如何使用 Java Swing 创建简单的圆角矩形按钮？

Question

我使用一个简单的“计算器”项目作为圆角矩形按钮的示例。整个项目由一个小的类文件组成。这里是：

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.KeyEvent;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JPanel;
import javax.swing.JTextField;

/**
 * Swing layout management tutorial
 *
 * This program shows how to use the
 * GridLayout manager to create a
 * calculator skeleton.
 *
 * @author jan bodnar
 * website zetcode.com
 * last modified February 2009
 */
public class Calculator extends JFrame {

    public Calculator() {
        setTitle("Calculator");
        initUI();
        setSize(320, 290);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    public void initUI() {
        JMenuBar menubar = new JMenuBar();
        JMenu file = new JMenu("File");
        file.setMnemonic(KeyEvent.VK_F);
        menubar.add(file);
        setJMenuBar(menubar);

        String[] labels = {
            "Cls", "Bck", "", "Close",
            "7", "8", "9", "/",
            "4", "5", "6", "*",
            "1", "2", "3", "-",
            "0", ".", "=", "+"
        };
        JTextField field = new JTextField();
        add(field, BorderLayout.NORTH);
        JPanel buttonPanel = new JPanel(new GridLayout(5, 4, 3, 3));
        buttonPanel.setBorder(BorderFactory.createEmptyBorder(8, 0, 0, 0));

        for (String label: labels) {
            if (label.isEmpty()) {
                JLabel lbl = new JLabel();
                buttonPanel.add(lbl);
            } else {
                JButton button = new JButton(label);
                buttonPanel.add(button);
            }
        }
        add(buttonPanel, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        new Calculator();
    }
}

运行时，它会生成带有扁平、略带 3D 外观的漂亮矩形标签按钮。我试图获得如下相同的效果：

    FlowLayout flowLayoutManager = new FlowLayout(FlowLayout.RIGHT);
    JPanel lowerPanel = new JPanel(flowLayoutManager);
    lowerPanel.setBorder(
            BorderFactory.createEtchedBorder(
            EtchedBorder.RAISED));
    lowerPanel.setBackground(Color.ORANGE);
    lowerPanel.setPreferredSize(new Dimension(700, 100));
    lowerPanel.setMaximumSize(lowerPanel.getPreferredSize());
    lowerPanel.setMinimumSize(lowerPanel.getPreferredSize());

    /*
     * cardReaderButtonPanel holds three card reader control buttons
     */
    JPanel cardReaderButtonPanel = new JPanel(new GridLayout(1, 3, 10, 0));
    cardReaderButtonPanel.setBorder(BorderFactory.createEmptyBorder(8, 0, 0, 0));
    cardReaderButtonPanel.setOpaque(false); // transparent background

    String[] labels = {"Load", "Stop", "Start"};
    for (String label : labels) {
        JButton button = new JButton(label);
        cardReaderButtonPanel.add(button);
    }
    lowerPanel.add(cardReaderButtonPanel);

...但是 my 按钮看起来像 Mac OS X Aqua 菱形！与计算器示例不同，我将按钮面板添加到一个封闭面板中，该面板本身由 BorderLayout 的中心包围 - 但我看不出这会如何影响按钮的绘制方式。

Answer 1

在 Mac OS X 上，按钮的外观由 com.apple.laf.AquaButtonUI 的实例提供。当按钮的首选大小在特定范围内时，显示为here；否则显示为here。请注意，这两个程序都使用GridLayout；但前者使用按钮的首选大小，而后者拉伸按钮以填充封闭面板的首选大小。调整框架大小以查看效果。

您的示例使用 FlowLayout，这取决于按钮的首选大小。

附录：BorderLayout 的中心在这方面与GridLayout 的行为相似。尝试为五个BorderLayout 区域中的每一个区域添加一个按钮，然后调整框架大小以查看效果。