Java-看不到JRadioButtons

Question

I am a beginner and I was practicing JRadioButtons. I realised that I can't see my JRadioButtons if I'll not set my layout as 'FlowLayout()' . I want to set the location of the buttons by myself.

I posted my code below, can anyone help me what am I doing wrong ?

Thanks!

private JFrame frame;
private JPanel panel;
private JRadioButton btn1, btn2;


public JBButtons() {

    form();
    radioButtons();

    frame.add(panel);
    frame.setVisible(true);
}

public void form(){

    frame = new JFrame("Frame");
    frame.setSize(400, 200);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    panel = new JPanel();
    panel.setLayout(null);
    //panel.setLayout(new FlowLayout());
}


public void radioButtons() {

    ButtonGroup group = new ButtonGroup();

    btn1 = new JRadioButton("btn1");
    btn1.setSelected(true);
    btn1.setLocation(50, 50);

    btn2 = new JRadioButton("btn2");
    btn2.setLocation(50, 70);

    group.add(btn1);
    group.add(btn2);

    panel.add(btn1);
    panel.add(btn2);

}

public static void main(String[] args) {

    new JBButtons();
}

Answer 1

The issue with absolute positioning or null layout is - it requires you to set the sizes of all your components, otherwise they will stay their default zero-size and won't show up. Better use a layout manager - https://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html

Answer 2

Add this part of the code when adding the RadioButton to the panel, use the property .setBounds(x, y, width, heigth) .

panel.add(btn1);
btn1.setBounds(90, 59, 93, 23);
panel.add(btn2);
btn2.setBounds(180, 60, 93, 23);