel is the last element in the array returned by method getComponents.
All that remains is to handle the "edge" cases.
Here is the code for the actionPerformed method:
removeThread.addActionListener(e -> {
if (results != null) {
jFrame.remove(results);
jFrame.repaint();
y -= 150;
Container contentPane = jFrame.getContentPane();
Component[] cmpts = contentPane.getComponents();
int count = cmpts.length;
if (count > 1) {
results = (JPanel) cmpts[count - 1];
}
else {
results = null;
}
}
});
If the user clicks removeThread before clicking addThread then results will be null.
If there is only one, added JPanel and we remove it, then we need to set results to null.
For completeness, here is the entire program, including the above changes.
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class lab3 {
static int y = 50;
static JButton addThread;
static JPanel results;
public static void main(String[] args) {
JFrame jFrame = new JFrame();
jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jFrame.setSize(550, 650);
jFrame.setTitle("Lab3");
jFrame.setVisible(true);
JPanel panelAddThread = new JPanel();
panelAddThread.setLayout(null);
panelAddThread.setBounds(0, 0, 550, 50);
panelAddThread.setBackground(Color.red);
JLabel threadLabel = new JLabel();
threadLabel.setText("Thread count: ");
addThread = new JButton();
addThread.setBounds(300, 0, 25, 25);
addThread.setText("+");
addThread.setBorder(null);
addThread.addActionListener(e -> {
results = new JPanel();
results.setBounds(0, y, 550, 150);
results.setBackground(Color.blue);
results.setLayout(null);
jFrame.add(results);
jFrame.repaint();
y = y + 150;
});
// Remove
JButton removeThread = new JButton();
removeThread.setBorder(null);
removeThread.setBounds(340, 0, 25, 25);
removeThread.setText("-");
removeThread.addActionListener(e -> {
if (results != null) {
jFrame.remove(results);
jFrame.repaint();
y -= 150;
Container contentPane = jFrame.getContentPane();
Component[] cmpts = contentPane.getComponents();
int count = cmpts.length;
if (count > 1) {
results = (JPanel) cmpts[count - 1];
}
else {
results = null;
}
}
});
panelAddThread.add(threadLabel);
panelAddThread.add(removeThread);
panelAddThread.add(addThread);
jFrame.add(panelAddThread);
}
}
However, I would write your program differently such that it uses Swing's layout managers. Consider the following:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
public class LabThree implements Runnable {
private JFrame frame;
private JPanel container;
private JPanel results;
public void run() {
buildAndDisplayGui();
}
private void buildAndDisplayGui() {
frame = new JFrame("Lab 3");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createButtonsPanel(), BorderLayout.PAGE_START);
frame.add(createMainPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createButtonsPanel() {
JPanel buttonsPanel = new JPanel(new FlowLayout(FlowLayout.TRAILING));
buttonsPanel.setBackground(Color.red);
JButton addThreadButton = new JButton("\u2795");
addThreadButton.addActionListener(this::addThread);
buttonsPanel.add(addThreadButton);
JButton removeThreadButton = new JButton("\u2796");
removeThreadButton.addActionListener(this::removeThread);
buttonsPanel.add(removeThreadButton);
return buttonsPanel;
}
private JScrollPane createMainPanel() {
container = new JPanel();
container.setLayout(new BoxLayout(container, BoxLayout.PAGE_AXIS));
JScrollPane scrollPane = new JScrollPane(container);
scrollPane.setPreferredSize(new Dimension(570, 620));
return scrollPane;
}
private void addThread(ActionEvent event) {
results = new JPanel();
results.setBackground(Color.blue);
Dimension dim = new Dimension(550, 150);
results.setMaximumSize(dim);
results.setMinimumSize(dim);
results.setPreferredSize(dim);
container.add(results);
container.revalidate();
}
private void removeThread(ActionEvent event) {
if (results != null) {
container.remove(results);
Component[] cmpts = container.getComponents();
int count = cmpts.length;
if (count > 0) {
results = (JPanel) cmpts[count - 1];
}
else {
results = null;
}
container.revalidate();
container.repaint();
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new LabThree());
}
}
All components added to a JFrame are actually added to its content pane which, by default, is a JPanel whose [default] layout manager is BorderLayout.
Usually you should call method setVisible (of class JFrame) only after you have added all the components.
After the GUI is displayed and you add or remove components from a container (such as JPanel), you need to call method revalidate. Sometimes you also need to call method repaint after you have called method revalidate.
If you click addThreadButton many times, not all the added JPanels will be visible, hence I use JScrollPane.
The text for addThreadButton is the Unicode heavy plus symbol and the text for removeThreadButton is the heavy minus symbol.
The ActionListeners are implemented using method references.
