Navigation Drawer in Android Studio

package com.abc.navigationdrawer;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    DrawerLayout drawerLayout;
    Toolbar toolbar;
    ActionBar actionBar;
    TextView textView;

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

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        actionBar = getSupportActionBar();
        actionBar.setHomeAsUpIndicator(R.drawable.ic_menu_white_24dp);
        actionBar.setDisplayHomeAsUpEnabled(true);

        drawerLayout = (DrawerLayout) findViewById(R.id.navigation_drawer_layout);

        NavigationView navigationView = (NavigationView) findViewById(R.id.navigation_view);
        if (navigationView != null) {
            setupNavigationDrawerContent(navigationView);
        }

        setupNavigationDrawerContent(navigationView);

    }



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                drawerLayout.openDrawer(GravityCompat.START);
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private void setupNavigationDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        textView = (TextView) findViewById(R.id.textView);
                        switch (menuItem.getItemId()) {
                            case R.id.item_navigation_drawer_inbox:
                                menuItem.setChecked(true);
                                textView.setText(menuItem.getTitle());
                                drawerLayout.closeDrawer(GravityCompat.START);
                                return true;
                            case R.id.item_navigation_drawer_starred:
                                menuItem.setChecked(true);
                                textView.setText(menuItem.getTitle());
                                drawerLayout.closeDrawer(GravityCompat.START);
                                return true;
                            case R.id.item_navigation_drawer_sent_mail:
                                menuItem.setChecked(true);
                                textView.setText(menuItem.getTitle());
                                drawerLayout.closeDrawer(GravityCompat.START);
                                return true;
                            case R.id.item_navigation_drawer_drafts:
                                menuItem.setChecked(true);
                                textView.setText(menuItem.getTitle());
                                drawerLayout.closeDrawer(GravityCompat.START);
                                return true;
                            case R.id.item_navigation_drawer_settings:
                                menuItem.setChecked(true);
                                textView.setText(menuItem.getTitle());
                                Toast.makeText(MainActivity.this, "Launching " + menuItem.getTitle().toString(), Toast.LENGTH_SHORT).show();
                                drawerLayout.closeDrawer(GravityCompat.START);
                                Intent intent = new Intent(MainActivity.this, SettingsActivity.class);
                                startActivity(intent);
                                return true;
                            case R.id.item_navigation_drawer_help_and_feedback:
                                menuItem.setChecked(true);
                                Toast.makeText(MainActivity.this, menuItem.getTitle().toString(), Toast.LENGTH_SHORT).show();
                                drawerLayout.closeDrawer(GravityCompat.START);
                                return true;
                        }
                        return true;
                    }
                });
    }
}

package com.abc.navigationdrawer;

import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.util.TypedValue;
import android.view.Menu;
import android.view.MenuItem;

public class SettingsActivity extends AppCompatActivity {

    Toolbar toolbar;

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

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        TypedValue typedValueColorPrimaryDark = new TypedValue();
        SettingsActivity.this.getTheme().resolveAttribute(R.attr.colorPrimaryDark, typedValueColorPrimaryDark, true);
        final int colorPrimaryDark = typedValueColorPrimaryDark.data;
        if (Build.VERSION.SDK_INT >= 21) {
            getWindow().setStatusBarColor(colorPrimaryDark);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_settings, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}