android端实现验证码随机生成功能

package com.nobeg.util; 
 
import java.util.Random; 
 
import android.graphics.Bitmap; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Bitmap.Config; 
 
public class Code { 
  
 private static final char[] CHARS = { 
  '2', '3', '4', '5', '6', '7', '8', '9', 
  'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'l', 'm', 
  'n', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 
  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 
  'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' 
 }; 
  
 private static Code bmpCode; 
  
 public static Code getInstance() { 
  if(bmpCode == null) 
   bmpCode = new Code(); 
  return bmpCode; 
 } 
  
 //default settings 
 private static final int DEFAULT_CODE_LENGTH = 3; 
 private static final int DEFAULT_FONT_SIZE = 25; 
 private static final int DEFAULT_LINE_NUMBER = 2; 
 private static final int BASE_PADDING_LEFT = 5, RANGE_PADDING_LEFT = 15, BASE_PADDING_TOP = 15, RANGE_PADDING_TOP = 20; 
 private static final int DEFAULT_WIDTH = 60, DEFAULT_HEIGHT = 40; 
  
 //settings decided by the layout xml 
 //canvas width and height 
 private int width = DEFAULT_WIDTH, height = DEFAULT_HEIGHT; 
  
 //random word space and pading_top 
 private int base_padding_left = BASE_PADDING_LEFT, range_padding_left = RANGE_PADDING_LEFT, 
   base_padding_top = BASE_PADDING_TOP, range_padding_top = RANGE_PADDING_TOP; 
  
 //number of chars, lines; font size 
 private int codeLength = DEFAULT_CODE_LENGTH, line_number = DEFAULT_LINE_NUMBER, font_size = DEFAULT_FONT_SIZE; 
  
 //variables 
 private String code; 
 private int padding_left, padding_top; 
 private Random random = new Random(); 
 //验证码图片 
 public Bitmap createBitmap() { 
  padding_left = 0; 
   
  Bitmap bp = Bitmap.createBitmap(width, height, Config.ARGB_8888); 
  Canvas c = new Canvas(bp); 
 
  code = createCode(); 
   
  c.drawColor(Color.WHITE); 
  Paint paint = new Paint(); 
  paint.setTextSize(font_size); 
   
  for (int i = 0; i < code.length(); i++) { 
   randomTextStyle(paint); 
   randomPadding(); 
   c.drawText(code.charAt(i) + "", padding_left, padding_top, paint); 
  } 
 
  for (int i = 0; i < line_number; i++) { 
   drawLine(c, paint); 
  } 
   
  c.save( Canvas.ALL_SAVE_FLAG );//保存 
  c.restore();// 
  return bp; 
 } 
  
 public String getCode() { 
  return code; 
 } 
  
 //验证码 
 private String createCode() { 
  StringBuilder buffer = new StringBuilder(); 
  for (int i = 0; i < codeLength; i++) { 
   buffer.append(CHARS[random.nextInt(CHARS.length)]); 
  } 
  return buffer.toString(); 
 } 
  
 private void drawLine(Canvas canvas, Paint paint) { 
  int color = randomColor(); 
  int startX = random.nextInt(width); 
  int startY = random.nextInt(height); 
  int stopX = random.nextInt(width); 
  int stopY = random.nextInt(height); 
  paint.setStrokeWidth(1); 
  paint.setColor(color); 
  canvas.drawLine(startX, startY, stopX, stopY, paint); 
 } 
  
 private int randomColor() { 
  return randomColor(1); 
 } 
 
 private int randomColor(int rate) { 
  int red = random.nextInt(256) / rate; 
  int green = random.nextInt(256) / rate; 
  int blue = random.nextInt(256) / rate; 
  return Color.rgb(red, green, blue); 
 } 
  
 private void randomTextStyle(Paint paint) { 
  int color = randomColor(); 
  paint.setColor(color); 
  paint.setFakeBoldText(random.nextBoolean()); //true为粗体，false为非粗体 
  float skewX = random.nextInt(11) / 10; 
  skewX = random.nextBoolean() ? skewX : -skewX; 
  paint.setTextSkewX(skewX); //float类型参数，负数表示右斜，整数左斜 
//  paint.setUnderlineText(true); //true为下划线，false为非下划线 
//  paint.setStrikeThruText(true); //true为删除线，false为非删除线 
 } 
  
 private void randomPadding() { 
  padding_left += base_padding_left + random.nextInt(range_padding_left); 
  padding_top = base_padding_top + random.nextInt(range_padding_top); 
 } 
} 

yanzhengma_img = (ImageView) findViewById(R.id.yanzhengma_img); 
  yanzhengma_huan = (Button) findViewById(R.id.yanzhengma_huan); 
  yanzhengma_val = (EditText) findViewById(R.id.yanzhengma_val); 
 
   yanzhengma_img.setImageBitmap(code.getInstance().createBitmap()); 
   
   System.out.println("验证码："+code.getInstance().getCode()); 
   
   yanzhengma_huan.setOnClickListener(new View.OnClickListener() { 
   
   public void onClick(View v) { 
   
   yanzhengma_img.setImageBitmap(code.getInstance().createBitmap()); 
   System.out.println("验证码："+code.getInstance().getCode()); 
   } 
  });