the program below is to position a jpanel at the top left conner of jframe with gridbaglayout but instead a very small box is displayed in center of jframe. when I set the layout of jframe to null, the jpanel displays fine. can someone tell me why the jpanel is compressed to the center of frame with gridbaglayout? i really need to use gridbag. please help
import java.awt.*;
import javax.swing.*; //swing package
public class Major {
//defining the constructor
public Major() {
JFrame maFrame = new JFrame("The main screen"); //creating main Jframe
JPanel headPanel = new JPanel(); //creating the header panel
maFrame.setSize(900, 700); //setting size
maFrame.setBackground(Color.LIGHT_GRAY); //setting color of frame
Container container = maFrame.getContentPane();
container.setLayout(new GridBagLayout()); //setting layout of main frame
GridBagConstraints cns = new GridBagConstraints(); //creating constraint
cns.gridx = 0;
cns.gridy = 0;
maFrame.setLocationRelativeTo(null); //centering frame
headPanel.setBackground(Color.WHITE);
headPanel.setSize(200, 150);
container.add(headPanel, cns);
maFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //setting the default close operation of JFrame
maFrame.setVisible(true); //making the frame visible
}
//defining the main method
public static void main(String[] args) {
new Major(); //instantiating the class
}
}
Seems like you forgot to provide, weightx and weighty constraints to your GridBagConstraints, As you provide them, you will see your JPanel.
Here I had modified your code with those Constraints.
And never use this line, headPanel.setSize(200, 150);, as I had commented it out, since the constraints I had mentioned will sort this out for you.
Adding a new Code with image :
import java.awt.*;
import javax.swing.*; //swing package
public class Major
{
//defining the constructor
public Major()
{
JFrame maFrame = new JFrame("The main screen"); //creating main Jframe
JPanel headPanel = new JPanel(); //creating the header panel
maFrame.setBackground(Color.LIGHT_GRAY); //setting color of frame
Container container = maFrame.getContentPane();
container.setLayout(new GridBagLayout()); //setting layout of main frame
GridBagConstraints cns = new GridBagConstraints(); //creating constraint
cns.gridx = 0;
cns.gridy = 0;
//cns.gridwidth = 3;
//cns.gridheight = 4;
cns.weightx = 0.3;
cns.weighty = 0.7;
cns.anchor = GridBagConstraints.FIRST_LINE_START;
cns.fill = GridBagConstraints.BOTH;
maFrame.setLocationRelativeTo(null); //centering frame
headPanel.setBackground(Color.WHITE);
container.add(headPanel, cns);
JPanel panel = new JPanel();
panel.setBackground(Color.BLUE);
cns.gridx = 1;
cns.gridy = 0;
//cns.gridwidth = 7;
//cns.gridheight = 4;
cns.weightx = 0.7;
cns.weighty = 0.7;
cns.anchor = GridBagConstraints.PAGE_START;
cns.fill = GridBagConstraints.BOTH;
container.add(panel, cns);
JPanel panel1 = new JPanel();
panel1.setBackground(Color.DARK_GRAY);
cns.gridx = 0;
cns.gridy = 1;
cns.gridwidth = 2;
//cns.gridheight = 4;
cns.weightx = 1.0;
cns.weighty = 0.3;
cns.anchor = GridBagConstraints.LAST_LINE_START;
cns.fill = GridBagConstraints.BOTH;
container.add(panel1, cns);
//JButton button = new JButton("BUTTON");
//headPanel.add(button);
maFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //setting the default close operation of JFrame
maFrame.pack();
maFrame.setVisible(true); //making the frame visible
}
//defining the main method
public static void main(String[] args)
{
Runnable runnable = new Runnable()
{
public void run()
{
new Major(); //instantiating the class
}
};
SwingUtilities.invokeLater(runnable);
}
}
here is the output :
You must set the weightx and weighty of at least one GridBagConstraint to some value greater than 0.0!
The weight attributes are are used to indicate what happens with extra space if the whole layout is smaller than the available space. If all weights (for one direction) are zero, the default value, the whole layout is centered. If at least one weight is greater than zero, the extra space is distributed to the columns or rows in proportion to its weight, so the layout will occupy all available space.
