Java Swing面板/按钮布局

Question

I am creating a simple calculator GUI. Also,I am having an issue with resizing the help and exit button to about the size of the numbers button. I know I am doing something wrong with GridLayout , but not sure what it is.The code has no issues.

This is what it looks like:

public static final int WIDTH = 350;
public static final int HEIGHT = 500;
public static final int NUMBER_OF_CHAR = 4;

private JTextField single;
private JTextField equation;
boolean setBlank = false;
Double result;
String resultStr;
String verifyAction = "";
public Calculator()
{
    super("Calculator");
    setSize(WIDTH, HEIGHT);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLayout(new GridLayout(3,0,0,0));
    JPanel top = new JPanel();
    top.setLayout(new GridLayout(1,2));

    JPanel mid = new JPanel();
    mid.setLayout(new GridLayout(2,1));

    JPanel bottom = new JPanel();
    bottom.setLayout(new GridLayout(4,4));
    //TOP
    JButton exit = new JButton("Exit");
    exit.addActionListener(this);
    top.add(exit);

    JButton help = new JButton("Help");

    help.addActionListener(this);
    top.add(help);
    //MID
    single = new JTextField(NUMBER_OF_CHAR);
    mid.add(single);
    equation = new JTextField(NUMBER_OF_CHAR);
    mid.add(equation);
    //BOTTOM
    String [] key = {"7","8","9","+","4","5","6","","1","2","3","/","0",".","clear","="};
    for(int i = 0 ; i < key.length;i++)
    {
        JButton button = new JButton(key[i]);
        button.addActionListener(this);
        bottom.add(button);
    }
    add(top,BorderLayout.NORTH);
    add(mid,BorderLayout.CENTER);
    add(bottom,BorderLayout.SOUTH);
}

Answer 1

This is a main problem: setSize(WIDTH, HEIGHT); . Don't do this as this can cause components that you don't want to have re-size do so. Instead all the components to size to their own preferred sizes by calling pack() on the top window, the JFrame, after adding all components. Again this will let the GUI size itself.

Don't use GridLayout for the JPanel, but rather leave it BorderLayout, and play with your GUI component fonts. For example

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

public class Calculator extends JFrame implements ActionListener {
    public static final int WIDTH = 350;
    public static final int HEIGHT = 500;
    public static final int NUMBER_OF_CHAR = 4;
    public static final Font MY_FONT = new Font(Font.DIALOG, Font.BOLD, 24);

    private JTextField single;
    private JTextField equation;
    boolean setBlank = false;
    Double result;
    String resultStr;
    String verifyAction = "";

    public Calculator() {
        super("Calculator");
        // setSize(WIDTH, HEIGHT);  // !! No ***************
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // setLayout(new GridLayout(3, 0, 0, 0)); // !! No ***************
        JPanel top = new JPanel();
        top.setLayout(new GridLayout(1, 2));

        JPanel mid = new JPanel();
        mid.setLayout(new GridLayout(2, 1));

        JPanel bottom = new JPanel();
        bottom.setLayout(new GridLayout(4, 4));
        // TOP
        JButton exit = new JButton("Exit");
        exit.setFont(MY_FONT);
        exit.addActionListener(this);
        top.add(exit);

        JButton help = new JButton("Help");
        help.setFont(MY_FONT);

        help.addActionListener(this);
        top.add(help);
        // MID
        single = new JTextField(NUMBER_OF_CHAR);
        single.setFont(MY_FONT);
        mid.add(single);
        equation = new JTextField(NUMBER_OF_CHAR);
        equation.setFont(MY_FONT);
        mid.add(equation);
        // BOTTOM
        String[] key = { "7", "8", "9", "+", "4", "5", "6", "", "1", "2", "3", "/", "0", ".", "clear", "=" };
        for (int i = 0; i < key.length; i++) {
            JButton button = new JButton(key[i]);
            button.setFont(MY_FONT);
            button.addActionListener(this);
            bottom.add(button);
        }
        add(top, BorderLayout.NORTH);
        add(mid, BorderLayout.CENTER);
        add(bottom, BorderLayout.SOUTH);

        pack();
        setLocationRelativeTo(null);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub

    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            new Calculator().setVisible(true);
            ;
        });
    }
}