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Java Swing - 如何创建透明JScrollPane

jscrollpane 【jscrollpane】
我们想知道如何创建透明JScrollPane。
代码展示 运行结果 
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JViewport;

public class Main extends JFrame {
  public Main() {
    JViewport viewport = new MyViewport();
    viewport.setView(new MyPanel());
    JScrollPane scrollPane = new JScrollPane();
    scrollPane.setViewport(viewport);
    add(scrollPane);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    pack();
    setVisible(true);
  }
  public static void main(String[] args) {
    new Main();
  }
}
class MyViewport extends JViewport {
  int TILE = 64;
  public MyViewport() {
    setOpaque(false);
    setPreferredSize(new Dimension(6 * TILE, 6 * TILE));
  }

  @Override
  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(Color.blue);
    g.fillRect(TILE, TILE, 3 * TILE, 3 * TILE);
  }
}
class MyPanel extends JPanel {
  int TILE = 64;
  public MyPanel() {
    setOpaque(false);
    setPreferredSize(new Dimension(9 * TILE, 9 * TILE));
  }
  @Override
  protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(Color.lightGray);
    int w = getWidth() / TILE + 1;
    int h = getHeight() / TILE + 1;
    for (int row = 0; row < h; row++) {
      for (int col = 0; col < w; col++) {
        if ((row + col) % 2 == 0) {
          g.fillRect(col * TILE, row * TILE, TILE, TILE);
        }
      }
    }
  }
}