Related
I have JTextFields and JLabels added to my JPanel (from left to right) every time the JButton is pressed. However, every new JTextField and JLabelthat is added becomes smaller and smaller. How do I fix this?
Also I would like to add a JScrollPane to the JPanel but having problems doing so.
public class MyExample
{
// Field members
static JPanel panel = new JPanel();
static Integer indexer = 1;
static List<JLabel> listOfLabels = new ArrayList<JLabel>();
static List<JTextField> listOfTextFields = new ArrayList<JTextField>();
static JScrollPane scrollPane = new JScrollPane( panel );
public static void main(String[] args)
{
// Construct frame
JFrame frame = new JFrame();
frame.setLayout(new GridBagLayout());
frame.setPreferredSize(new Dimension(2000, 2000));
frame.setTitle("My Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(scrollPane);
// Frame constraints
GridBagConstraints frameConstraints = new GridBagConstraints();
// Construct button
JButton addButton = new JButton("Add");
addButton.addActionListener(new ButtonListener());
// Add button to frame
frameConstraints.gridx = 0;
frameConstraints.gridy = 0;
frame.add(addButton, frameConstraints);
// Construct panel
panel.setPreferredSize(new Dimension(1000, 1000));
panel.setLayout(new GridBagLayout());
panel.setBorder(LineBorder.createBlackLineBorder());
// Add panel to frame
frameConstraints.gridx = 0;
frameConstraints.gridy = 1;
frameConstraints.weighty = 1;
frame.add(panel, frameConstraints);
// Pack frame
frame.pack();
// Make frame visible
frame.setVisible(true);
}
static class ButtonListener implements ActionListener
{
#Override
public void actionPerformed(ActionEvent arg0)
{
// Clear panel
panel.removeAll();
// Create label and text field
JTextField jTextField = new JTextField();
jTextField.setSize(100, 200);
listOfTextFields.add(jTextField);
listOfLabels.add(new JLabel("Label " + indexer));
// Create constraints
GridBagConstraints textFieldConstraints = new GridBagConstraints();
GridBagConstraints labelConstraints = new GridBagConstraints();
// Add labels and text fields
for(int i = 0; i < indexer; i++)
{
// Text field constraints
textFieldConstraints.gridx = i;
textFieldConstraints.fill = GridBagConstraints.HORIZONTAL;
textFieldConstraints.weightx = 0.5;
textFieldConstraints.insets = new Insets(10, 10, 10, 10);
textFieldConstraints.gridy = 1;
// Label constraints
labelConstraints.gridx = i;
labelConstraints.gridy = 0;
labelConstraints.insets = new Insets(10, 10, 10, 10);
// Add them to panel
panel.add(listOfLabels.get(i), labelConstraints);
panel.add(listOfTextFields.get(i), textFieldConstraints);
}
// Align components
GridBagConstraints c = new GridBagConstraints();
c.gridx = 0;
c.gridy = indexer;
c.weighty = 1;
panel.add(new JLabel(), c);
// Increment indexer
indexer++;
panel.updateUI();
}
}
}
However, every new JTextField and JLabelthat is added becomes smaller and smaller. How do I fix this?
panel.setPreferredSize(new Dimension(1000, 1000));
Don't set the preferred size. If the size is fixed then as you add more components they need to shrink to fit in the allowed space.
Don't attempt to set the size of any component. Let the layout manager do its job and determine the preferred size of the panel.
When creating a JTextField the code should be something like:
//JTextField jTextField = new JTextField();
JTextField jTextField = new JTextField(10);
This will allow the text field to determine its own preferred size to dispaly about 10 characters.
panel.updateUI();
Don't use updateUI(). That is used internally by Swing when you change the LAF. When you remove/add components you should be using:
panel.revalidate();
panel.repaint();
As for the JScrollPane with panel as a viewport, you should not be adding the panel to the frame at all - setting it as the viewport (like you're doing in the JScrollPane constructor) and adding the JScrollPane is sufficient. Adding the panel itself may be the cause of your problem.
As for the shrinking problem, I am still trying to understand your layout code - your use of GridBagLayout seems a tad overcomplicated to me. Maybe you can draw a simple sketch of how you would like the layout look?
