NavigationDrawerActivity

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.GridView;
import android.widget.TextView;
import android.widget.Toast;

public class NavigationDrawerActivity extends AppCompatActivity {
    private NavigationView navigationView;
    private DrawerLayout drawerLayout;
    private Toolbar toolbar;
    private GridView gridView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_navigation_drawer);
        setTitle("NAVIGATION DRAWER");

        navigationView = findViewById(R.id.navigation_view);
        drawerLayout = findViewById(R.id.drawer);
        toolbar = findViewById(R.id.toolbar);
        gridView = findViewById(R.id.gridView);

        //set item yang sedang dipilih
        navigationView.setCheckedItem(R.id.item_home);
        navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
                drawerLayout.closeDrawers();
                switch (menuItem.getItemId()) {
                    case R.id.item_home:
                        Intent intent = new Intent(getApplicationContext(), RetrofitActivity.class);
                        startActivity(intent);
                        return true;
                    case R.id.item_contact_list:
                        Intent intent1 = new Intent(getApplicationContext(), FinalProjectActivity.class);
                        startActivity(intent1);
                        finish();
                        return true;
                    case R.id.item_camera:
                        Intent intent2 = new Intent(getApplicationContext(), CameraActivity.class);
                        startActivity(intent2);
                        return true;
                    default:
                        return true;
                }
            }
        });
        ActionBarDrawerToggle actionBarDrawerToggle =
                new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.openDrawer, R.string.closeDrawer) {
                    @Override
                    public void onDrawerOpened(View drawerView) {
                        super.onDrawerOpened(drawerView);
                    }

                    @Override
                    public void onDrawerClosed(View drawerView) {
                        super.onDrawerClosed(drawerView);
                    }
                };
        drawerLayout.addDrawerListener(actionBarDrawerToggle);
        actionBarDrawerToggle.syncState();

        //Setting nama dan profile di header
        View view = navigationView.getHeaderView(0);
        TextView textName = view.findViewById(R.id.textName);
        TextView textProfile = view.findViewById(R.id.textProfile);
        textName.setText("AHMAD FAUZI");
        textProfile.setText("Karyawan Swasta");
        GridViewExample();

        //proses menampung intent extra yang dilempar ke activity NavigationDrawer
        String userid = getIntent().getStringExtra("userid_intent");
        Integer angka = getIntent().getIntExtra("integer_intent", 0);
        Toast.makeText(this, String.valueOf(angka), Toast.LENGTH_LONG).show();
    }

    private void GridViewExample() {
        final String[] alphabets = new String[]{
                "A", "B", "C", "D",
                "E", "F", "G", "H",
                "I", "J", "K", "L",
                "M", "N", "O", "P",
                "Q", "R", "S", "T",
                "U", "V", "W", "X",
                "Y", "Z"};
        ArrayAdapter<String> adapter =
                new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, alphabets);
        gridView.setAdapter(adapter);
        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(getApplicationContext(), ((TextView) view).getText(), Toast.LENGTH_SHORT).show();
            }
        });
    }

}