集成facebooksdk之后，在应用内调用
try {
PackageInfo info = getPackageManager().getPackageInfo(
"com.zy",
PackageManager.GET_SIGNATURES);
for (Signature signature : info.signatures) {
MessageDigest md = MessageDigest.getInstance("SHA");
md.update(signature.toByteArray());
Log.d("KeyHash:", Base64.encodeToString(md.digest(), Base64.DEFAULT));
}
} catch (PackageManager.NameNotFoundException e) {
} catch (NoSuchAlgorithmException e) {
}