I have splitted frames into three parts such as horizontal part in pink background and vertical part in yellow and blue background like in the image using GridBagConstraints,enter image description here
I'm using the below code to do this,
public Main()
{
JFrame maFrame = new JFrame("The main screen"); //creating main Jframe
maFrame.setSize(1000, 700);
Container container = maFrame.getContentPane();
container.setLayout(new GridBagLayout()); //setting layout of main frame
GridBagConstraints cns = new GridBagConstraints(); //creating constraint
JPanel headPanel = new JPanel(); //creating the header panel
cns.gridx = 0;
cns.gridy = 1;
cns.weightx = 0.3;
cns.weighty = 0.7;
cns.anchor = GridBagConstraints.FIRST_LINE_START;
cns.fill = GridBagConstraints.BOTH;
maFrame.setLocationRelativeTo(null); //centering frame
headPanel.setBackground(Color.YELLOW);
container.add(headPanel, cns);
JPanel panel = new JPanel();
panel.setBackground(Color.BLUE);
cns.gridx = 1;
cns.gridy = 1;
cns.weightx = 0.7;
cns.weighty = 0.7;
cns.anchor = GridBagConstraints.PAGE_START;
cns.fill = GridBagConstraints.BOTH;
container.add(panel, cns);
JPanel panel1 = new JPanel();
panel1.setBackground(Color.PINK);
cns.gridx = 0;
cns.gridy = 0;
cns.gridwidth = 2;
cns.weightx = 1.0;
cns.weighty = 0.3;
cns.anchor = GridBagConstraints.LAST_LINE_START;
cns.fill = GridBagConstraints.BOTH;
container.add(panel1, cns);
maFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //setting the default close operation of JFrame
maFrame.pack();
maFrame.setVisible(true); //making the frame visible
}
I want to split the pink background parts into 3 parts and yellow background into two parts. I have tried to do this. But its not working for me. I do not want to use splitpane to do this. Is it possible to achieve it using GridBagConstraints? Could you please suggest me an idea to do this? thanks in advance.
Simple way to do this using GridLayout and separate the contentPane into two row and then bottom row which is divided into two columns.
import javax.swing.*;
import java.awt.*;
class JpanelSplit {
JFrame frame;
JPanel contentPane;
JPanel pinkPanel;
JPanel yellowPanel;
JPanel bluePanel;
JPanel twoPanelContainer;
public JpanelSplit() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
contentPane = new JPanel(new GridLayout(2,1));
pinkPanel = new JPanel();
pinkPanel.setBackground(Color.PINK);
yellowPanel = new JPanel();
yellowPanel.setBackground(Color.YELLOW);
bluePanel = new JPanel();
bluePanel.setBackground(Color.BLUE);
twoPanelContainer = new JPanel(new GridLayout(1,2));
twoPanelContainer.add(yellowPanel);
twoPanelContainer.add(bluePanel);
contentPane.add(pinkPanel);
contentPane.add(twoPanelContainer);
frame.setContentPane(contentPane);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
new JpanelSplit();
}
}
I am trying to write a program where there are 2 panels at all times. The left panel will be a menu with buttons, while the right panel will change depending on the buttons pushed in either panel.
Right now i am stuck. when clicking the "recipeRolodexButton" nothing happends. What i want to happen is, the right panel is either removed and replaced by my panel method, or it is overwritten by another panel.
