If you need to integrate Facebook SDK in your android app you have to generate keyhash, to configure Facebook API console. Add this method to your utility class and call this method from onCreate() of any Activity. For digital data integrity and authentication we need Signature class which provide the functionality of digital signature algorithm.

public static String generateKeyHash(Activity context) {
        PackageInfo packageInfo;
        String key = null;
        
	try {
            //getting application package name, as defined in manifest
            String packageName = context.getApplicationContext().getPackageName();

            // Retriving package name
            packageInfo = context.getPackageManager().getPackageInfo(packageName, PackageManager.GET_SIGNATURES);

            Log.e("Package Name=", context.getApplicationContext().getPackageName());

            for (Signature signature : packageInfo.signatures) {
                MessageDigest md = MessageDigest.getInstance("SHA");
                md.update(signature.toByteArray());
                key = new String(Base64.encode(md.digest(), 0));

                // String key = new String(Base64.encodeBytes(md.digest()));
                Log.e("Key Hash=", key);
            }
        } catch (PackageManager.NameNotFoundException e1) {
            Log.e("Name not found", e1.toString());
        }
        catch (NoSuchAlgorithmException e) {
            Log.e("No such an algorithm", e.toString());
        } catch (Exception e) {
            Log.e("Exception", e.toString());
        }

        return key;
    }