Android生成验证码Bitmap，主要使用Canvas绘制，实现的步骤如下：
1.生成验证码。主要采用java的随机函数生成序号，然后对应获取预设的Char数组的值，生成长度固定的验证码；
2.Canvas绘制验证码，生成Bitmap.
关键实现代码如下：
1）验证码Char数组
private static final char[] CHARS = { ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘, ‘h‘, ‘i‘, ‘j‘, ‘k‘, ‘l‘, ‘m‘, ‘n‘, ‘o‘, ‘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‘, ‘O‘, ‘P‘, ‘Q‘, ‘R‘, ‘S‘, ‘T‘, ‘U‘, ‘V‘, ‘W‘, ‘X‘, ‘Y‘, ‘Z‘ };
2）生成验证码
public String createCode() { StringBuffer buffer = new StringBuffer(); for (int i = 0; i < codeLength; i++) {//codeLength为生成的验证码的长度 buffer.append(CHARS[random.nextInt(CHARS.length)]);//random为Random变量 } return buffer.toString(); }
3）生成Bitmap
public Bitmap createCodeBitmap() { padding_left = 0; base_padding_left = width / codeLength; Bitmap bitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888); Canvas canvas = new Canvas(bitmap); code = createCode(); canvas.drawColor(Color.WHITE); Paint paint = new Paint(); paint.setTextSize(fontSize); paint.setColor(Color.BLUE); for (int i = 0; i < code.length(); i++) { randomTextStyle(paint); randomPadding(i); canvas.drawText(String.valueOf(code.charAt(i)), padding_left, base_padding_top + range_padding_top, paint); } for (int i = 0; i < lineNumber; i++) { drawLine(canvas, paint);//在生成的bitmap上画线 } for (int i = 0; i < 255; i++) { drawPoints(canvas, paint);//在生成的bitmap上画点 } canvas.save(Canvas.ALL_SAVE_FLAG); canvas.restore(); return bitmap; }
上述三个主要是该功能的主要函数及变量，而在生成验证码bitmap时，最主要的函数是canvas.drawText(String text,Float x,Float y,Paint)，该函数在bitmap的(x,y)点上绘制text的内容。
使用方法如下：
ivVerifyNum = (ImageView) findViewById(R.id.iv_verify_num);
ivVerifyNum.setImageBitmap(SecurityCodeUtil.getInstance()
.createCodeBitmap());
SecurityCodeUtil.java
package com.gx.chezthb.util; 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; /** * * * description: 动态验证码生成<br/> * * author: fanruifa <br/> * * date: 2013-4-16 <br/> * */ public class SecurityCodeUtil { private static final int DEFAULT_CODE_LENGTH = 6; private static final int DEFAULT_FONT_SIZE = 30; private static final int DEFAULT_LINE_NUMBER = 3; private static final int BASE_PADDING_LEFT = 5; private static final int RANGE_PADDING_LEFT = 10; private static final int BASE_PADDING_TOP = 15; private static final int RANGE_PADDING_TOP = 10; private static final int DEFAULT_WIDTH = 140; private static final int DEFAULT_HEIGHT = 39; private static final char[] CHARS = { ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘, ‘h‘, ‘i‘, ‘j‘, ‘k‘, ‘l‘, ‘m‘, ‘n‘, ‘o‘, ‘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‘, ‘O‘, ‘P‘, ‘Q‘, ‘R‘, ‘S‘, ‘T‘, ‘U‘, ‘V‘, ‘W‘, ‘X‘, ‘Y‘, ‘Z‘ }; private static SecurityCodeUtil securityCodeUtil = null; private int width = DEFAULT_WIDTH; private int height = DEFAULT_HEIGHT; private int base_padding_left = BASE_PADDING_LEFT; private int base_padding_top = BASE_PADDING_TOP; private int range_padding_left = RANGE_PADDING_LEFT; private int range_padding_top = RANGE_PADDING_TOP; private int codeLength = DEFAULT_CODE_LENGTH; private int lineNumber = DEFAULT_LINE_NUMBER; private int fontSize = DEFAULT_FONT_SIZE; private String code; private int padding_left, padding_top; private Random random = new Random(); private SecurityCodeUtil() { } public static SecurityCodeUtil getInstance() { if (securityCodeUtil == null) { securityCodeUtil = new SecurityCodeUtil(); } return securityCodeUtil; } public String createCode() { StringBuffer buffer = new StringBuffer(); for (int i = 0; i < codeLength; i++) { buffer.append(CHARS[random.nextInt(CHARS.length)]); } return buffer.toString(); } public Bitmap createCodeBitmap() { padding_left = 0; base_padding_left = width / codeLength; Bitmap bitmap = Bitmap.createBitmap(width, height, Config.ARGB_8888); Canvas canvas = new Canvas(bitmap); code = createCode(); canvas.drawColor(Color.WHITE); Paint paint = new Paint(); paint.setTextSize(fontSize); paint.setColor(Color.BLUE); for (int i = 0; i < code.length(); i++) { randomTextStyle(paint); randomPadding(i); canvas.drawText(String.valueOf(code.charAt(i)), padding_left, base_padding_top + range_padding_top, paint); } for (int i = 0; i < lineNumber; i++) { drawLine(canvas, paint); } for (int i = 0; i < 255; i++) { drawPoints(canvas, paint); } canvas.save(Canvas.ALL_SAVE_FLAG); canvas.restore(); return bitmap; } public String getCode() { return code; } 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 int randomColor() { return randomColor(1); } 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); } private void randomPadding(int i) { padding_left = base_padding_left * i + random.nextInt(range_padding_left); } 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 void drawPoints(Canvas canvas, Paint paint){ int color = randomColor(); int stopX = random.nextInt(width); int stopY = random.nextInt(height); paint.setStrokeWidth(1); paint.setColor(color); canvas.drawPoint(stopX, stopY, paint); } }