public class Window extends JFrame implements ActionListener{
private static final long serialVersionUID = 1L;
//Buttons
JButton recipeRolodexButton = new JButton("Recipe Rolodex");
JButton groceryFinanceButton = new JButton("Grocery Finance");
JButton testButton1 = new JButton("Test Button");
JPanel homeLeftPanel = new JPanel();
JPanel homeRightPanel = new JPanel();
RolodexOptionsPane rop = new RolodexOptionsPane();
public static void main(String[] args){
new Window();
}
public Window(){
//declarations
Toolkit tk = Toolkit.getDefaultToolkit();
Dimension dim = new Dimension();
dim = tk.getScreenSize();
GridBagConstraints gbcl = new GridBagConstraints();
//setting up the window
this.setVisible(true);
this.setSize(550,300);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.setTitle("Food Management");
int xPosition = ( (dim.width / 2) - this.getWidth() / 2);
int yPosition = ( (dim.height / 2) - (this.getHeight() / 2));
this.setLocation(xPosition, yPosition);
this.setLayout(new GridBagLayout());
this.setResizable(false);
//Add Action Listeners
recipeRolodexButton.addActionListener(this);;
groceryFinanceButton.addActionListener(this);
testButton1.addActionListener(this);
//Setting up Main Panels
homeLeftPanel.setBackground(Color.BLUE);
homeLeftPanel.setLayout(new GridBagLayout());
homeRightPanel.setBackground(Color.BLACK);
homeRightPanel.setLayout(new GridBagLayout());
// setting the Button constraints in the main Left Panel buttons
gbcl.anchor = GridBagConstraints.CENTER;
gbcl.fill = GridBagConstraints.HORIZONTAL;
gbcl.gridy = 0;
gbcl.gridx = 0;
gbcl.ipady = 4;
gbcl.insets = new Insets(15,0,0,0);
homeLeftPanel.add(recipeRolodexButton,gbcl);
gbcl.gridy = 1;
homeLeftPanel.add(groceryFinanceButton, gbcl);
gbcl.gridy = 2;
homeLeftPanel.add(testButton1, gbcl);
// setting up the buttons in the main right panel
// EXECUTION!!!!!!!!!!!!
PanelSet(homeLeftPanel,homeRightPanel);
}
public void PanelSet(JPanel left , JPanel right){
GridBagConstraints gbcLeft = new GridBagConstraints();
GridBagConstraints gbcRight = new GridBagConstraints();
//positioning the panels
gbcLeft.fill = GridBagConstraints.BOTH;
gbcLeft.gridx = 0;
gbcLeft.gridy = 0;
gbcLeft.weightx = .15;
gbcLeft.weighty = .5;
gbcRight.fill = GridBagConstraints.BOTH;
gbcRight.gridx = 1;
gbcRight.gridy = 0;
gbcRight.weightx = .85;
this.add(left,gbcLeft);
this.add(right,gbcRight);
}
public void actionPerformed(ActionEvent e) {
if(e.getSource() == recipeRolodexButton){
PanelSet(recipeRolladexButton,rop);
}
}
}
sorry about the spacing. When copying my code over, the indentation was lost.
while the right panel will change depending on the buttons pushed in either panel.
You should be using a Card Layout for the right panel. Then when you click a button you just specify the name of the panel to be displayed and the CardLayout will do the rest.
The tutorial has a working example that shows how to swap panels when selecting an item from a combo box.
I'm prgramming a simple input diagram in Swing. I use boxLayout to create a simple GUI of user input. Problem is that creating a horizontal strut between the JPanel of all the labels and the JPanel of the JTextFields causes the whole panel to shift downwards (weird) this is the whole panel:
private JPanel secondCard() {
//main panel. set the boxlayout
secondCard = new JPanel();
secondCard.setLayout(new BoxLayout(secondCard,BoxLayout.Y_AXIS));
// create vertical strut for looks
secondCard.add(Box.createVerticalStrut(20));
// create title. center it.
