Android绘制验证码的实例代码

在前面仿华为加载动画、仿网易音乐听歌识曲-麦克风动画中，我们通过绘图的基础知识完成了简单的绘制。在本例中，我们将绘制常见的验证码。

一、效果图

二、知识点与思路分析

通过上面的效果图观察，我们可以看到里面有绘制的随机线条，随机绘制的验证码。

绘制线条，直线或曲线

绘制文本，生成的验证码文本的绘制

绘制圆点。

三、代码编写

/**
 * 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);
    }
  }
}

以上所述是小编给大家介绍的android绘制验证码的实例代码，希望对大家有所帮助