Although not required, it is recommended to explicitly launch the event dispatch thread (EDT), which is done in method main in the above code.
How I can create a JPanel with a lot of buttons aligned float left and with vertical scrollbars only?
The buttons should be sorted like below.
1 2 3 4
5 6 7 8
9 10 11 12
If you use GridLayout, then you will not be able to add a scrollpane since it will resize automatically to fit all the components inside of it. An easier approach is to use a FlowLayout and setPreferredSize(...) to set the size of your panel. Though it is not advised to set the size of panels, you still need to have the scrollbar put into use somehow. Here is a MCVE:
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
public class Example extends JFrame {
private final int BUTTON_WIDTH = 100;
private final int BUTTON_HEIGHT = 50;
private final int BUTTON_ROWS = 3;
private final int BUTTON_COLUMNS = 4;
private final int OFFSET = 20;// the width of the actual scroll bar in pixels (approximately).
private final int PANEL_WIDTH = BUTTON_WIDTH * BUTTON_COLUMNS + OFFSET;
private final int PANEL_HEIGHT = BUTTON_HEIGHT * BUTTON_ROWS + OFFSET;
private final int SCROLL_HEIGHT = 100;//or whatever you would like...
private final JButton[] buttons = new JButton[BUTTON_ROWS * BUTTON_COLUMNS];
public Example() {
JPanel panel = new JPanel(new FlowLayout());
JScrollPane scroll = new JScrollPane(panel, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
panel.setPreferredSize(new Dimension(PANEL_WIDTH, PANEL_HEIGHT));
scroll.setPreferredSize(new Dimension(PANEL_WIDTH + OFFSET, SCROLL_HEIGHT));
for (int i = 0; i < buttons.length; i++) {
JButton button = new JButton((i + 1) + "");
buttons[i] = button;
button.setPreferredSize(new Dimension(BUTTON_WIDTH, BUTTON_HEIGHT));
panel.add(button);
}
//if you want the panel to resize when window is stretched.
//setLayout(new FlowLayout(FlowLayout.CENTER));
add(scroll);
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setVisible(true);
}
public static void main(String[] args) {
new Example();
}
}
Add the buttons to a (panel with a) grid layout to arrange them in rows and columns. Add that panel to a scroll pane, then add the scroll pane to the line start constraint of a border layout, and they will appear on the left.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class LeftAlignedButtonGrid {
private JComponent ui = null;
LeftAlignedButtonGrid() {
initUI();
}
public void initUI() {
if (ui!=null) return;
/* BorderLayout offers a LINE_START constraint that will put a
single child component on the left hand side of the GUI (in any
locale that uses left-to-right text orientation) */
ui = new JPanel(new BorderLayout(4,4));
JPanel buttonPanel = new JPanel(new GridLayout(0,4,2,2));
for (int ii=1; ii<13; ii++) {
buttonPanel.add(new JButton("" + ii));
}
ui.add(new JScrollPane(buttonPanel,
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER),
BorderLayout.LINE_START);
ui.setBorder(new EmptyBorder(4,4,4,4));
}
public JComponent getUI() {
return ui;
}
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception useDefault) {
}
LeftAlignedButtonGrid o = new LeftAlignedButtonGrid();
JFrame f = new JFrame(o.getClass().getSimpleName());
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
f.setContentPane(o.getUI());
f.pack();
// comment this out to allow the height of the GUI to be reduced,
// thus making the vertical scroll bar to have a purpose!
//f.setMinimumSize(f.getSize());
f.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
}
The above frame contains gridlayout with two rows. First row is text area,second is a panel with two checkboxes. I want to increase height of first row so that first row should be 75% of Total height and second row should be 25%. How can I do that? Here is my code snippet:
setLayout(new GridLayout(2, 0, 0, 0));
Panel text_panel = new Panel();
add(text_panel);
text_panel.setLayout(new GridLayout(1, 0, 0, 0));
JTextArea textArea = new JTextArea();
textArea.setText("text to be displayed");
JScrollPane scroll = new JScrollPane (textArea);
text_panel.add(scroll);
textArea.setLineWrap(true);
textArea.setWrapStyleWord(true);
textArea.setEditable(false);
Border border = BorderFactory.createLineBorder(Color.GRAY);
textArea.setBorder(border);
textArea.setFont(new Font("Arial",Font.PLAIN,12));
textArea.setCaretPosition(0);
textArea.requestFocus();
Panel checebox_panel = new Panel();
checebox_panel.setBackground(Color.WHITE);
add(checebox_panel);
checebox_panel.setLayout(new GridLayout(1, 0, 0, 0));
androidCheckBox = new JCheckBox("Open start page");
androidCheckBox.setBackground(Color.WHITE);
androidCheckBox.addItemListener(itemListener);
androidCheckBox.setSelected(true);
checebox_panel.add(androidCheckBox);
eclipseCheckBox = new JCheckBox("register for updates");
eclipseCheckBox.setBackground(Color.WHITE);
eclipseCheckBox.addItemListener(itemListener);
eclipseCheckBox.setSelected(true);
checebox_panel.add(eclipseCheckBox);
This is not possible with GridLayout. GridLayout will always use even spacing. Look into another layout manager.
