import java.util.Random;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
 
public class Autjcode {
    private static Autjcode bmpCode;
    private int width = 100, height = 60;
    private int base_padding_left = 15, range_padding_left = 5,
            base_padding_top = 25, range_padding_top = 30;
    private int codeLength = 4, line_number = 2, font_size = 25;
    private String code;
    private int padding_left, padding_top;
    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' };
 
    /**
     * 获得实例
     * 
     * @return
     */
    public static Autjcode getInstance() {
        if (bmpCode == null)
            bmpCode = new Autjcode();
        return bmpCode;
    }
 
    private Random random = new Random();
 
    /**
     * 创建位图
     * 
     * @return
     */
    public Bitmap createBitmap() {
        padding_left = 0;
        // ARGB_8888表示为32位的ARGB位图
        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);
        paint.setFakeBoldText(true);
 
        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();
    }
 
    /**
     * 划线
     * 
     * @param canvas
     * @param paint
     */
    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());
        float skewX = random.nextInt(11) / 10;
        skewX = random.nextBoolean() ? skewX : -skewX;
        paint.setTextSkewX(skewX);
    }
 
    private void randomPadding() {
        padding_left += base_padding_left + random.nextInt(range_padding_left);
        padding_top = base_padding_top + random.nextInt(range_padding_top);
    }
}

使用方法：
初始化：

registerAuthimg = (ImageView) findViewById(R.id.registerAuthimg);
registerAuthimg.setImageBitmap(Autjcode.getInstance().createBitmap());

验证码刷新：

registerAuthimg.setImageBitmap(Autjcode.getInstance().createBitmap());

获取当前显示的文字验证码：

String Autecodeimg = Autjcode.getInstance().getCode().toUpperCase();

来源与个人博客：http://www.coocj.top/post-41.html