swing构建不规则窗体

Java从JDK 6 update 10开始将内建支持构建指定形状的窗体，类com.sun.awt.AWTUtilities中的方法setWindowShape会根据不同的Shape实现去构造相应形状的窗体。AWTUtilities类是放在SUN的包中，在使用该方法时应该通过反射去进行调用，如下代码所示，
Class<?> clazz = Class.forName("com.sun.awt.AWTUtilities");
Method method = clazz.getMethod("setWindowShape", Window.class, Shape.class);

1. 创建正常窗体
先创建一个简单的界面，它使用BorderLayout，在其中安放5个JButton，如下代码所示

import java.awt.*;
import javax.swing.*;
public class ShapedFrame extends JFrame {
    private static final long serialVersionUID = -2291343874280454383L;
    private JButton centerButton = new JButton(Center);
    public ShapedFrame() {
        super(Shaped Frame);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        initUI();
    }
    private void initUI() {
        Container container = getContentPane();
        container.setLayout(new BorderLayout());
        container.add(new JButton(TOP), BorderLayout.PAGE_START);
        container.add(new JButton(RIGHT), BorderLayout.LINE_END);
        container.add(new JButton(BOTTOM), BorderLayout.PAGE_END);
        container.add(new JButton(LEFT), BorderLayout.LINE_START);
        container.add(centerButton, BorderLayout.CENTER);
    }
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                ShapedFrame frame = new ShapedFrame();
                frame.setSize(new Dimension(400, 300));
                frame.setUndecorated(true);
                setAtCenter(frame);
                frame.setVisible(true);
            }
        });
    }
    // 将Window置于屏幕正中
    private static void setAtCenter(Window window) {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        window.setLocation((screenSize.width - window.getWidth()) / 2,
                (screenSize.height - window.getHeight()) / 2);
    }
}

效果图：

2. 创建不规则窗体
基于上述程序创建不规则窗体，使整个窗体正好缺失掉RIGHT JButton所在的区域，如下代码所示

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.reflect.Method;
public class ShapedFrame extends JFrame {
    private static final long serialVersionUID = -2291343874280454383L;
    private static Method method = null;
    static {
        try {
            Class< ?> clazz = Class.forName(com.sun.awt.AWTUtilities);
            method = clazz.getMethod(setWindowShape, Window.class, Shape.class);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private JButton centerButton = new JButton(Center);
    public ShapedFrame() {
        super(Shaped Frame);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        initUI();
        addComponentListener(componentListener);
    }
    private void initUI() {
        Container container = getContentPane();
        container.setLayout(new BorderLayout());
        container.add(new JButton(TOP), BorderLayout.PAGE_START);
        container.add(new JButton(RIGHT), BorderLayout.LINE_END);
        container.add(new JButton(BOTTOM), BorderLayout.PAGE_END);
        container.add(new JButton(LEFT), BorderLayout.LINE_START);
        container.add(centerButton, BorderLayout.CENTER);
    }
    private ComponentListener componentListener = new ComponentAdapter() {
        @Override
        public void componentResized(ComponentEvent evt) { // 当UI组件(JFrame)的尺寸发生改变时，调用该方法
            Rectangle frameRect = getBounds();
            Rectangle spaceRect = centerButton.getBounds();
            Point o1 = new Point(0, 0);
            Point o2 = new Point(frameRect.width, 0);
            Point o3 = new Point(frameRect.width, frameRect.height);
            Point o4 = new Point(0, frameRect.height);
            Point i1 = new Point(spaceRect.x + spaceRect.width, spaceRect.y);
            Point i2 = new Point(frameRect.width, spaceRect.y);
            Point i3 = new Point(frameRect.width, spaceRect.y
                    + spaceRect.height);
            Point i4 = new Point(spaceRect.x + spaceRect.width, spaceRect.y + spaceRect.height);
            int[] xpoints = new int[] { o1.x, o2.x, i2.x, i1.x, i4.x, i3.x, o3.x, o4.x };
            int[] ypoints = new int[] { o1.y, o2.y, i2.y, i1.y, i4.y, i3.y, o3.y, o4.y };
            int npoints = 8;
            // 构建一个六边形，将RIGHT JButton所处的位置空缺出来
            Shape shape = new Polygon(xpoints, ypoints, npoints);
            setWindowShape(ShapedFrame.this, shape);
        }
    };
    // 设置Window的形状
    private static void setWindowShape(Window window, Shape shape) {
        try {
            method.invoke(null, window, shape);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                ShapedFrame frame = new ShapedFrame();
                frame.setSize(new Dimension(400, 300));
                frame.setUndecorated(true);
                setAtCenter(frame);
                frame.setVisible(true);
            }
        });
    }
    // 将Window置于屏幕正中
    private static void setAtCenter(Window window) {
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        window.setLocation((screenSize.width - window.getWidth()) / 2,
                (screenSize.height - window.getHeight()) / 2);
    }
}

效果图：