Here is a good reference:
https://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html
With GridLayout you can't have two rows that are different sizes. Look into BoxLayout. Something like this:
JPanel content = new JPanel();
frame.getContentPane().add(content);
LayoutManager layout = new BoxLayout(content, BoxLayout.Y_AXIS);
Box boxes[] = new Box[2];
boxes[0] = Box.createHorizontalBox();
boxes[1] = Box.createHorizontalBox();
boxes[0].createGlue();
boxes[1].createGlue();
content.add(boxes[0]);
content.add(boxes[1]);
JPanel panel = new JPanel();
JPanel panel2 = new JPanel();
panel.setPreferredSize(new Dimension(500,300));
panel2.setPreferredSize(new Dimension(500,200));
boxes[0].add(panel);
boxes[1].add(panel2);
Using setPreferredSize is never optimal, but it works. This is just an example of how you could do it, I'm sure there is better ways though! ;)
"Increase a row size in Gridlayout" I came across this requirement and by trying to device a solution I got one, tried border instead grid layout. it might be helpful :)
here is the code:
import ComponentMeta.RequiredComp;
import javax.swing.*;
import java.awt.*;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class PromptPopup extends JDialog {
private final JScrollPane scrollPane = new JScrollPane();
private int rows;
private int cols;
private int vGap;
private int hGap;
private Map<String, Component> componentRepo;
public PromptPopup(JFrame parent) {
super(parent);
componentRepo = new HashMap<>();
this.setModalityType(ModalityType.APPLICATION_MODAL);
}
public void setComponentsDisplayStyle(int rows, int cols, int vGap, int hGap) {
this.rows = rows;
this.cols = cols;
this.vGap = vGap;
this.hGap = hGap;
}
public void setComponentReop() {
JTextField dynamicParamTextField = new JTextField();
this.componentRepo.put("COMPANY_CODE", dynamicParamTextField);
JTextField dynamicParamTextField2 = new JTextField();
this.componentRepo.put("DIST_CODE", dynamicParamTextField2);
JTextField dynamicParamTextField3 = new JTextField();
this.componentRepo.put("LOCA_CODE", dynamicParamTextField3);
JTextField dynamicParamTextField4 = new JTextField();
this.componentRepo.put("TOKEN_EXEC", dynamicParamTextField4);
}
public void initPopupUI() {
//Setting content panes layout
getContentPane().setLayout(new BorderLayout(0, 0));
//Creating a root panel(root container) to hold the child components
JPanel rootContainer = new JPanel();
rootContainer.setLayout(new BorderLayout());
//Creating header panel(header container) to hold the header components
JPanel header = new JPanel();
header.setLayout(new FlowLayout());
JLabel headerText = new JLabel("Source query parameters required ");
headerText.setForeground(Color.WHITE);
header.add(headerText);
header.setBackground(Color.BLUE);
//Creating footer panel(footer container ) to hold the footer components
JPanel footer = new JPanel();
footer.setLayout(new FlowLayout());
JButton executeWithParamsButton = new JButton("Execute with params");
executeWithParamsButton.setBackground(Color.BLACK);
executeWithParamsButton.setForeground(Color.WHITE);
JButton cancelButton = new JButton("Cancel");
cancelButton.setBackground(Color.RED);
cancelButton.setForeground(Color.WHITE);
footer.add(executeWithParamsButton);
footer.add(cancelButton);
footer.setBackground(Color.BLUE);
//Creating content panel(content container) to hold the all dynamically generated components
JPanel contentContainer = new JPanel();
GridLayout gridLayout = new GridLayout(this.rows, this.cols, this.hGap, this.vGap);
contentContainer.setLayout(gridLayout);
for (Map.Entry entry : componentRepo.entrySet()) {
JLabel dynamicParamLabel = new JLabel(entry.getKey().toString());
contentContainer.add(dynamicParamLabel);
contentContainer.add((Component) entry.getValue());
}
// Adding all the created containers to the root container one by one
rootContainer.add(header, BorderLayout.NORTH);
rootContainer.add(contentContainer, BorderLayout.CENTER);
rootContainer.add(footer, BorderLayout.SOUTH);
//Adding the root container to the scroll pane in order the view to be scrollable nno matter how many components are there.
scrollPane.setViewportView(rootContainer);
getContentPane().add(scrollPane);
}
}
And Here is output I wanted i.e The Header to be on top consuming space only based on it's components and same for the Center panel and The footer containing button controls.
output
Here is my simple example:
import java.awt.BorderLayout;
import java.awt.Dialog;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.util.ArrayList;
import java.util.Enumeration;
import javax.swing.AbstractButton;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JScrollPane;
import javax.swing.JRadioButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class SelectItem extends JDialog {
private static final long serialVersionUID = 1L;
private final JPanel contentPanel = new JPanel();
private String item;
private ButtonGroup group;
/**
* Launch the application.