JLabel title = new JLabel("Configure main network parameters ");
title.setAlignmentX(CENTER_ALIGNMENT);
secondCard.add(title);
// create vertical strut for looks
secondCard.add(Box.createVerticalStrut(20));
// create panel for the description labels
JPanel labelPanel = new JPanel();
labelPanel.setLayout(new BoxLayout(labelPanel,BoxLayout.Y_AXIS));
labelPanel.setAlignmentX(LEFT_ALIGNMENT);
JLabel inPut =new JLabel("number of inputs");
inPut.setAlignmentX(LEFT_ALIGNMENT);
labelPanel.add(inPut);
inPut =new JLabel("number of outputs");
inPut.setAlignmentX(LEFT_ALIGNMENT);
labelPanel.add(inPut);
inPut =new JLabel("number of layers");
inPut.setAlignmentX(LEFT_ALIGNMENT);
labelPanel.add(inPut);
JPanel textFieldPanel = new JPanel();
textFieldPanel.setLayout(new BoxLayout(textFieldPanel,BoxLayout.Y_AXIS));
textFieldPanel.setAlignmentX(LEFT_ALIGNMENT);
JTextField inputTextField = new JTextField();
inputTextField.setAlignmentX(LEFT_ALIGNMENT);
textFieldPanel.add(inputTextField);
inputTextField.setMinimumSize(new Dimension(0,0));
inputTextField = new JTextField();
inputTextField.setAlignmentX(LEFT_ALIGNMENT);
textFieldPanel.add(inputTextField);
inputTextField.setMinimumSize(new Dimension(0,0));
inputTextField = new JTextField();
inputTextField.setAlignmentX(LEFT_ALIGNMENT);
textFieldPanel.add(inputTextField);
inputTextField.setMinimumSize(new Dimension(0,0));
textFieldPanel.setMaximumSize(new Dimension(50, labelPanel.getMaximumSize().height));
JPanel inputPanel = new JPanel();
inputPanel.setLayout(new BoxLayout(inputPanel,BoxLayout.X_AXIS));
inputPanel.setAlignmentX(CENTER_ALIGNMENT);
inputPanel.add(labelPanel);
//this is the problem strut!! it causes inputPanel to shift downwards
inputPanel.add(Box.createHorizontalStrut(20));
inputPanel.add(textFieldPanel);
secondCard.add(inputPanel);
return secondCard;
}
without the strut it looks like:
With strut it looks like (I know I suck at picture editing):
You are adding a Box strut to a BoxLayout.
As the javadoc states, createHorizontalStrut(int width):
Creates an invisible, fixed-width component. In a horizontal box, you
typically use this method to force a certain amount of space between
two components. In a vertical box, you might use this method to force
the box to be at least the specified width. The invisible component
has no height unless excess space is available, in which case it takes
its share of available space, just like any other component that has
no maximum height.
As such, it is filling the height between your title JLabel and the bottom of the JPanel.
You might want to consider using Box.createRigidArea(new Dimension(20, height)) instead, where height could be specified or set to the height of labelPanel.
Or, you could reconsider the layout for your JPanel - take a look at the visual guide.
For future reference, if you cannot make sense of your Swing layout, try putting adding a coloured LineBorder to the JComponents you're unsure of. In this case, the Box struts are not JComponents but Components, so you'd have to put them into a JPanel, but this would at least have shown you what space each component was taking up in your top-level JPanel.
use Cardlayout for wizard logics
put JLabel(Configure ...., JLabel.CENTER) to the BorderLayout.NORTH
put JPanel with JButtons to the BorderLayout.SOUTH
put JPanel with SpringLayout, GridLayout, or GridBagLayout to the BorderLayout.CENTER
Top-Level Container have got implemened BorderLayout by default, then there no reason to re_define BorderLayout
above mentioned steps are called NestedLayout
alternative are put all JComponents by using GridBagLayout, SpringLayout or todays MigLayout to the one JPanel, but why bothering
Example of a nested layout, one using BorderLayout, FlowLayout (JPanel's default), and GridBagLayout:
import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.util.HashMap;
import java.util.Map;
import javax.swing.*;
public class LayoutFoo {
private static final String TITLE = "Configure Main Foobar Parameters";
private static final String[] LABEL_TEXTS = {
"Number of Spams", "Number of Frapzats", "Number of Zignuts"
};
private static final int TEXTFIELD_SIZE = 10;
private static final Insets WEST_INSETS = new Insets(5, 5, 5, 10);
private static final Insets EAST_INSETS = new Insets(5, 10, 5, 5);
private static final int EB_GAP = 5;
private Map<String, JTextField> textFieldMap = new HashMap<String, JTextField>();
