Java align JLabel in center of JPanel

问题

I have a bar at the top of my application that has a number of buttons either side of a JLabel. The button's visibility is dependent upon the current task a user is carrying out and one of the button's text may also change depending on the current state.

What I would like to do is have a number of buttons stick to the left of the JPanel, the JLabel's center to be in the very center of the JPanel and the rest of the buttons to be to the right of the JPanel.

So far I have managed to get the buttons sticking to the left and the right using various methods and layout managers but I cannot get the JLabel's center to be in the dead center of the JPanel. The best I have managed to get is the label near enough to the center but it would then move around as the buttons are set to visible or their text changes.

Is it possible to force the JLabel to remain dead center?

Note: the buttons will never become big enough to meet either edge of the JLabel, so that is not a problem.

回答1:

As I see it you need the label to be displayed at its preferred size and then you need a left and right panel to equally fill the remaining space available in the window.

You can use the Relative Layout class.

import java.awt.*;
import javax.swing.*;

public class RelativeSSCCE extends JPanel
{
    public RelativeSSCCE()
    {
        JPanel left = new JPanel( new FlowLayout(FlowLayout.LEFT) );
        left.add( new JButton("L1") );
        left.add( new JButton("L2") );
        left.add( new JButton("L3") );

        JLabel center = new JLabel("Centered");

        JPanel right = new JPanel( new FlowLayout(FlowLayout.RIGHT) );
        right.add( new JButton("Right1") );
        right.add( new JButton("Right2") );
        right.add( new JButton("Right3") );

        // choose your layout manager here

        setLayout( new RelativeLayout() );
        Float ratio = new Float(1);
        add(left, ratio);
        add(center);
        add(right, ratio);
    }

    private static void createAndShowUI()
    {
        JFrame frame = new JFrame("Basic RelativeSSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add( new RelativeSSCCE() );
        frame.setSize(600, 100);
        frame.setLocationRelativeTo( null );
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowUI();
            }
        });
    }
}

回答2:

You could also use a BoxLayout, with X_AXIS layout, and add to the container

Edit: Here's an example

panel.setLayout(new BoxLayout(panel, BoxLayout.X_AXIS));
panel.add(Box.createHorizontalGlue());
panel.add(innerPanel);
panel.add(Box.createHorizontalGlue());

回答3:

Use BorderLayout. Add the JLabel with the BorderLayout.CENTER constraint and add a pair of JPanels with the BorderLayout.EAST and BorderLayout.WEST constraints. Add your additional buttons to the appropriate JPanel.

To have the text appear centered, you also need to set the Label's horizontalAlignment to JLabel.CENTER.

回答4:

setAlignmentX(java.awt.Component.CENTER_ALIGNMENT)

and

setAlignmentY(java.awt.Component.CENTER_ALIGNMENT)

may help if used with the elements which have to be centered, e.g. JPanel

回答5:

may be I`m necroposting, but setAlignmentX(java.awt.Component.CENTER_ALIGNMENT) and setAlignmentY(java.awt.Component.CENTER_ALIGNMENT) may help...

来源：https://stackoverflow.com/questions/5345609/java-align-jlabel-in-center-of-jpanel

标签

java

swing

jpanel

jlabel

layout-manager