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

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;  }    public String getIdentifyCode(){    if(stringBuffer == null){      return "";    }    return stringBuffer.toString();  }    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();  }    private void drawCodeText(Canvas canvas,int width, int height){    Paint paint = new Paint();    paint.setTextSize(50);        String text = buildIdentifyCode();    float textLength = paint.measureText(text);    int startMaxLength = (int) ((width - textLength) / 2);        int startPosition = random.nextInt(startMaxLength);    //绘制文字    for(int index = 0; index < text.length(); index++){            int offsetDegree = random.nextInt(15);            offsetDegree = random.nextInt(2) == 1 ? offsetDegree : -offsetDegree;      canvas.save();      //设置旋转      canvas.rotate(offsetDegree, width / 2, height / 2);            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();    }  }    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);    }  }    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);    }  }}