public JPanel getConfigFooPanel() {
JPanel textFieldPanel = new JPanel(new GridBagLayout());
for (int i = 0; i < LABEL_TEXTS.length; i++) {
addTextAndField(textFieldPanel, LABEL_TEXTS[i], i);
}
int blVertGap = 20;
JPanel borderLayoutPanel = new JPanel(new BorderLayout(0, blVertGap));
borderLayoutPanel.setBorder(BorderFactory.createEmptyBorder(EB_GAP, EB_GAP,
EB_GAP, EB_GAP));
JLabel titleLabel = new JLabel(TITLE, JLabel.CENTER);
borderLayoutPanel.add(titleLabel, BorderLayout.PAGE_START);
borderLayoutPanel.add(textFieldPanel, BorderLayout.CENTER);
JPanel outerWrapperFlowPanel = new JPanel();
outerWrapperFlowPanel.add(borderLayoutPanel);
return outerWrapperFlowPanel;
}
public String getFieldText(String labelText) {
JTextField field = textFieldMap.get(labelText);
if (field == null) {
return ""; // ?? throw exception
} else {
return field.getText();
}
}
private void addTextAndField(JPanel panel, String text, int i) {
JLabel label = new JLabel(text, JLabel.LEFT);
JTextField textField = new JTextField(TEXTFIELD_SIZE);
textFieldMap.put(text, textField);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = i;
gbc.gridwidth = 1;
gbc.gridheight = 1;
gbc.weightx = 1.0;
gbc.weighty = 1.0;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.anchor = GridBagConstraints.WEST;
gbc.insets = WEST_INSETS;
panel.add(label, gbc);
gbc.gridx = 1;
gbc.anchor = GridBagConstraints.EAST;
gbc.insets = EAST_INSETS;
panel.add(textField, gbc);
}
private static void createAndShowGui() {
JFrame frame = new JFrame("LayoutFoo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new LayoutFoo().getConfigFooPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Same Question, different context
It seems I was too hasty in my accepting before, since the problem is still there. The problem? JLabel takes the liberty of expanding its parent panel when content is added to it.
It's time for reproducing it per "Hovercraft full of eels"-ses suggestion, and here it is:
import java.awt.*;
import javax.swing.*;
public class TestLabel {
public static void main(String[] args) {
// Var inits
JFrame frame;
JPanel panel;
JLabel label;
Container pane;
GridBagConstraints gbc = new GridBagConstraints();
// Frame, content pane, layout inits
frame = new JFrame("Label Tester");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pane = frame.getContentPane();
pane.setLayout(new GridBagLayout());
gbc.weighty = 1;
gbc.fill = GridBagConstraints.BOTH;
// Add panels (note gbc weighty and fill carries over all instances)
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 0;
panel = new JPanel();
panel.setBackground(Color.GREEN);
frame.add(panel,gbc);
label = new JLabel("THE PANEL IS NOW DISTORTED TO FIT THIS LABEL WHY IS THIS HAPPENING");
//label = new JLabel("");
label.setOpaque(true);
label.setBackground(Color.WHITE);
panel.add(label);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 0;
panel = new JPanel();
panel.setBackground(Color.RED);
frame.add(panel,gbc);
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.BLUE);
frame.add(panel,gbc);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.YELLOW);
frame.add(panel,gbc);
frame.pack();
frame.setSize(800,600);
frame.setVisible(true);
}
}
Results:
As you can see, the green panel is forced wider and throws off my whole layout when text (or, in the original question, and icon) is added to it. I want my layout to remain the same weights, regardless of the content. The reason this came up is because I'm trying to add a scaled image as an icon to the label, as seen in the original question.
Incidentally, setPreferredSize() doesn't seem to work.
Is there a way to fix this?
Original Question
My JLabel element expands dramatically when I add an Icon to it. Why is this happening? Here's the applicable portion of the code:
// Show label and BG color
redLabel.setBackground(Color.RED);
redLabel.setOpaque(true);
// Grab stretched image (already loaded elsewhere in the code) and turn to icon
Img = Img.getScaledInstance(redLabel.getWidth(),12,Image.SCALE_REPLICATE);
ImageIcon icon = new ImageIcon(Img);
// This line throws everything off!
//It's commented out in the first pic, and included in the second.
redLabel.setIcon(icon);
As you can see from the first pic, I've got a label (in red) of width W. What I'm trying to do is stretch my icon to width W and put it in the label.
