java - 在 BoxLayout 中对齐 JLabel

Question

我这几天一直在寻找这个问题的答案，但我找不到问题所在。我想要做的是使顶部 JLabel(称为 display)向右对齐，底部 JLabel(称为 notice)向左对齐。似乎两者都不想这样做。从我读过的内容来看，我所拥有的应该可以工作，但事实并非如此。帮忙？

import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.Border;

public class Calculator {

    private static JButton clear, add, subtract, multiply, divide, equals, point, zero, one, two, three, four, five, six, seven, eight, nine;
    private static JLabel display, notice, blank1, blank2, blank3;
    private static JPanel mainPanel, buttonPanel, topLabel, bottomLabel;

    public static void goGUI() {

        JFrame frame = new JFrame("Calculator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setPreferredSize(new Dimension(600,300));
        mainPanel = new JPanel();
        mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS));
        frame.setContentPane(mainPanel);
        Border empty = BorderFactory.createEmptyBorder(10,10,10,10);
        mainPanel.setBorder(empty);

        buttonPanel = new JPanel(new GridLayout(5,4, 5,5));
        Border buttonBorder = BorderFactory.createEmptyBorder(10,0,10,0);
        buttonPanel.setBorder(buttonBorder);

        topLabel = new JPanel();
        bottomLabel = new JPanel();

        clear = new JButton("C");
        add = new JButton("+");
        subtract = new JButton("-");
        multiply = new JButton("*");
        divide = new JButton("/");
        equals = new JButton("=");
        point = 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");

        // Here I added ActionListeners to all the buttons...

        display = new JLabel("0");
        display.setAlignmentX(Component.RIGHT_ALIGNMENT);
        notice = new JLabel("*Maximum 19 digits - Order of operations not taken into account*");
        notice.setAlignmentX(Component.LEFT_ALIGNMENT);
        blank1 = new JLabel();
        blank2 = new JLabel();
        blank3 = new JLabel();

        buttonPanel.add(clear);
        buttonPanel.add(blank1);
        buttonPanel.add(blank2);
        buttonPanel.add(blank3);
        buttonPanel.add(seven);
        buttonPanel.add(eight);
        buttonPanel.add(nine);
        buttonPanel.add(divide);
        buttonPanel.add(four);
        buttonPanel.add(five);
        buttonPanel.add(six);
        buttonPanel.add(multiply);
        buttonPanel.add(one);
        buttonPanel.add(two);
        buttonPanel.add(three);
        buttonPanel.add(subtract);
        buttonPanel.add(zero);
        buttonPanel.add(point);
        buttonPanel.add(equals);
        buttonPanel.add(add);

        topLabel.add(display);
        bottomLabel.add(notice);

        mainPanel.add(topLabel);
        mainPanel.add(buttonPanel);
        mainPanel.add(bottomLabel);

        frame.pack();
        frame.setVisible(true);

    } //end goGUI

    //ActionListener classes went here...

    public static void main(String[] args) {

        try {
            // Set cross-platform Java L&F (also called "Metal")
            UIManager.setLookAndFeel(
                UIManager.getCrossPlatformLookAndFeelClassName());
        } 
        catch (Exception e) {}

        goGUI();

    } //end main
} //end Calculator

为了清楚起见，我删除了所有 ActionListener 的东西。但这是我无法修复的布局。

Answer 1

考虑让 topLabel 不使用默认的 FlowLayout，而是使用使其内容填满它的东西，例如 BorderLayout。

topLabel.setLayout(new BorderLayout());

接下来确保设置显示器的水平对齐方式，而不是右对齐:

display.setHorizontalAlignment(SwingConstants.RIGHT);

应为您的通知 JLabel 及其容器进行类似的更改。