Android绘制验证码的实例代码

/**
 * Created by Iflytek_dsw on 2017/7/3.
 */
public class IdentifyCodeUtil {
  private static final int CODE_NUMBER = 4;
  private static final int LINE_NUMBER = 5;
  private static final int POINT_NUMBER = 10;
  private StringBuffer stringBuffer = null;
  private Random random = new Random();
  //随机数数组
  private static final char[] CHARS = {
      '2', '3', '4', '5', '6', '7', '8', '9',
      'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', '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 IdentifyCodeUtil instance;
  public static IdentifyCodeUtil getInstance(){
    if(instance == null){
      instance = new IdentifyCodeUtil();
    }
    return instance;
  }
  public Bitmap createBitmapCode(int width, int height){
    Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    canvas.drawColor(Color.LTGRAY);
    drawCodeText(canvas, width, height);
    drawLines(canvas, width, height);
    drawPoint(canvas, width, height);
    return bitmap;
  }
  /**
   * 返回验证码
   * @return 验证码生成的字符串
   */
  public String getIdentifyCode(){
    if(stringBuffer == null){
      return "";
    }
    return stringBuffer.toString();
  }
  /**
   * 生成验证码
   * @return
   */
  private String buildIdentifyCode(){
    StringBuffer stringBuffer = new StringBuffer();
    for(int i=0; i < CODE_NUMBER;i++){
      stringBuffer.append(CHARS[random.nextInt(CHARS.length)]);
    }
    Log.d("Code",stringBuffer.toString());
    return stringBuffer.toString();
  }
  /**
   * 绘制文本
   * @param canvas  画布
   * @param width   宽度
   * @param height  高度
   */
  private void drawCodeText(Canvas canvas,int width, int height){
    Paint paint = new Paint();
    paint.setTextSize(50);
    /**构建验证码code*/
    String text = buildIdentifyCode();
    float textLength = paint.measureText(text);
    int startMaxLength = (int) ((width - textLength) / 2);
    /**随机计算验证码绘制每次开头的位置*/
    int startPosition = random.nextInt(startMaxLength);
    //绘制文字
    for(int index = 0; index < text.length(); index++){
      /**生成旋转的角度*/
      int offsetDegree = random.nextInt(15);
      /**这里只会产生0和1，如果是1那么正旋转正角度，否则旋转负角度*/
      offsetDegree = random.nextInt(2) == 1 ? offsetDegree : -offsetDegree;
      canvas.save();
      //设置旋转
      canvas.rotate(offsetDegree, width / 2, height / 2);
      /**生成随机的颜色*/
      paint.setARGB(255, random.nextInt(200) + 20, random.nextInt(200) + 20,
          random.nextInt(200) + 20);
      char tempChar = text.charAt(index);
      //给画笔设置随机颜色
      canvas.drawText(String.valueOf(tempChar), startPosition +index * textLength / text.length() +15,
          height * 3 / 5f,paint);
      canvas.restore();
    }
  }
  /**
   * 生成干扰线
   * @param canvas
   * @param width
   * @param height
   */
  private void drawLines(Canvas canvas,int width, int height){
    Paint paint = new Paint();
    paint.setStrokeWidth(3);
    for(int i = 0;i < LINE_NUMBER;i++){
      paint.setARGB(255, random.nextInt(200) + 30, random.nextInt(200) + 30, random.nextInt(200) + 30);
      int startX = random.nextInt(width);
      int startY = random.nextInt(height);
      int endX = random.nextInt(width);
      int endY = random.nextInt(height);
      canvas.drawLine(startX, startY, endX, endY, paint);
    }
  }
  /**
   * 生成干扰点
   */
  private void drawPoint(Canvas canvas, int width, int height) {
    Paint paint = new Paint();
    paint.setStrokeWidth(3);
    paint.setColor(Color.GRAY);
    for(int i=0; i< POINT_NUMBER; i++){
      PointF pointF = new PointF(random.nextInt(width) + 10, random.nextInt(height) + 10);
      canvas.drawPoint(pointF.x, pointF.y, paint);
    }
  }
}