Swing…添加JTextField使我的JPanel消失

Question

Having a strange problem. I'm learning Java Swing right now, and have a basic frame with a set size. I added buttons, and then radio buttons, and everything was fine. I add a JTextField and everything goes blank on the Frame until I manually resize it and then everything appears. I've tried messing around with Grids and GridBagConstraints and nothing seems to be helping, but I don't have a very good handle on working with those just yet. Everything is sized correctly I believe, but the box opens up blank and then when I change the size even by a single pixel in any direction, everything shows up fine.

Here is my code so far:

import javax.swing.*;

import java.awt.*;

public class Test {

    private JFrame f; //frame
    private JPanel p; //window
    private JButton b1; //button
    private JButton b2; //button
    private JButton b3; //button
    private JButton b4; //button
    private JRadioButton rad1;
    private JRadioButton rad2;
    private String radBut1 = "Checking";
    private String radBut2 = "Savings";
    private JTextField textField;


public Test(){

    gui();

}

public void gui(){      

    f = new JFrame("ATM Machine");
    f.setVisible(true);
    f.setSize(350,200);
    f.setLocationRelativeTo(null);
    //f.setResizable(false);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    p = new JPanel();

    b1 = new JButton("Withdraw From");
    b2 = new JButton("Deposit To");
    b3 = new JButton("Transfer To");
    b4 = new JButton("Balance Of");

    b1.setPreferredSize(new Dimension(150,25));
    b2.setPreferredSize(new Dimension(150,25));
    b3.setPreferredSize(new Dimension(150,25));
    b4.setPreferredSize(new Dimension(150,25));

    p.add(b1);
    p.add(b2);
    p.add(b3);
    p.add(b4);

    rad1 = new JRadioButton(radBut1);
    rad2 = new JRadioButton(radBut2);






    ButtonGroup radioGroup = new ButtonGroup();
    radioGroup.add(rad1);
    radioGroup.add(rad2);

    p.add(rad1);
    p.add(rad2);

    textField = new JTextField(25);

    p.add(textField);


    f.add(p);




}

public static void main(String[] args) {

    new Test();


}

}

So basically it needs to look like 2 buttons on top, 2 buttons underneath those buttons, 2 radio buttons under those, and then finally the TextField under the radio buttons.

I would appreciate any help.

Thanks!

Answer 1

Components should be added to the frame BEFORE making the frame visible.

f = new JFrame("ATM Machine");
//f.setVisible(true);
...
f.add(p);
f.setVisible(true);

and have a basic frame with a set size.

Don't set the size of the frame. Let Swing determine the size of each component and the size of the frame. So really the code should be:

f.add(p);
f.pack();
f.setVisible(true);

Don't set the preferredSize() of your buttons. If you want all the buttons to be the same size, then use a GridLayout on a separate panel:

JPanel buttons = new JPanel( new GridLayout(0, 4) );
buttons.add(b1);
buttons.add(b2);
...

Then you add the buttons panel to the frame.

Also, you need to change the layout manager. Right now you are using a FlowLayout and the layout only appears to work correctly. If you resize the frame components will flow to another line. Maybe you need to use a BoxLayout .

Read the Swing tutorial on Using Layout Manager for more information.