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);  } }