Swing-setOpaque()用法-入门

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;

/*
 * 2015-06-15
 */

public class SetOpaqueDemo extends JFrame {

  public SetOpaqueDemo() {
    super("setOpaqueDemo");
    setSize(400, 200);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    //不透明，看到黑色顶层
    JPanel opaquePanel = createNested(true);
    //透明，露出白色底层
    JPanel notOpaque = createNested(false);

    getContentPane().setLayout(new FlowLayout());
    getContentPane().add(opaquePanel);
    getContentPane().add(notOpaque);
  }

  

  public JPanel createNested(boolean opaque) {
    JPanel outer = new JPanel(new FlowLayout());
    JPanel inner = new JPanel(new FlowLayout());
    //底层panel为白色，顶层为黑色    
    outer.setBackground(Color.white);
    inner.setBackground(Color.black);

    inner.setOpaque(opaque);
    inner.setBorder(BorderFactory.createLineBorder(Color.gray));
    inner.setPreferredSize(new Dimension(40, 20));
    outer.add(inner);

    return outer;
  }
  
  public static void main(String[] args) {
        SetOpaqueDemo setOpaqueDemo = new SetOpaqueDemo();
        setOpaqueDemo.setVisible(true);
      }
}