Change the way JRadioButtons displayed on JPanel

Question

I have a JPanel, and I want to add JRadioButtons to it, this is the code I tried :

private void populateQuestionnaire(Question question){
            buttonGroup = new ButtonGroup();
            for(Choix c : question.getListChoix()) {
                radioButton = new JRadioButton(c.getChoixLibelle());
                buttonGroup.add(radioButton);
                jPanel1.add(radioButton);

            }
            jPanel1.revalidate();   
            jPanel1.repaint();
    }

And I have the layout of JPanel is FlowLayout.

This is how the JRadioButtons displayed :

enter image description here

I want JRadioButtons to be added one below the other and to be centered in the JPanel.

See [this answer](http://stackoverflow.com/a/20938621/2587435). Its pretty much what you're looking for. — Paul Samsotha, Jan 05 '14 at 21:08

score 3 · Answer 1 · answered Jan 05 '14 at 21:05

Instead of using a FlowLayout, which lays out items left to right and wraps appropriately, you can use a BoxLayout, which allows you to specify laying out items either horizontally or vertically.

You can set the LayoutManager for your JPanel at construction:

JPanel jpanel1 = new JPanel(new BoxLayout(parentComponent, BoxLayout.Y_AXIS));

Andrew Gies · Accepted Answer · 2014-01-05T22:36:57.670

BoxLayout is great for stacking elements on top of each other. Consider this code:

public class MyFrame extends JFrame {

    public MyFrame() {
        ButtonGroup bg = new ButtonGroup();
        JRadioButton b1 = new JRadioButton("My Button 1");
        JRadioButton b2 = new JRadioButton("My Button 2");
        bg.add(b1);
        bg.add(b2);

        BoxLayout bl = new BoxLayout(this.getContentPane(), BoxLayout.Y_AXIS);
        this.setLayout(bl);

        b1.setAlignmentX(CENTER_ALIGNMENT);
        b2.setAlignmentX(CENTER_ALIGNMENT);

        this.add(b1);
        this.add(b2);
    }

}

Which makes, when instantiated and shown, the following window:

Screenshot

Now let's look at how this code works:

Consider this code:

ButtonGroup bg = new ButtonGroup();
JRadioButton b1 = new JRadioButton("My Button 1");
JRadioButton b2 = new JRadioButton("My Button 2");
bg.add(b1);
bg.add(b2);

This code does the same thing you were doing before, only a little simpler for example's sake. It creates a button group and two JRadioButtons, then adds the buttons to the button group. Now here is when it gets interesting.

Next, consider this code:

BoxLayout bl = new BoxLayout(this.getContentPane(), BoxLayout.Y_AXIS);
this.setLayout(bl);

The first line creates a new BoxLayout with the following parameters:

1 The container which it is laying out. (It needs this because it can't be shared.)

2 The axis which it should be laying out components. (You want Y-AXIS for your case.)

The second line set's the JFrame's contentPane's layout to the BoxLayout you just created.

Finally, consider this code:

b1.setAlignmentX(CENTER_ALIGNMENT);
b2.setAlignmentX(CENTER_ALIGNMENT);

this.add(b1);
this.add(b2);

This sets the alignment of the two radio buttons so that their centers will be aligned to each other and to the center of the frame. Then it adds them to the frame's content pane.

Hope this helped!

Note: The reason I used this.getContentPane() while constructing the BoxLayout instead of just using this is because when working with JFrames commands like add() and setLayout() get redirected to the frame's content pane. So if we were to use this in the constructor, when we called this.setLayout(bl) we really would be calling this.getContentPane().setLayout(bl). But, we just told the BoxLayout it'll be laying out the frame, not it's content pane, so you'll get an exception saying that the BoxLayout can't be shared. To correct the error, we just need to realise that we are actually working with the content pane through the frame's methods, and update the BoxLayout's constructor accordingly to let it know what it really is laying out.

Change the way JRadioButtons displayed on JPanel

2 Answers2