*/
public static void main(String[] args) {
final JFrame frame = new JFrame();
frame.setBounds(100, 100, 133, 102);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(new BorderLayout(0, 0));
JButton btnSelectItem = new JButton("select item");
btnSelectItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
ArrayList<String> items = new ArrayList<String>();
for (char c = 'A'; c <= 'Z'; c++)
items.add(String.valueOf(c));
SelectItem dialog = new SelectItem(frame, items, items.get(20));
System.out.println("Item = " + dialog.showChooseDialog());
}
});
frame.getContentPane().add(btnSelectItem);
frame.setVisible(true);
}
public String showChooseDialog(){
setVisible(true);
return item;
}
/**
* Create the dialog.
*/
public SelectItem(JFrame parent, ArrayList<String> items, String selectedItem) {
super(parent, null, Dialog.ModalityType.DOCUMENT_MODAL);
setTitle("Select Item");
setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
setBounds(100, 100, 450, 300);
getContentPane().setLayout(new BorderLayout());
contentPanel.setBorder(new EmptyBorder(5, 5, 5, 5));
getContentPane().add(contentPanel, BorderLayout.CENTER);
contentPanel.setLayout(null);
JScrollPane scrollPane = new JScrollPane();
scrollPane.setBounds(0, 0, 434, 228);
contentPanel.add(scrollPane);
JPanel panel = new JPanel();
scrollPane.setViewportView(panel);
panel.setLayout(null);
int marginX = 6;
int currentY = 7;
int width = 420;
int height = 23;
int paddingY = 26;
int scrollY = 0;
group = new ButtonGroup();
for (String str: items){
JRadioButton rd = new JRadioButton(str);
rd.setBounds(marginX, currentY, width, height);
currentY = currentY + paddingY;
panel.add(rd);
group.add(rd);
if (str == selectedItem){ //or str.equals()...
group.setSelected(rd.getModel(), true);
//scrollY = rd.getY() - height/2 - scrollPane.getHeight()/2;
scrollY = rd.getY() + height/2 - scrollPane.getHeight()/2;
}
}
System.out.println("ScrollY: " + scrollY);
Dimension size = panel.getPreferredSize();
size.setSize(size.getWidth(), currentY);
panel.setPreferredSize(size);
//this.setVisible(true);
scrollPane.getVerticalScrollBar().setValue(scrollY);
panel.repaint();
panel.revalidate();
scrollPane.getVerticalScrollBar().repaint();
scrollPane.getVerticalScrollBar().revalidate();
scrollPane.repaint();
scrollPane.revalidate();
this.repaint();
this.revalidate();
{
JPanel buttonPane = new JPanel();
buttonPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
getContentPane().add(buttonPane, BorderLayout.SOUTH);
{
JButton okButton = new JButton("OK");
okButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
Enumeration<AbstractButton> iter = group.getElements();
while (iter.hasMoreElements()){
AbstractButton rd = iter.nextElement();
if (group.isSelected(rd.getModel())){
item = rd.getActionCommand();
break;
}
}
//System.out.println(group.getSelection().getActionCommand());
setVisible(false);
dispose();
}
});
okButton.setActionCommand("OK");
buttonPane.add(okButton);
getRootPane().setDefaultButton(okButton);
}
{
JButton cancelButton = new JButton("Cancel");
cancelButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
item = null;
setVisible(false);
dispose();
}
});
cancelButton.setActionCommand("Cancel");
buttonPane.add(cancelButton);
}
}
}
}
I create a list of String and then pass it to a JDialog constructor with a default string value, or selectedItem as in my code.
This dialog will display all item of the list and let the user choose one.
This is done by using JRadioButton, and the JRadioButton object with it value equals to default value will be selected by default.
Everything work fine. But I want to scroll the panel to that radio-button automatically when a dialog is open, that radio-button will be in middle of vertical alignment
Like this:
.
if (str == selectedItem){ //or str.equals()...
group.setSelected(rd.getModel(), true);
scrollY = rd.getY() + height/2 - scrollPane.getHeight()/2;
}
...
scrollPane.getVerticalScrollBar().setValue(scrollY);
But when the dialog isopened, it doesn't scroll to that position.
I know that something hasn't been updated because a dialog are not visible.
