Positioning JLabels

Question

Hey,
I'm trying to learn Swing applications and I've run into a bit of trouble positioning my "Hello World" label on the screen. I've created a JFrame that is 640x480 in size and I want to move my label to a specific x,y within the frame. I've tried using setLocation and setBounds with no luck. The label stays stuck vertically centered on the left side of the screen. How do I move this label around?
Mike

Answer 1

You need to read on the layout managers. For instance JFrame contentPanes use the BorderLayout as the default layout manager while JPanels use FlowLayout as the default managers. There are two ways to work here: 1) work with the the appropriate layout manager to place your JLabel in a position that will remain correct even if the JFrame is resized, or 2) set the contentPane's layout to null and place your JLabel by absolute positioning (i.e., setBounds or something similar). If you do the latter, you will have to set the size of the jlabel too (setBounds does this). I recommend the former technique over the latter.
For instance this adds a JLabel to a JFrame (via a JPanel) by the first method: the null layout with absolute positioning and sizing of the JLabel by calling its setBounds method:
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
class HelloWorldFrame
    // the JPanel that will hold our JLabel
    private JPanel mainPanel = new JPanel();
    public HelloWorldFrame()
        mainPanel.setPreferredSize(new Dimension(640, 480));
        mainPanel.setLayout(null); // use no layout manager
        JLabel helloWorldLabel = new JLabel("Hello World");
        // set the bounds: both the location x, y, and the size width, height
        helloWorldLabel.setBounds(20, 400, 100, 24);
        // so we can see the exact size of the JLabel
        helloWorldLabel.setBorder(BorderFactory.createLineBorder(Color.blue, 4));
        mainPanel.add(helloWorldLabel); // add it to the JPanel
    public JPanel getMainPanel()
        return mainPanel;
    private static void createAndShowUI()
        // create a JFrame
        JFrame frame = new JFrame("HelloWorldFrame");
        // add our JPanel to this JFrame
        frame.getContentPane().add(new HelloWorldFrame().getMainPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    // call swing in a thread-safe manner
    public static void main(String[] args)
        java.awt.EventQueue.invokeLater(new Runnable()
            public void run()
                createAndShowUI();
}And here I add the JLabel using the second technique: layout managers:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
class HelloWorldFrame2
    // the JPanel that will hold our JLabel
    private JPanel mainPanel = new JPanel();
    public HelloWorldFrame2()
        mainPanel.setPreferredSize(new Dimension(640, 480));
        mainPanel.setLayout(new BorderLayout());
        mainPanel.setBorder(BorderFactory.createEmptyBorder(0, 20, 56, 0));
        JLabel helloWorldLabel = new JLabel("Hello World");
        // so we can see the exact size of the JLabel
        helloWorldLabel.setBorder(BorderFactory.createLineBorder(Color.blue, 4));
        JPanel labelPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));
        labelPanel.add(helloWorldLabel);
        mainPanel.add(labelPanel, BorderLayout.SOUTH); // add it to the JPanel
    public JPanel getMainPanel()
        return mainPanel;
    private static void createAndShowUI()
        // create a JFrame
        JFrame frame = new JFrame("HelloWorldFrame2");
        // add our JPanel to this JFrame
        frame.getContentPane().add(new HelloWorldFrame2().getMainPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    // call swing in a thread-safe manner
    public static void main(String[] args)
        java.awt.EventQueue.invokeLater(new Runnable()
            public void run()
                createAndShowUI();
}Edited by: Encephalopathic on Feb 18, 2008 7:58 PM