android通过代码获得sha1的值

public String sHA1() {    try {        PackageInfo info = getPackageManager().getPackageInfo(getPackageName(), PackageManager.GET_SIGNATURES);        byte[] cert = info.signatures[0].toByteArray();        MessageDigest md = MessageDigest.getInstance("SHA1");        byte[] publicKey = md.digest(cert);        StringBuffer hexString = new StringBuffer();        for (int i = 0; i < publicKey.length; i++) {            String appendString = Integer.toHexString(0xFF & publicKey[i])                    .toUpperCase(Locale.US);            if (appendString.length() == 1)                hexString.append("0");            hexString.append(appendString);            hexString.append(":");        }        String result = hexString.toString();        return result.substring(0, result.length()-1);    } catch (PackageManager.NameNotFoundException e) {        e.printStackTrace();    } catch (NoSuchAlgorithmException e) {        e.printStackTrace();    }    return null;}