// Paint the BG color of the parent, everywhere outside the clip// of the text bubble.
请参阅源代码中的这一点，该源正确显示为：
import java.awt.*;import java.awt.image.*;import java.awt.geom.*;import javax.swing.*;import javax.swing.border.*;public class BorderTest { public static void main(String[] args) { Runnable r = new Runnable() { @Override public void run() { JPanel gui = new JPanel(new GridLayout(2,0,5,5)); gui.setBorder(new EmptyBorder(10,10,10,10)); gui.setBackground(Color.RED); AbstractBorder brdrLeft = new TextBubbleBorder(Color.BLACK,2,16,16); AbstractBorder brdrRight = new TextBubbleBorder(Color.BLACK,2,16,16,false); JLabel l1 = new JLabel("Label 1"); l1.setBorder(brdrRight); gui.add(l1); JLabel l2 = new JLabel("Label 2"); l2.setBorder(brdrLeft); l2.setBackground(Color.YELLOW); l2.setOpaque(true); gui.add(l2); JPanel p1 = new JPanel(); p1.add(new JLabel("Panel 1")); p1.setBorder(brdrRight); p1.setOpaque(false); gui.add(p1); JPanel p2 = new JPanel(); p2.add(new JLabel("Panel 2")); p2.setBorder(brdrLeft); gui.add(p2); JOptionPane.showMessageDialog(null, gui); } }; // Swing GUIs should be created and updated on the EDT // http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html SwingUtilities.invokeLater(r); }}class TextBubbleBorder extends AbstractBorder { private Color color; private int thickness = 4; private int radii = 8; private int pointerSize = 7; private Insets insets = null; private BasicStroke stroke = null; private int strokePad; private int pointerPad = 4; private boolean left = true; RenderingHints hints; TextBubbleBorder( Color color) { this(color, 4, 8, 7); } TextBubbleBorder( Color color, int thickness, int radii, int pointerSize) { this.thickness = thickness; this.radii = radii; this.pointerSize = pointerSize; this.color = color; stroke = new BasicStroke(thickness); strokePad = thickness / 2; hints = new RenderingHints( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); int pad = radii + strokePad; int bottomPad = pad + pointerSize + strokePad; insets = new Insets(pad, pad, bottomPad, pad); } TextBubbleBorder( Color color, int thickness, int radii, int pointerSize, boolean left) { this(color, thickness, radii, pointerSize); this.left = left; } @Override public Insets getBorderInsets(Component c) { return insets; } @Override public Insets getBorderInsets(Component c, Insets insets) { return getBorderInsets(c); } @Override public void paintBorder( Component c, Graphics g, int x, int y, int width, int height) { Graphics2D g2 = (Graphics2D) g; int bottomLineY = height - thickness - pointerSize; RoundRectangle2D.Double bubble = new RoundRectangle2D.Double( 0 + strokePad, 0 + strokePad, width - thickness, bottomLineY, radii, radii); Polygon pointer = new Polygon(); if (left) { // left point pointer.addPoint( strokePad + radii + pointerPad, bottomLineY); // right point pointer.addPoint( strokePad + radii + pointerPad + pointerSize, bottomLineY); // bottom point pointer.addPoint( strokePad + radii + pointerPad + (pointerSize / 2), height - strokePad); } else { // left point pointer.addPoint( width - (strokePad + radii + pointerPad), bottomLineY); // right point pointer.addPoint( width - (strokePad + radii + pointerPad + pointerSize), bottomLineY); // bottom point pointer.addPoint( width - (strokePad + radii + pointerPad + (pointerSize / 2)), height - strokePad); } Area area = new Area(bubble); area.add(new Area(pointer)); g2.setRenderingHints(hints); // Paint the BG color of the parent, everywhere outside the clip // of the text bubble. Component parent = c.getParent(); if (parent!=null) { Color bg = parent.getBackground(); Rectangle rect = new Rectangle(0,0,width, height); Area borderRegion = new Area(rect); borderRegion.subtract(area); g2.setClip(borderRegion); g2.setColor(bg); g2.fillRect(0, 0, width, height); g2.setClip(null); } g2.setColor(color); g2.setStroke(stroke); g2.draw(area); }}
