private CallbackManager callbackManager;
 private LoginButton btnFBlogin;

@Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FacebookSdk.sdkInitialize(getApplicationContext());
        callbackManager = CallbackManager.Factory.create();

        setContentView(R.layout.activity_login);


        etusername = (EditText) findViewById(R.id.etusername);
        etpassword = (EditText) findViewById(R.id.etpassword);
        btnlogin = (Button) findViewById(R.id.btnlogin);
        tvnewregister = (TextView) findViewById(R.id.tvnewregister);
        //tvyourchoice = (TextView) findViewById(R.id.tvyourchoice);

        btnFBlogin = (LoginButton) findViewById(R.id.btnFBlogin);

        sp = getSharedPreferences(MYPREFERNCES_JOYMEAL, 0);
        editor = sp.edit();
        try {
            PackageInfo info = getPackageManager().getPackageInfo(
                    "app.yourchoice.com.yourchoice",
                    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) {

        }


        //login with facebook
        btnFBlogin.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                GraphRequest request= GraphRequest.newMeRequest(AccessToken.getCurrentAccessToken(),
                        new GraphRequest.GraphJSONObjectCallback() {
                            @Override
                            public void onCompleted(JSONObject object, GraphResponse response) {
                                Log.e("JSON value : ", object.toString());
                                firstName = "";
                                lastName = "";
                                email = "";

                                ID = "";
                                profilePicUrl = "";
                                try{
                                    firstName = object.getString("first_name");
                                    Log.e("firstname", firstName);
                                    lastName = object.getString("last_name");
                                    email = object.getString("email");
                                    Log.e("email", email);
                                    ID = object.getString("id");
                                    Log.e("fb_id",ID);
                                    profilePicUrl = object.getString("picture");

                                    JSONObject jsonObject = new JSONObject(profilePicUrl);
                                    Log.e("json", "" + jsonObject);
                                    JSONObject jobj = jsonObject.getJSONObject("data");
                                    u = jobj.getString("url");
                                    Log.e("jsonimage", u);
                                    /*JSONObject jsonObject = new JSONObject(Profile_PicURL);
                                    Log.e("json_fbdata", "" + jsonObject);
                                    JSONObject jobj = jsonObject.getJSONObject("data");
                                    Log.e("alljsondata","" + jobj);
                                    Profile_PicURL = jobj.getString("url");
                                    Log.e("jsonimage", Profile_PicURL);*/
                                }catch (Exception e){
                                    e.printStackTrace();
                                }



                            }
                        });

                Bundle parameters = new Bundle();
                parameters.putString("fields", "id, first_name, last_name, email, picture");
                request.setParameters(parameters);
                request.executeAsync();
            }

            @Override
            public void onCancel() {
                Toast.makeText(LoginActivity.this, "Login attempt canceled.", Toast.LENGTH_LONG).show();

            }

            @Override
            public void onError(FacebookException error) {
                Log.d("FB error : ", error.toString());
                Toast.makeText(LoginActivity.this, "Login attempt failed.", Toast.LENGTH_LONG).show();
            }
        });

}