Question

I tried the following example for applying a linear gradient: GradientPaintDemo2D.

It works well, but I wanted the gradient color to be applied into Java Swing matte border. I tried this:

javax.swing.BorderFactory.createMatteBorder(1, 50, 1, 50, color)

But that’s only for applying one type of Color, not GradientPaint.

As we all know, GradientPaint contains two colors mixed altogether, as shown in the example linked above. So what’s the alternative answer for this case?

Answer 1

How about using new MatteBorder(int, int, int, int, javax.swing.Icon)

//Another example:
import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;

public class GradientMatteBorderTest {
  public JComponent makeUI() {
    Icon icon = new Icon() {
      @Override public void paintIcon(Component c, Graphics g, int x, int y) {
        Graphics2D g2  = (Graphics2D)g.create();
        Point2D start  = new Point2D.Float(0f, 0f);
        Point2D end    = new Point2D.Float(99f, 0f);
        float[] dist   = {0.0f, 0.5f, 1.0f};
        Color[] colors = { Color.RED, Color.YELLOW, Color.GREEN };
        g2.setPaint(new LinearGradientPaint(start, end, dist, colors));
        g2.fillRect(x, y, 100, 10);
        g2.dispose();
      }
      @Override public int getIconWidth()  { return 100; }
      @Override public int getIconHeight() { return 10;  }
    };
    JLabel label = new JLabel("GradientMatteBorder");
    label.setBorder(BorderFactory.createMatteBorder(10,5,10,0,icon));
    JPanel p = new JPanel(new BorderLayout());
    p.setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
    p.add(label, BorderLayout.NORTH);
    return p;
  }
  public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
      @Override public void run() {
        createAndShowGUI();
      }
    });
  }
  public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new GradientMatteBorderTest().makeUI());
    f.setSize(320, 240);
    f.setLocationRelativeTo(null);
    f.setVisible(true);
  }
}