如何在Java Swing中摆脱JPanel中的额外填充

Question

I'm working on a calculator that's based off of windows 10 calculator. I like the look and feel of it and I'm challenging myself to this project to test how well I know Java. But after I got the main design finished I noticed extra padding around my window. After debugging and figuring it out, I found out that the extra padding comes my my three JPanels (topPanel, middlePanel, bottomPanel) inside of my main JPanel (mainPanel). I'm using a gridBagLayout and have all insets set to 0 for top, bottom, left, and right. And I'm not sure how to get rid of the extra padding. This is my full code from my Calculator class

package javacalculator.calculator;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.BorderFactory;

import javax.swing.border.Border;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.text.Caret;
import javax.swing.text.DefaultCaret;

public class Calculator {
    private final String NAME = "Calculator";

    private JFrame frame;
    private JPanel mainPanel, topPanel, middlePanel, bottomPanel;
    private JTextField storedData;
    private JTextField data;
    private Caret caret;
    private Font font;
    private Font font2;
    private Font font3;
    private Font font4;
    private Color color;
    private JButton zero, one, two, three, four, five, six, seven, eight, nine;
    private JButton plus, minus, multiply, divide, equals;
    private JButton negative, decimal;
    private JButton ce, c, backspace;
    private JButton percent, squareRoot, squared, divideFrom1;
    private JButton mc, mr, mplus, mminus, ms, mh;

    public Calculator() {
        frame = new JFrame(NAME);
        mainPanel = new JPanel();
        topPanel = new JPanel();
        middlePanel = new JPanel();
        bottomPanel = new JPanel();

        storedData = new JTextField();
        data = new JTextField();
        caret = new DefaultCaret() {
            @Override
            public void paint(Graphics g) {

            }

            @Override
            public boolean isVisible() {
                return false;
            }

            @Override
            public boolean isSelectionVisible() {
                return false;
            }
        };
        font = new Font("Sans-Serif", Font.BOLD, 30);
        font2 = new Font("Sans-Serif", Font.PLAIN, 20);
        font3 = new Font("Sans-Serif", Font.PLAIN, 15);
        font4 = new Font("Sans-Serif", Font.PLAIN, 13);
        color = new Color(238, 238, 238);

        mc = new JButton("MC");
        mr = new JButton("MR");
        mplus = new JButton("M+");
        mminus = new JButton("M-");
        ms = new JButton("MS");
        mh = new JButton("MH");

        percent = new JButton("%");
        squareRoot = new JButton("SQRT");
        squared = new JButton("x^2");
        divideFrom1 = new JButton("1/x");

        ce = new JButton("CE");
        c = new JButton("C");
        backspace = new JButton("<=");

        plus = new JButton("+");
        minus = new JButton("-");
        multiply = new JButton("X");
        divide = new JButton("/");
        equals = new JButton("=");

        decimal = new JButton(".");
        negative = new JButton("+/-");

        zero = new JButton("0");
        one = new JButton("1");
        two = new JButton("2");
        three = new JButton("3");
        four = new JButton("4");
        five = new JButton("5");
        six = new JButton("6");
        seven = new JButton("7");
        eight = new JButton("8");
        nine = new JButton("9");

        Init();
    }

    private void Init() {
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        ConfigureComponents();

        AddComponent(topPanel, storedData, 0, 0, 4, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(topPanel, data, 0, 1, 4, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(middlePanel, mc, 0, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(middlePanel, mr, 1, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(middlePanel, mplus, 2, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(middlePanel, mminus, 3, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(middlePanel, ms, 4, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(middlePanel, mh, 5, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(bottomPanel, percent, 0, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, squareRoot, 1, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, squared, 2, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, divideFrom1, 3, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(bottomPanel, ce, 0, 1, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, c, 1, 1, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, backspace, 2, 1, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, divide, 3, 1, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(bottomPanel, seven, 0, 2, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, eight, 1, 2, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, nine, 2, 2, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, multiply, 3, 2, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(bottomPanel, four, 0, 3, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, five, 1, 3, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, six, 2, 3, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, minus, 3, 3, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(bottomPanel, one, 0, 4, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, two, 1, 4, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, three, 2, 4, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, plus, 3, 4, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(bottomPanel, negative, 0, 5, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, zero, 1, 5, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, decimal, 2, 5, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(bottomPanel, equals, 3, 5, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        AddComponent(mainPanel, topPanel, 0, 0, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(mainPanel, middlePanel, 0, 1, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);
        AddComponent(mainPanel, bottomPanel, 0, 2, 1, 1, GridBagConstraints.CENTER, GridBagConstraints.NONE);

        frame.add(mainPanel);

        frame.pack();
        frame.setResizable(false);

