无法在 jpanel 中对齐 jlabel

Question

我在对齐 JLabel 播放按钮时遇到问题。我不知道面板中的其他元素是否会导致问题，但我没有尝试解决此问题。标签显示在屏幕底部（水平居中，因为 setAlignmentX），没有任何东西可以将其向上移动。我所有的组件都位于一条垂直线上，所以我需要使用 BoxLayout。但是，我不明白为什么突然标签的位置离其他元素如此之远，而其他元素看起来完全没问题。

import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Vector;

public class Frame {

private final int WIDTH = 1024;
private final int HEIGHT = 768;
private JFrame frame;
private JPanel panel;
private JLabel human;
private JTextArea text;

public Frame()
{
    this.frame = new JFrame();
    this.panel = new JPanel();
    this.human = ImageSize(200, 200, "res/human.png");
    this.text = new JTextArea("You have lost in the forest. Now you have to find " +
                           "your way back.");

    //frame setup
    frame.setTitle("Shady Path");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLayout(new BorderLayout());
    frame.pack();
    frame.setSize(WIDTH, HEIGHT);
    frame.setLocationRelativeTo(null);
    frame.getContentPane().setBackground(Color.BLACK);
    frame.setResizable(false);

    //main text setup
    Font font = new Font(Font.MONOSPACED, Font.PLAIN, 20);
    text.setEditable(false);
    text.setForeground(Color.WHITE);
    text.setFont(font);
    text.setLineWrap(true);
    text.setWrapStyleWord(true);
    text.setMargin(new Insets(0, 300, 0, 300));
    text.setOpaque(false);

    //button setup
    JButton button = new JButton();
    JLabel playButton = new JLabel("Play");
    playButton.setFont(font);
    playButton.setForeground(Color.WHITE);
    playButton.add(button);

    //panel setup and adding elements
    panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
    panel.setOpaque(false);
    panel.add(Box.createVerticalStrut(50));
    panel.add(human);
    human.setAlignmentX(Component.CENTER_ALIGNMENT);
    panel.add(Box.createVerticalStrut(30));
    panel.add(text);
    text.setAlignmentX(Component.CENTER_ALIGNMENT);
    panel.add(Box.createVerticalStrut(30));
    panel.add(playButton);
    playButton.setAlignmentX(Component.CENTER_ALIGNMENT);
    playButton.setAlignmentY(Component.CENTER_ALIGNMENT);

    frame.add(panel);
    frame.setVisible(true);
}

private JLabel ImageSize(int x, int y, String fileName) //Method for image resizing
{
    BufferedImage baseImg = null;
    try {
        baseImg = ImageIO.read(new File(fileName));
    } catch (IOException e) {
        e.printStackTrace();
    }
    Image resizedImg = baseImg.getScaledInstance(x, y, Image.SCALE_SMOOTH);
    ImageIcon IconImg = new ImageIcon(resizedImg);
    JLabel imageLabel = new JLabel(IconImg);
    return imageLabel;
}

} output of the program

Answer 1

就我个人而言，我会使用GridBagLayout，它更复杂，但更灵活...

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Frame {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                Frame frame = new Frame();
            }
        });
    }

    private final int WIDTH = 1024;
    private final int HEIGHT = 768;
    private JFrame frame;
    private JPanel panel;
    private JLabel human;
    private JTextArea text;

    public Frame() {
        this.frame = new JFrame();
        this.panel = new JPanel();
        this.human = ImageSize(200, 200, "res/human.png");
        this.text = new JTextArea("You have lost in the forest. Now you have to find "
                        + "your way back.");

        //frame setup
        frame.setTitle("Shady Path");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // That's pointless
        //frame.setLayout(new BorderLayout());
        // That's pointless
        //frame.pack();
        frame.setSize(WIDTH, HEIGHT);
        frame.setLocationRelativeTo(null);
        frame.getContentPane().setBackground(Color.BLACK);
        frame.setResizable(false);

        //main text setup
        Font font = new Font(Font.MONOSPACED, Font.PLAIN, 20);
        text.setEditable(false);
        text.setForeground(Color.WHITE);
        text.setFont(font);
        text.setLineWrap(true);
        text.setWrapStyleWord(true);
        text.setMargin(new Insets(0, 300, 0, 300));
        text.setOpaque(false);

        //button setup
        JButton button = new JButton();
        JLabel playButton = new JLabel("Play");
        playButton.setFont(font);
        playButton.setForeground(Color.WHITE);
        playButton.add(button);

        //panel setup and adding elements
        panel.setLayout(new GridBagLayout());
        panel.setOpaque(false);
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.anchor = GridBagConstraints.CENTER;
        gbc.weightx = 1.0;
        gbc.insets = new Insets(50, 0, 0, 0);
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        panel.add(human, gbc);

        gbc.insets = new Insets(30, 0, 0, 0);
        gbc.fill = GridBagConstraints.HORIZONTAL;
        panel.add(text, gbc);

        gbc.fill = GridBagConstraints.NONE;
        panel.add(playButton, gbc);

        frame.add(panel);
        frame.setVisible(true);
    }

    private JLabel ImageSize(int x, int y, String fileName) //Method for image resizing
    {
        BufferedImage baseImg = new BufferedImage(x, y, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = baseImg.createGraphics();
        g2d.setColor(Color.RED);
        g2d.fillRect(0, 0, x, y);
        g2d.dispose();
//      try {
//          baseImg = ImageIO.read(new File(fileName));
//      } catch (IOException e) {
//          e.printStackTrace();
//      }
//      Image resizedImg = baseImg.getScaledInstance(x, y, Image.SCALE_SMOOTH);
//      ImageIcon IconImg = new ImageIcon(resizedImg);
        JLabel imageLabel = new JLabel(new ImageIcon(baseImg));
        return imageLabel;
    }
}

您可能想花更多时间查看Lesson: Laying Out Components Within a Container