对齐BoxLayout中的JLabels

Question

我已经四处寻找了好几天，试图找到这个问题的答案，但我找不出问题所在。我想做的是使顶部的JLabel（称为display）向右对齐，底部的JLabel2（称为notice）向左对齐。两人似乎都不想这样做。从我所读到的来看，我所拥有的应该有效，但事实并非如此。帮助

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

为了清晰起见，我删除了ActionListener的所有内容。但这是我无法修复的布局。

Answer 1

考虑让topLabel不使用默认的FlowLayout，而是使用一些使其内容填充的东西，如BorderLayout。

topLabel.setLayout(new BorderLayout());

接下来，确保您设置了显示器的水平对齐，而不是其右侧的对齐X：

display.setHorizontalAlignment(SwingConstants.RIGHT);

您的通知JLabel及其容器也应该进行类似的更改。

Answer 2

我添加了几行代码，因为我喜欢BoxLayout。几个小时前，我在对齐组件时遇到了几乎相同的问题。

如果我们想获得这样的

//  +----------------------------------+
//  |  Label1  |            |  Label2  |
//  +----------------------------------+

您只需要在两者之间放置一个"Box.createHorizontalGlue（）"。

如果我们想要这样的东西：

//  +----------------------------------+
//  |  Label1  |                       |
//  |----------+            +----------|
//  |                       |  Label2  |
//  +----------------------------------+

我们必须将标签放在两个不同的JPanel中，为它们设置不同的AlignmentX。这是因为在布局中，所有组件都应该具有相同的对齐X。为了避免这种限制，我们可以这样做：

//  +-----------------------------------------+
//  |  Label1  |   label1 is inside a JPanel  |
//  +----------+ - - - - - - - - - - - - - - -+
//  + - - - - - - - - - - - - - - -+----------+
//  |  label2 also                 |  Label2  |
//  +-----------------------------------------+

（不介意两个面板之间的空间，仅用于图形）这可以用以下代码完成：

mainPanel = new JPanel();
mainPanel.setLayout(new BoxLayout(mainPanel,BoxLayout.PAGE_AXIS));
JLabel lbl1 = new JLabel("Label1");
JPanel p1 = new JPanel();
p1.setOpaque(false);
p1.setLayout(new BorderLayout(0, 0));
p1.add(lbl1, BorderLayout.CENTER);
JLabel lbl2 = new JLabel("Label1");
JPanel p2 = new JPanel();
p2.setOpaque(false);
p2.setLayout(new BorderLayout(0, 0));
p2.add(lbl2, BorderLayout.CENTER);
mainPanel.add(p1);
mainPanel.add(p2);

我希望这是有用的。

Answer 3

您可以简单地使用BorderLayout():

public static void goGUI() {
        ....
        topLabel = new JPanel(new BorderLayout());
        bottomLabel = new JPanel(new BorderLayout());
        ....
        topLabel.add(display, BorderLayout.EAST);
        bottomLabel.add(notice, BorderLayout.WEST);

    }

同时删除这些调用：

 display.setAlignmentX(Component.RIGHT_ALIGNMENT);
 notice.setAlignmentX(Component.LEFT_ALIGNMENT);