How to Change the Size of the Font of a Jlabel to Take the Maximum Size

How to change the size of the font of a JLabel to take the maximum size

Not the most pretty code, but the following will pick an appropriate font size for a JLabel called label such that the text inside will fit the interior as much as possible without overflowing the label:

Font labelFont = label.getFont();
String labelText = label.getText();

int stringWidth = label.getFontMetrics(labelFont).stringWidth(labelText);
int componentWidth = label.getWidth();

// Find out how much the font can grow in width.
double widthRatio = (double)componentWidth / (double)stringWidth;

int newFontSize = (int)(labelFont.getSize() * widthRatio);
int componentHeight = label.getHeight();

// Pick a new font size so it will not be larger than the height of label.
int fontSizeToUse = Math.min(newFontSize, componentHeight);

// Set the label's font size to the newly determined size.
label.setFont(new Font(labelFont.getName(), Font.PLAIN, fontSizeToUse));

Basically, the code looks at how much space the text in the JLabel takes up by using the FontMetrics object, and then uses that information to determine the largest font size that can be used without overflowing the text from the JLabel.

The above code can be inserted into perhaps the paint method of the JFrame which holds the JLabel, or some method which will be invoked when the font size needs to be changed.

The following is an screenshot of the above code in action:

_{(source: coobird.net)}

Change JLabel Font size

You are calling the wrong deriveFont method.

The parameter in deriveFont(int) is the style (bold, italic, etc.). The method you are looking for is deriveFont(float).

In your case, the only change you need to make is intro.setFont(intro.getFont().deriveFont(64.0f));.

Here's a short code example that does display a label with font size 64:

JFrame frame = new JFrame ("Test");
JLabel label = new JLabel ("Font Test");
label.setFont (label.getFont ().deriveFont (64.0f));
frame.getContentPane ().add (label);
frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
frame.pack ();
frame.setVisible (true);

How to change JLabel's size when the font size is changed?

Don't use setPreferredSize, you've just removed all the calculations that the label uses to calculate the size it would like to be.

Avoid using null layouts, pixel perfect layouts are an illusion within modern ui design. There are too many factors which affect the individual size of components, none of which you can control. Swing was designed to work with layout managers at the core, discarding these will lead to no end of issues and problems that you will spend more and more time trying to rectify

Make use of appropriate layouts. The important thing here is, no one layout will ever do everything you want. You will need to learn to take advantage of the each layout's strengths (and weaknesses) and use them to your advantage. This is what is commonly known as "compound layouts". Have a look at Laying Out Components Within a Container for more details and ideas

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JLabel label;
        private JSlider slider;

        public TestPane() {
            label = new JLabel("Look, no hands!");
            setLayout(new BorderLayout());
            JPanel panel = new JPanel(new GridBagLayout());
            panel.add(label);

            add(panel);

            slider = new JSlider(8, 96);
            add(slider, BorderLayout.SOUTH);

            slider.addChangeListener(new ChangeListener() {
                @Override
                public void stateChanged(ChangeEvent e) {
                    Font font = label.getFont();
                    font = font.deriveFont((float)slider.getValue());
                    label.setFont(font);
                }
            });
            slider.setValue(8);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

    }

}

JLabel is surprising proficient, changing the font (text/icon) will automatically cause it to invalidate the layout and request a repaint all by itself...

I want to decrease the font size if text doesn't fit in JLabel

Adapted from an answer on the question you referred to:

void setTextFit(JLabel label, String text) {
    Font originalFont = (Font)label.getClientProperty("originalfont"); // Get the original Font from client properties
    if (originalFont == null) { // First time we call it: add it
        originalFont = label.getFont();
        label.putClientProperty("originalfont", originalFont);
    }

    int stringWidth = label.getFontMetrics(originalFont).stringWidth(text);
    int componentWidth = label.getWidth();

    if (stringWidth > componentWidth) { // Resize only if needed
        // Find out how much the font can shrink in width.
        double widthRatio = (double)componentWidth / (double)stringWidth;

        int newFontSize = (int)Math.floor(originalFont.getSize() * widthRatio); // Keep the minimum size

        // Set the label's font size to the newly determined size.
        label.setFont(new Font(originalFont.getName(), originalFont.getStyle(), newFontSize));
    } else
        label.setFont(originalFont); // Text fits, do not change font size

    label.setText(text);
}

When you'll display a number that would fit, you should reset the Font back to its original (see the else part).