        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    private void AddComponent(JPanel panel, JComponent component, int x, int y, int width, int height, int position, int stretch) {
        GridBagConstraints gbc = new GridBagConstraints();

        gbc.gridx = x;
        gbc.gridy = y;

        gbc.gridwidth = width;
        gbc.gridheight = height;

        gbc.weightx = 0;
        gbc.weighty = 0;

        gbc.anchor = position;
        gbc.fill = stretch;

        gbc.insets = new Insets(0, 0, 0, 0);

        panel.add(component, gbc);
    }

    private void ConfigureComponents() {
        mainPanel.setLayout(new GridBagLayout());
        topPanel.setLayout(new GridBagLayout());
        middlePanel.setLayout(new GridBagLayout());
        bottomPanel.setLayout(new GridBagLayout());

        Dimension dim = new Dimension(77, 54);
        Dimension dim2 = new Dimension(dim.width * 4, dim.height);
        Dimension dim3 = new Dimension(dim.width * 4, dim.height / 2);
        Dimension dim4 = new Dimension(dim.width * 4 / 6, dim.height / 2);

        Border noBorder = BorderFactory.createEmptyBorder(0, 0, 0, 0);

        mainPanel.setBorder(noBorder);
        topPanel.setBorder(noBorder);
        middlePanel.setBorder(noBorder);
        bottomPanel.setBorder(noBorder);

        //TESTING
        topPanel.setBorder(BorderFactory.createLineBorder(Color.GREEN, 1, false));
        mainPanel.setBorder(BorderFactory.createLineBorder(Color.BLUE, 3, false));
        //END TESTING

        storedData.setPreferredSize(dim3);
        storedData.setFont(font3);
        storedData.setBackground(Color.WHITE);
        storedData.setHorizontalAlignment(JTextField.RIGHT);
        storedData.setBorder(noBorder);
        //TESTING
        storedData.setBorder(BorderFactory.createLineBorder(Color.RED, 1, false));
        //END TESTING
        storedData.setCaret(caret);
        storedData.setEditable(false);

        data.setPreferredSize(dim2);
        data.setFont(font);
        data.setBackground(Color.WHITE);
        data.setHorizontalAlignment(JTextField.RIGHT);
        data.setBorder(noBorder);
        data.setCaret(caret);
        data.setEditable(false);

        ConfigureComponent(mc, dim4, font4, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        mc.setPreferredSize(new Dimension(dim4.width + 1, dim4.height));
        ConfigureComponent(mr, dim4, font4, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(mplus, dim4, font4, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(mminus, dim4, font4, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(ms, dim4, font4, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(mh, dim4, font4, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        mh.setPreferredSize(new Dimension(dim4.width + 1, dim4.height));

        ConfigureComponent(percent, dim, font2, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(squareRoot, dim, font2, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(squared, dim, font2, Color.WHITE, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(divideFrom1, dim, font2, Color.WHITE, Color.BLACK, noBorder, true, false, false);

        ConfigureComponent(ce, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(c, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(backspace, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(divide, dim, font2, color, Color.BLACK, noBorder, true, false, false);

        ConfigureComponent(seven, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(eight, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(nine, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(multiply, dim, font2, color, Color.BLACK, noBorder, true, false, false);

        ConfigureComponent(four, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(five, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(six, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(minus, dim, font2, color, Color.BLACK, noBorder, true, false, false);

        ConfigureComponent(one, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(two, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(three, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(plus, dim, font2, color, Color.BLACK, noBorder, true, false, false);

        ConfigureComponent(negative, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(zero, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(decimal, dim, font2, color, Color.BLACK, noBorder, true, false, false);
        ConfigureComponent(equals, dim, font2, color, Color.BLACK, noBorder, true, false, false);

        middlePanel.setBorder(BorderFactory.createMatteBorder(0, 0, 1, 0, color));

    }

    private void ConfigureComponent(JButton component, Dimension size, Font font, Color backgroundColor, Color foreGroundColor, Border border, boolean contentAreaFilled, boolean borderPainted, boolean focusPainted) {
        component.setPreferredSize(size);
        component.setFont(font);
        component.setOpaque(true);
        component.setBackground(backgroundColor);
        component.setForeground(foreGroundColor);
        component.setBorder(border);
        component.setContentAreaFilled(contentAreaFilled);
        component.setBorderPainted(borderPainted);
        component.setFocusPainted(focusPainted);
    }
}

I tried looking for JPanel.setMargin or JPanel.setInsets and couldn't find anything. Not sure on where to look next.

Red border is around my JTextfield, inside of topPanel. Green border is around topPanel. Blue border is around mainPanel. I want to get rid of the space between the green and blue borders. I originally had the borders set to an empty border, I'm just using this for testing my program.

Edit: I just tried topPanel.setLocation(0, 0); but it didn't do anything.

Edit2: I just changed the mainPanel to be a BorderLayout instead of GridBagLayout, and aligned the topPanel to PAGE_START, middlePanel to CENTER and bottomPanel to PAGE_END, which got rid of the space between green and blue border. But now I have a gap between the red and green.

Answer 1

It may not seem like it, but resizability can affect a Window's preferred size, due to a change in window decorations. Call frame.setResizable before calling frame.pack() .