Try adding
this.setVisible(true);
before update the scrollbar, the dialog will be open twice, and in the second time, it display correctly as I want.
But i still don't know how to solve this problem.
Anyone can help me. Thanks.
(sorry for my bad grammar)
First of all:
Get rid of all the repaint() and revalidate() methods. The only time you need to use those methods is when you add/remove components from a visible GUI. In that case the order is revalidate() (to invoke the layout manager) and then repaint() (to paint the components at there new size/location).
Get rid of null layouts. Scrolling works better when you use layout managers and each component determines it own size.
Regarding your problem the maximum value of the scrollbar is only 100 at the time you execute your code, so you can't set the value to 240. I would guess this is because you have not used the pack() method on the dialog before you make it visible. You should be able to set the value of the scrollbar after the pack().
Or, maybe a better approach is the use panel.scrollRectToVisible(....). This seems to work even if you don't pack() the dialog.
A GUI with no white space appears 'crowded'. How can I provide white space without resorting to explicitly setting the position or size of components?
Using various LayoutManagers one can provide spacing between various components.
1.) BorderLayout :
Overloaded Constructor : BorderLayout(int horizontalGap, int verticalGap)
Getter and setter methods
For Horizontal Spacing : BorderLayout.getHgap() and BorderLayout.setHgap(int hgap)
For Vertical Spacing : BorderLayout.getVgap() and BorderLayout.setVgap()
2.) FlowLayout :
Overloaded Constructor : FlowLayout(int align, int hgap, int vgap)
Getter and setter methods
For Horizontal Spacing : FlowLayout.getHgap() and FlowLayout.setHgap(int hgap)
For Vertical Spacing : FlowLayout.getVgap() and FlowLayout.setVgap()
3.) GridLayout :
Overloaded Constructor : GridLayout(int rows, int columns, int hgap, int vgap)
Getter and setter methods
For Horizontal Spacing : GridLayout.getHgap() and GridLayout.setHgap(int hgap)
For Vertical Spacing : GridLayout.getVgap() and GridLayout.setVgap()
4.) GridBagLayout :
GridBagConstraints.insets
5.) CardLayout (example) :
CardLayout(int hGap, int vGap)
Example to display all constructors in action :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class LayoutExample {
private final int hGap = 5;
private final int vGap = 5;
private String[] borderConstraints = {
BorderLayout.PAGE_START,
BorderLayout.LINE_START,
BorderLayout.CENTER,
BorderLayout.LINE_END,
BorderLayout.PAGE_END
};
private JButton[] buttons;
private GridBagConstraints gbc;
private JPanel borderPanel;
private JPanel flowPanel;
private JPanel gridPanel;
private JPanel gridBagPanel;
private JPanel cardPanel;
public LayoutExample() {
buttons = new JButton[16];
gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.FIRST_LINE_START;
gbc.insets = new Insets(hGap, vGap, hGap, vGap);
}
private void displayGUI() {
JFrame frame = new JFrame("Layout Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel contentPane = new JPanel(
new GridLayout(0, 1, hGap, vGap));
contentPane.setBorder(
BorderFactory.createEmptyBorder(hGap, vGap, hGap, vGap));
borderPanel = new JPanel(new BorderLayout(hGap, vGap));
borderPanel.setBorder(
BorderFactory.createTitledBorder("BorderLayout"));
borderPanel.setOpaque(true);
borderPanel.setBackground(Color.WHITE);
for (int i = 0; i < 5; i++) {
buttons[i] = new JButton(borderConstraints[i]);
borderPanel.add(buttons[i], borderConstraints[i]);
}
contentPane.add(borderPanel);
flowPanel = new JPanel(new FlowLayout(
FlowLayout.CENTER, hGap, vGap));
flowPanel.setBorder(
BorderFactory.createTitledBorder("FlowLayout"));
flowPanel.setOpaque(true);
flowPanel.setBackground(Color.WHITE);
for (int i = 5; i < 8; i++) {
buttons[i] = new JButton(Integer.toString(i));
flowPanel.add(buttons[i]);
}
contentPane.add(flowPanel);
gridPanel = new JPanel(new GridLayout(2, 2, hGap, vGap));
gridPanel.setBorder(
BorderFactory.createTitledBorder("GridLayout"));
gridPanel.setOpaque(true);
gridPanel.setBackground(Color.WHITE);
for (int i = 8; i < 12; i++) {
buttons[i] = new JButton(Integer.toString(i));
gridPanel.add(buttons[i]);
}
contentPane.add(gridPanel);
gridBagPanel = new JPanel(new GridBagLayout());
gridBagPanel.setBorder(
BorderFactory.createTitledBorder("GridBagLayout"));
gridBagPanel.setOpaque(true);
gridBagPanel.setBackground(Color.WHITE);
buttons[12] = new JButton(Integer.toString(12));
addComp(gridBagPanel, buttons[12], 0, 0, 1, 1
, GridBagConstraints.BOTH, 0.33, 0.5);
buttons[13] = new JButton(Integer.toString(13));
addComp(gridBagPanel, buttons[13], 1, 0, 1, 1