When I do this, the label expands (by exactly 50 pixels, I think) and also squeezes over the left edge (green). Does anyone have any idea why this is happening?
I've tried several things that are too verbose to explain but can't find the problem :-/
Your component expands because it allocates the necessary space for its Icon.
public class JLabelDemo {
private static BufferedImage bi;
public static void main(String[] args) throws IOException{
loadImage();
SwingUtilities.invokeLater(new Runnable(){
#Override
public void run() {
createAndShowGUI();
}
});
}
private static void loadImage() throws IOException{
bi = ImageIO.read(JLabelDemo.class.getResource("../resource/forever-alone.jpg"));
}
private static void createAndShowGUI(){
final JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel panel = new JPanel();
panel.setBackground(Color.YELLOW);
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
final JLabel emptyLabel = new JLabel();
final JLabel textLabel = new JLabel("This label has text only");
final JLabel textAndImageLabel = new JLabel("This label has text and image");
textAndImageLabel.setIcon(new ImageIcon(bi));
panel.add(emptyLabel);
panel.add(textLabel);
panel.add(textAndImageLabel);
frame.add(panel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
System.out.println("Empty label dimensions - " + emptyLabel.getSize());
System.out.println("Text only label dimensions - " + textLabel.getSize());
System.out.println("Image width: " + bi.getWidth() + ", Image height: " + bi.getHeight());
System.out.println("Text and image label dimensions - " +textAndImageLabel.getSize());
}
}
The following is outputted to console:
Empty label dimensions - java.awt.Dimension[width=0,height=0]
Text only label dimensions - java.awt.Dimension[width=129,height=16]
Image width: 194, Image height: 180
Text and image label dimensions - java.awt.Dimension[width=363,height=180]
Consider using a JLayeredPane to add components in layers. There are trips and traps though when doing this in matters of opacity, size and position of components added.
For example,
import java.awt.*;
import javax.swing.*;
public class TestLabel {
private static final Dimension SIZE = new Dimension(800, 600);
public static void main(String[] args) {
GridBagConstraints gbc = new GridBagConstraints();
JPanel defaultPane = new JPanel();
defaultPane.setLayout(new GridBagLayout());
gbc.weighty = 1;
gbc.fill = GridBagConstraints.BOTH;
// Add panels (note gbc weighty and fill carries over all instances)
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 0;
JPanel panel = new JPanel();
panel.setBackground(Color.GREEN);
defaultPane.add(panel, gbc);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 0;
panel = new JPanel();
panel.setBackground(Color.RED);
defaultPane.add(panel, gbc);
gbc.weightx = 0.3;
gbc.gridx = 0;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.BLUE);
defaultPane.add(panel, gbc);
gbc.weightx = 0.7;
gbc.gridx = 1;
gbc.gridy = 1;
panel = new JPanel();
panel.setBackground(Color.YELLOW);
defaultPane.add(panel, gbc);
defaultPane.setSize(SIZE);
JLabel label = new JLabel("THE PANEL IS NOW DISTORTED TO FIT THIS LABEL WHY IS THIS HAPPENING");
label.setOpaque(true);
label.setBackground(Color.WHITE);
JPanel northPalettePanel = new JPanel();
northPalettePanel.setOpaque(false);
northPalettePanel.add(label);
JPanel palettePanel = new JPanel(new BorderLayout());
palettePanel.setOpaque(false);
palettePanel.setSize(SIZE);
palettePanel.setLocation(0, 0);
palettePanel.add(northPalettePanel, BorderLayout.NORTH);
JLayeredPane layeredPane = new JLayeredPane();
layeredPane.setPreferredSize(SIZE);
layeredPane.add(defaultPane, JLayeredPane.DEFAULT_LAYER);
layeredPane.add(palettePanel, JLayeredPane.PALETTE_LAYER);
JFrame frame = new JFrame("Label Tester");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(layeredPane, BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}
Java swing is pretty old for me but if I remember well, setting a preferred size (setPreferredSize()) sometime solve these kind of problem ... Also try top lay with setMaximumSize and setMinimumSize.
You can maybe find more information in java documentation:
http://download.oracle.com/javase/tutorial/uiswing/layout/using.html#sizealignment
Regards!