LoginActivity

package com.example.ratih.mtf_go_scanner_java;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.content.SharedPreferences;

import com.example.ratih.mtf_go_scanner_java.api.ApiHelper;
import com.example.ratih.mtf_go_scanner_java.api.req.LoginReq;
import com.example.ratih.mtf_go_scanner_java.api.resp.BaseResp;
import com.example.ratih.mtf_go_scanner_java.api.resp.LoginResp;
import com.google.gson.Gson;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;

public class LoginActivity extends AppCompatActivity {

    Button btnLogin;
    EditText edUname, edPass;
    ApiHelper apiHelper;
    SessionManager session;
    public static final String TAG = "MTF-GO";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        btnLogin = (Button) findViewById(R.id.btnLogin);
        edUname = (EditText) findViewById(R.id.edUname);
        edPass = (EditText) findViewById(R.id.edPass);
        session = new SessionManager(getApplicationContext());

        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                login();
            }
        });

        if(session.isLoggedIn()){
            startActivity(new Intent(LoginActivity.this, MainActivity.class));
            finish();
        }
    }

    public void login() {
        Log.d(TAG, "Login");

        if (validate() == false) {
            onLoginFailed();
            return;
        }
        requestLogin();
    }


    private void requestLogin() {
        final String username = edUname.getText().toString();
        String password = edPass.getText().toString();
        apiHelper = ApiHelper.getInstance();

        Call<BaseResp<LoginResp>> call = apiHelper.login(username, password);
        call.enqueue(new Callback<BaseResp<LoginResp>>() {
            @Override
            public void onResponse(Call<BaseResp<LoginResp>> call, Response<BaseResp<LoginResp>> response) {
                if (response.isSuccessful()) {
                    if (response.body().isSuccess()) {
                        String id = response.body().getData().getId();
                        String token = response.body().getData().getToken();
                        session.savePrefString(SessionManager.KEY_ID,id);
                        session.savePrefString(SessionManager.KEY_TOKEN,token);
                        session.savePrefBoolean(SessionManager.IS_LOGIN, true);
                        startActivity(new Intent(LoginActivity.this, MainActivity.class));
                        Toast.makeText(LoginActivity.this, "Succesfully login", Toast.LENGTH_SHORT).show();
                        finish();
                    } else if (response.body().isNotFound() && response.body().isTokenExpired()){
                        Toast.makeText(getBaseContext(), "Username or password is incorrect", Toast.LENGTH_SHORT).show();
                        btnLogin.setEnabled(true);
                    }
                } else {
                    Log.d("onResponse", "" + response.body().getMessage());
                    Toast.makeText(LoginActivity.this, "Please try again", Toast.LENGTH_SHORT).show();
                }
            }

            @Override
            public void onFailure(Call<BaseResp<LoginResp>> call, Throwable t) {
                Log.e("debug", "onFailure: ERROR > " + t.toString());
            }
        });
    }

    public void onLoginFailed() {
        Toast.makeText(getBaseContext(), "Login failed", Toast.LENGTH_LONG).show();

        btnLogin.setEnabled(true);
    }

    public boolean validate() {
        boolean valid = true;

        String username = edUname.getText().toString();
        String password = edPass.getText().toString();

        if (username.isEmpty()) {
            edUname.setError("Username is empty");
            valid = false;
        } else {
            edUname.setError(null);
        }

        if (password.isEmpty()) {
            edPass.setError("Password is empty");
            valid = false;
        } else {
            edPass.setError(null);
        }

        return valid;
    };


}