, GridBagConstraints.BOTH, 0.33, 0.5);
buttons[14] = new JButton(Integer.toString(14));
addComp(gridBagPanel, buttons[14], 0, 1, 2, 1
, GridBagConstraints.BOTH, 0.66, 0.5);
buttons[15] = new JButton(Integer.toString(15));
addComp(gridBagPanel, buttons[15], 2, 0, 1, 2
, GridBagConstraints.BOTH, 0.33, 1.0);
contentPane.add(gridBagPanel);
cardPanel = new JPanel(new CardLayout(hGap, vGap));
cardPanel.setBorder(
BorderFactory.createTitledBorder("CardLayout"));
cardPanel.setOpaque(true);
cardPanel.setBackground(Color.WHITE);
cardPanel.add(getPanel(Color.BLUE));
cardPanel.add(getPanel(Color.GREEN));
contentPane.add(cardPanel);
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel getPanel(Color bColor) {
JPanel panel = new JPanel(new FlowLayout(
FlowLayout.CENTER, hGap, vGap));
panel.setOpaque(true);
panel.setBackground(bColor.darker().darker());
JButton swapperButton = new JButton("Next");
swapperButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
CardLayout cardLayout = (CardLayout) cardPanel.getLayout();
cardLayout.next(cardPanel);
}
});
panel.add(swapperButton);
return panel;
}
private void addComp(JPanel panel, JComponent comp
, int x, int y, int gWidth
, int gHeight, int fill
, double weightx, double weighty) {
gbc.gridx = x;
gbc.gridy = y;
gbc.gridwidth = gWidth;
gbc.gridheight = gHeight;
gbc.fill = fill;
gbc.weightx = weightx;
gbc.weighty = weighty;
panel.add(comp, gbc);
}
public static void main(String[] args) {
Runnable runnable = new Runnable(){
#Override
public void run() {
new LayoutExample().displayGUI();
}
};
EventQueue.invokeLater(runnable);
}
}
OUTPUT :
There are a number of ways in a Swing GUI to provide a separation between components, and white space around components:
JToolBar has the methods addSeparator() & addSeparator(Dimension).
JMenu uses a spacing component better suited to menus, available through addSeparator().
But more generally, look to:
The spacing as can be defined in the layout constructors.
Borders.
Here is an example of using the layout separator hGap & vGap values & borders (specifically an EmptyBorder) to provide 'white' (actually shown as red to make it very obvious) space. Adjust the spinners to see the result.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.event.*;
public class WhiteSpace {
private JPanel gui = null;
private BorderLayout mainLayout =
new BorderLayout(0, 0);
private final FlowLayout buttonLayout =
new FlowLayout(FlowLayout.CENTER, 0, 0);
private final JPanel buttonPanel = new JPanel(buttonLayout);
private final SpinnerNumberModel hModel =
new SpinnerNumberModel(0, 0, 15, 1);
private final SpinnerNumberModel vModel =
new SpinnerNumberModel(0, 0, 15, 1);
private final SpinnerNumberModel hBorderModel =
new SpinnerNumberModel(0, 0, 15, 1);
private final SpinnerNumberModel vBorderModel =
new SpinnerNumberModel(0, 0, 15, 1);
private ChangeListener changeListener;
public Container getGui() {
if (gui == null) {
gui = new JPanel(mainLayout);
gui.setBackground(Color.RED);
JTree tree = new JTree();
tree.setVisibleRowCount(10);
for (int ii = tree.getRowCount(); ii > -1; ii--) {
tree.expandRow(ii);
}
gui.add(new JScrollPane(
tree,
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER),
BorderLayout.LINE_START);
gui.add(new JScrollPane(new JTextArea(10, 30)));
gui.add(buttonPanel, BorderLayout.PAGE_START);
changeListener = (ChangeEvent e) -> {
int hGap = hModel.getNumber().intValue();
int vGap = vModel.getNumber().intValue();
int hBorder = hBorderModel.getNumber().intValue();
int vBorder = vBorderModel.getNumber().intValue();
adjustWhiteSpace(hGap, vGap, hBorder, vBorder);
};
addModel("H Gap", hModel);
addModel("V Gap", vModel);
addModel("H Border", hBorderModel);
addModel("V Border", vBorderModel);
}
return gui;
}
private void addModel(String label, SpinnerNumberModel model) {
buttonPanel.add(new JLabel(label));
final JSpinner spinner = new JSpinner(model);
spinner.addChangeListener(changeListener);
buttonPanel.add(spinner);
}
private void adjustWhiteSpace(
int hGap, int vGap, int hBorder, int vBorder) {
mainLayout.setHgap(hGap);
mainLayout.setVgap(vGap);
buttonLayout.setHgap(hGap);
gui.setBorder(new EmptyBorder
(vBorder, hBorder, vBorder, hBorder));
Container c = gui.getTopLevelAncestor();
if (c instanceof Window) {
Window w = (Window) c;
w.pack();
}
}
public static void main(String[] args) {
Runnable r = () -> {
WhiteSpace ws = new WhiteSpace();
Container gui1 = ws.getGui();
JFrame f = new JFrame("White (OK Red) Space");
f.add(gui1);
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
f.setResizable(false);
f.pack();
f.setVisible(true);
};
SwingUtilities.invokeLater(r);
}
}
When you use BoxLayout, Box.createVerticalGlue() method can help you to make some white space.