EDIT: If you can't/don't want to keep a reference to the original Font, you can save it as a "client property" (see the first lines).

How to change the font size of a JLabel that is in a panel.add(new JLabel());

It's a strange way to access a JLabel but this may work ...

Component[] components = examplePanel.getComponents();

for (Component singleComponent : components) {
   if (singleComponent instanceof JLabel) {
       JLabel label = (JLabel) singleComponent;

       if ("this is an example".equals(label.getText()) {
              label.setFont(new Font("", Font.PLAIN, 20));
       }
   }
}

Another way, create a new class for those JLabels that you want to change.

public class JMyFontLabel extends JLabel {
  boolean applyFontChange = false;

  public JMyFontLabel(String text, boolean applyFontChange) {
         super(text);
         this.applyFontChange = applyFontChange;
  }

  // get / set methods for applyFontChange.
} 

// Method to apply font
public void setMyFont(JPanel examplePanel, Font myFont) {
   Component[] components = examplePanel.getComponents();

   for (Component singleComponent : components) {

   if (singleComponent instanceof JMyFontLabel) {
       JMyFontLabel label = (JMyFontLabel) singleComponent;

       if (label.isApplyFontChange()) {
          label.setFont(myFont);
       }
   }
}

On label creation, set applyFontChange

   examplePanel.add(new JMyFontLabel("Name", true));

How to change JLabel font size to fill JPanel free space while resizing?

ok, here is answer.

Let's take the code from here: How to change the size of the font of a JLabel to take the maximum size, answer from coobird

int componentWidth = label.getWidth();

We need to get width from the JFrame component, NOT from JLabel, because the code will no let opportunity to change size for the JLabel.

this will fix it:

int componentWidth = this.getWidth()-20; // '20' - according width of Jlabel to JFrame

Resize JLabel text size with collections in Java Swing

As I understand your question, your answer is similar to this below said thread first answer, just follow this link -

How to change the size of the font of a JLabel to take the maximum size

Font labelFont = label.getFont();
String labelText = label.getText();

int stringWidth = label.getFontMetrics(labelFont).stringWidth(labelText);
int componentWidth = label.getWidth();

// Find out how much the font can grow in width.
double widthRatio = (double)componentWidth / (double)stringWidth;

int newFontSize = (int)(labelFont.getSize() * widthRatio);
int componentHeight = label.getHeight();

// Pick a new font size so it will not be larger than the height of label.
int fontSizeToUse = Math.min(newFontSize, componentHeight);

// Set the label's font size to the newly determined size.
label.setFont(new Font(labelFont.getName(), Font.PLAIN, fontSizeToUse));

hope this will help you, thanks.

How to set fix size of jlabel?

You can set a fixed the size by setting the minimum, preferred and maximum size:

setMinimumSize(width, height);
setPreferredSize(width, height);
setMaximumSize(width, height);

As the Link from MadProgrammer, you need to override these methods, not using them from outside, based on the reasons mentioned in this link.

Set size for jLabel in swing

setPreferredSize changes really the size of the label you should just try to draw it border using setBorder method to verify the new size, but the font size is not changed, if you want to have big font try to call setFont and set the new font size, here some code to start with:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.border.LineBorder;

public class Test {
    public static void main(String[] args) {
        JFrame t = new JFrame();
        t.setBounds(100, 100, 500, 400);
        JLabel l = new JLabel("Hello");
        // new font size is 20
        l.setFont(new Font(l.getFont().getName(), l.getFont().getStyle(), 20));
        // draw label border to verify the new label size
        l.setBorder(new LineBorder(Color.BLACK));
        // change label size
        l.setPreferredSize(new Dimension(200, 200));
        t.getContentPane().setLayout(new FlowLayout());
        t.add(l);
        t.setVisible(true);
    }
}

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