private static final char[] HEX_CHAR = {   '0', '1', '2', '3', '4', '5', '6', '7',   '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' }; /** 獲取簽名的MD5摘要 */ public String[] signatureDigest() {   pkgInfo = mContext.getPackageManager().getPackageInfo(         mContext.getPackageName(), PackageManager.GET_SIGNATURES);   int length = pkgInfo.signatures.length;   String[] digests = new String[length];   for (int i = 0; i < length; ++i) {     Signature sign = mPkgInfo.signatures[i];     try {       MessageDigest md5 = MessageDigest.getInstance("MD5");       byte[] digest = md5.digest(sign.toByteArray()); // get digest with md5 algorithm       digests[i] = toHexString(digest);     } catch (NoSuchAlgorithmException e) {       e.printStackTrace();       digests[i] = null;     }   }   return digests; } /** 將字節數組轉化為對應的十六進制字符串 */ private String toHexString(byte[] rawByteArray) {   char[] chars = new char[rawByteArray.length * 2];   for (int i = 0; i < rawByteArray.length; ++i) {     byte b = rawByteArray[i];     chars[i*2] = HEX_CHAR[(b >>> 4 & 0x0F)];     chars[i*2+1] = HEX_CHAR[(b & 0x0F)];   }   return new String(chars); }