Another method is BorderFactory.createEmptyBorder(int top, int left, int bottom, int right). It can help you to make some white space around component.
Thanks for Andrew Thompson's remind.I've revised BoxLayout in recent days and I find that Box.createVerticalGlue() can add some white space depend on the panel's size and you can not set the explicit pixel value of the length of white space.But Box.createVerticalStrut() can do that. Here is a MCTaRE and show the effect of those two methods.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;
public class WhiteSpace extends JFrame{
static WhiteSpace whiteSpace;
DemoPanel demoPanel;
boolean withGlue;
JSpinner spinner;
public WhiteSpace(){
initialWindow();
demoPanel = new DemoPanel();
ActionPanel actionPanel = new ActionPanel();
setLayout(new BorderLayout());
getContentPane().add(actionPanel,BorderLayout.NORTH);
getContentPane().add(demoPanel,BorderLayout.CENTER);
setVisible(true);
}
public void initialWindow(){
setSize(220, 300);
setTitle("White Space");
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
//Show the window in the middle of the screen
}
/**
* #param args
*/
public static void main(String[] args) {
Runnable runnable = new Runnable() {
#Override
public void run() {
whiteSpace = new WhiteSpace();
}
};
SwingUtilities.invokeLater(runnable);
}
class DemoPanel extends JPanel{
//Show the vertical white space between label1 and label2
JLabel label1;
JLabel label2;
public void initialDemoPanel(){
setBorder(BorderFactory.createTitledBorder(getBorder(), "DemoPanel", TitledBorder.LEADING, TitledBorder.TOP, new Font("Default",Font.PLAIN,10), Color.gray));
setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
label1 = new JLabel("This is first line");
label2 = new JLabel("This is second line");
}
public DemoPanel(){
initialDemoPanel();
add(label1);
if(withGlue){
add(Box.createVerticalGlue());
}
add(label2);
}
public DemoPanel(int strutValue){
initialDemoPanel();
add(label1);
add(Box.createVerticalStrut(strutValue));
add(label2);
}
}
class ActionPanel extends JPanel{
public ActionPanel(){
setBorder(BorderFactory.createTitledBorder(getBorder(), "ActionPanel", TitledBorder.LEADING, TitledBorder.TOP, new Font("Default",Font.PLAIN,10), Color.gray));
setLayout(new BoxLayout(this,BoxLayout.X_AXIS));
JRadioButton glueButton = new JRadioButton("With Glue");
glueButton.addActionListener(new glueButtonListener());
add(glueButton);
add(Box.createHorizontalStrut(10));
//To create horizontal white space
JLabel strutLabel = new JLabel("Strut Value");
add(strutLabel);
spinner = new JSpinner(new SpinnerNumberModel(0,0,50,1));
spinner.addChangeListener(new spinnerListener());
add(spinner);
//public SpinnerNumberModel(Number value,Comparable minimum,Comparable maximum,Number stepSize)
}
}
class glueButtonListener implements ActionListener{
#Override
public void actionPerformed(ActionEvent e) {
spinner.setValue(new Integer(0));
withGlue = (withGlue == true ? false:true);
whiteSpace.getContentPane().remove(demoPanel);
demoPanel = new DemoPanel();
whiteSpace.getContentPane().add(demoPanel,BorderLayout.CENTER);
whiteSpace.getContentPane().validate();
}
}
class spinnerListener implements ChangeListener{
#Override
public void stateChanged(ChangeEvent e) {
int strutValue = (Integer) spinner.getValue();
whiteSpace.getContentPane().remove(demoPanel);
demoPanel = new DemoPanel(strutValue);
whiteSpace.getContentPane().add(demoPanel,BorderLayout.CENTER);
whiteSpace.getContentPane().validate();
}
}
}
Box.createHorizontalGlue() and Box.createHorizontalStrut(int height) can be used too. Besides, Box.createRigidArea(Dimension d) has the ability too create white space too.
