I want to add the navigation drawer functionality to my activity, but the default menu icon on left does not appear although when I swipe right, the drawer opens up. Here's my layout file:
<?xml version="1.0" encoding="utf-8"?> <android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/drawer_layout" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" tools:openDrawer="start"> <android.support.design.widget.CoordinatorLayout android:id="@+id/coordinatorLayout" android:layout_width="match_parent" android:layout_height="match_parent"> <android.support.design.widget.AppBarLayout android:id="@+id/appBarLayout" android:layout_width="match_parent" android:theme="@style/AppTheme.AppBarOverlay" android:layout_height="wrap_content"> <android.support.v7.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:background="?attr/colorPrimary" app:popupTheme="@style/AppTheme.PopupOverlay" app:layout_scrollFlags="scroll|enterAlways" /> <android.support.design.widget.TabLayout android:id="@+id/tabLayout" android:layout_width="match_parent" android:layout_height="wrap_content" app:tabTextColor="@android:color/white" app:tabSelectedTextColor="@android:color/white" app:tabIndicatorColor="@android:color/white" app:tabIndicatorHeight="6dp"/> </android.support.design.widget.AppBarLayout> <android.support.v4.view.ViewPager android:id="@+id/viewPager" android:layout_width="match_parent" android:layout_height="match_parent" app:layout_behavior="@string/appbar_scrolling_view_behavior"/> </android.support.design.widget.CoordinatorLayout> <android.support.design.widget.NavigationView android:id="@+id/nav_view" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_gravity="start" android:fitsSystemWindows="true" app:headerLayout="@layout/nav_header_one_more" app:menu="@menu/activity_one_more_drawer" /> </android.support.v4.widget.DrawerLayout> My Activity file:
public class PartThreeActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener { private DrawerLayout mDrawerLayout; private Toolbar toolbar; @Override protected void onCreate(Bundle savedInstanceState) { setTheme(R.style.AppThemeBlue); super.onCreate(savedInstanceState); setContentView(R.layout.activity_part_three); initToolbar(); initViewPagerAndTabs(); DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); ActionBarDrawerToggle toggle = new ActionBarDrawerToggle( this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); drawer.setDrawerListener(toggle); toggle.syncState(); NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); navigationView.setNavigationItemSelectedListener(this); } private void initToolbar() { Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar); setSupportActionBar(mToolbar); setTitle(getString(R.string.app_name)); mToolbar.setTitleTextColor(getResources().getColor(android.R.color.white)); } private void initViewPagerAndTabs() { ViewPager viewPager = (ViewPager) findViewById(R.id.viewPager); PagerAdapter pagerAdapter = new PagerAdapter(getSupportFragmentManager()); pagerAdapter.addFragment(PartThreeFragment.createInstance(20), getString(R.string.tab_1)); pagerAdapter.addFragment(PartThreeFragment.createInstance(4), getString(R.string.tab_2)); viewPager.setAdapter(pagerAdapter); TabLayout tabLayout = (TabLayout) findViewById(R.id.tabLayout); tabLayout.setupWithViewPager(viewPager); } @Override public void onBackPressed() { DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); if (drawer.isDrawerOpen(GravityCompat.START)) { drawer.closeDrawer(GravityCompat.START); } else { super.onBackPressed(); } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.one_more, 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); } @SuppressWarnings("StatementWithEmptyBody") @Override public boolean onNavigationItemSelected(MenuItem item) { // Handle navigation view item clicks here. int id = item.getItemId(); if (id == R.id.nav_camera) { // Handle the camera action } else if (id == R.id.nav_gallery) { } else if (id == R.id.nav_slideshow) { } else if (id == R.id.nav_manage) { } else if (id == R.id.nav_share) { } else if (id == R.id.nav_send) { } DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); drawer.closeDrawer(GravityCompat.START); return true; } static class PagerAdapter extends FragmentPagerAdapter { private final List<Fragment> fragmentList = new ArrayList<>(); private final List<String> fragmentTitleList = new ArrayList<>(); public PagerAdapter(FragmentManager fragmentManager) { super(fragmentManager); } public void addFragment(Fragment fragment, String title) { fragmentList.add(fragment); fragmentTitleList.add(title); } @Override public Fragment getItem(int position) { return fragmentList.get(position); } @Override public int getCount() { return fragmentList.size(); } @Override public CharSequence getPageTitle(int position) { return fragmentTitleList.get(position); } } } And here are the screenshots: 
Here is the link to my project: https://drive.google.com/open?id=0B6_hNGJUq8_2RUtxTl9pTGlqb2c Please help me find out why the menu is not appearing, thanks.
