swing重绘按钮为任意形状图案的方法

import javax.imageio.ImageIO; 
import javax.swing.*; 
import java.awt.*; 
import java.awt.image.BufferedImage; 
 
public class newButton extends JButton{ 
 ImageIcon img; 
 public newButton(String icon){ 
  super(); 
  this.img = new ImageIcon(Demo.class.getResource(icon)); 
  setBorderPainted(false); 
  setContentAreaFilled(false); 
  setOpaque(false); 
  setSize(img.getIconWidth(),img.getIconHeight()); 
  try{ 
   bi = ImageIO.read(Demo.class.getResource(icon)); 
  }catch(Exception e){ 
   JOptionPane.showMessageDialog(this,"可能是图片文件不存在","ImageIO异常",JOptionPane.ERROR_MESSAGE); 
   System.exit(0); 
  } 
 } 
 @Override 
 public void paintComponent(Graphics g){ 
  if(this.getModel().isPressed()){ 
   g.drawImage(img.getImage(),1,1,this); 
  }else{ 
   g.drawImage(img.getImage(),0,0,this); 
  } 
  super.paintComponent(g); 
 } 
 BufferedImage bi ; 
 int rgb,alpha; 
 /** 
  * 设置按钮点击范围仅在图片的非透明区域。 
  */ 
 @Override 
 public boolean contains(int x,int y){ 
  try{ 
   rgb = bi.getRGB(x,y); 
   alpha = (rgb>>24)&0xFF; 
   if(alpha==0){ 
    return false; 
   }else{ 
    return true; 
   } 
  }catch(ArrayIndexOutOfBoundsException e){ 
   //当搜索到透明区域时，就getRGB抛出下表越界异常 
   return false; 
  } 
 } 
} 

import javax.swing.*; 
import java.awt.*; 
import java.net.URL; 
 
public class Demo { 
 public Demo(){ 
  JFrame jf=new JFrame("任意形状图片按钮测试"); 
  jf.setBounds(500,200,700,500); 
 
  myJPanel jp = new myJPanel(Demo.class.getResource("bg.jpg")); 
  jp.setLayout(null); 
 
  newButton jb1 = new newButton("bt1.png"); 
  jb1.setLocation(44,44); 
  jp.add(jb1); 
 
  jb1 = new newButton("snowFlower.png"); 
  jb1.setLocation(200,44); 
  jp.add(jb1); 
 
  jb1 = new newButton("bt2.png"); 
  jb1.setLocation(350,64); 
  jp.add(jb1); 
 
  jb1 = new newButton("bt3.png"); 
  jb1.setLocation(450,64); 
  jp.add(jb1); 
 
  jf.add(jp); 
  jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
  jf.setVisible(true); 
 } 
 public static void main(String[] args){ 
  new Demo(); 
 } 
 private class myJPanel extends JPanel{ 
  ImageIcon bg; 
  public myJPanel(URL bg) { 
   this.setOpaque(false);//要设置为透明。 
   this.bg = new ImageIcon(bg); 
  } 
  //用于设置背景图片 
  @Override 
  public void paintComponent(Graphics g){ 
   g.drawImage(bg.getImage(),0,0,this.getWidth(),this.getHeight(),this); 
   super.paintComponent(g); 
  } 
 } 
}