MigLayout has multiple ways of creating space. (A space is called a gap in this layout.)
Gaps can be created at the highest level with layout constraints, it is possible to
create gaps between rows and column and gaps can be also set between individual
components with component constraints. There are also specific gaps around the borders
of a container called insets which have their own specific keyword to be set.
The following example creates all these kinds of gaps:
package com.zetcode;
import java.awt.EventQueue;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import net.miginfocom.swing.MigLayout;
public class MigLayoutGaps2 extends JFrame {
public MigLayoutGaps2() {
initUI();
setTitle("Gaps");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
}
private void initUI() {
JPanel base = new JPanel(new MigLayout("flowy, ins 30, gap 15"));
setContentPane(base);
JPanel pnl1 = new JPanel();
pnl1.setBorder(
BorderFactory.createTitledBorder("Grid gaps")
);
pnl1.setLayout(new MigLayout("gap 5 5, ins 10, wrap 3"));
pnl1.add(new JButton("1"));
pnl1.add(new JButton("2"));
pnl1.add(new JButton("3"));
pnl1.add(new JButton("4"));
pnl1.add(new JButton("5"));
pnl1.add(new JButton("6"));
JPanel pnl2 = new JPanel();
pnl2.setBorder(
BorderFactory.createTitledBorder("Column gaps")
);
pnl2.setLayout(new MigLayout("wrap 3", "[]10[]"));
JLabel lbl1 = new JLabel();
lbl1.setBorder(
BorderFactory.createEtchedBorder()
);
JLabel lbl2 = new JLabel();
lbl2.setBorder(
BorderFactory.createEtchedBorder()
);
JLabel lbl3 = new JLabel();
lbl3.setBorder(
BorderFactory.createEtchedBorder()
);
pnl2.add(lbl1, "w 40, h 110");
pnl2.add(lbl2, "w 40, h 110");
pnl2.add(lbl3, "w 40, h 110");
JPanel pnl3 = new JPanel();
pnl3.setBorder(
BorderFactory.createTitledBorder("Row gaps")
);
pnl3.setLayout(new MigLayout("wrap", "", "[]15[]"));
JLabel lbl4 = new JLabel();
lbl4.setBorder(
BorderFactory.createEtchedBorder()
);
JLabel lbl5 = new JLabel();
lbl5.setBorder(
BorderFactory.createEtchedBorder()
);
JLabel lbl6 = new JLabel();
lbl6.setBorder(
BorderFactory.createEtchedBorder()
);
pnl3.add(lbl4, "w 150, h 20");
pnl3.add(lbl5, "w 150, h 20");
pnl3.add(lbl6, "w 150, h 20");
JPanel pnl4 = new JPanel();
pnl4.setBorder(
BorderFactory.createTitledBorder("Component gaps")
);
pnl4.setLayout(new MigLayout());
pnl4.add(new JLabel("Name:"), "gapright 5");
pnl4.add(new JTextField(10), "gapbottom 20, gaptop 20");
base.add(pnl1);
base.add(pnl2);
base.add(pnl3);
base.add(pnl4);
pack();
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
MigLayoutGaps2 ex = new MigLayoutGaps2();
ex.setVisible(true);
}
});
}
}
We have four panels in the layout. Each of this panels has a MigLayout manager.
JPanel base = new JPanel(new MigLayout("flowy, ins 30, gap 15"));
This line creates container insets and vertical gaps between panels.
pnl1.setLayout(new MigLayout("gap 5 5, ins 10, wrap 3"));
Here we apply gaps for the whole grid structure and also set container gaps.
pnl2.setLayout(new MigLayout("wrap 3", "[]10[]"));
This line creates gaps between columns.
pnl3.setLayout(new MigLayout("wrap", "", "[]15[]"));
Row gaps are defined with this code.
pnl4.add(new JLabel("Name:"), "gapright 5");
pnl4.add(new JTextField(10), "gapbottom 20, gaptop 20");
Finally, it is possible to create gaps between individual components.
JGoodies FormLayout.
Author Karsten Lentzsch has a collection of presentations on UI design. In particular this PDF speaks to the need for aesthetic whitespace. Adding meaningful space while also paying attention to clutter separates the wheat from the chaff.
Whenever I have this issue, I just use JPanels. For example in a GridLayout:
JFrame frame = new JFrame;
frame.setLayout(new GridLayout(2, 0));
//We want the bottom left to be blank
frame.add(new JLabel("Top Left"));
frame.add(new JLabel("Top Right"));
//This is the position we want empty
frame.add(new JPanel());
//Now we can continue with the rest of the script