Android Navigation Drawer not slide out

Question

I am messing around with the Material Navigation Drawer, but its not sliding out. When I press the top left drawer icon, the Navigation Drawer does not pop out. I can't figure out what I am missing.

It slides out correctly when I swipe left to right on the screen. But it doesn't show up by clicking the drawer icon at the top left corner.

Here is part of my Activity:

public class MainActivity extends AppCompatActivity {
    private DrawerLayout drawerLayout;
    private Toolbar toolbar;
    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        initNavigationDrawer();
    }

    public void initNavigationDrawer() {

        NavigationView navigationView = (NavigationView)findViewById(R.id.navigation_view);
        navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {

                int id = menuItem.getItemId();

                switch (id){
                    case R.id.home:
                        Toast.makeText(getApplicationContext(),"Home", Toast.LENGTH_SHORT).show();
                        drawerLayout.closeDrawers();
                        break;
                    case R.id.settings:
                        Toast.makeText(getApplicationContext(),"Settings",Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.logout:
                        finish();
                }
                return true;
            }
        });

        View header = navigationView.getHeaderView(0);
        TextView tv_email = (TextView)header.findViewById(R.id.tv_email);
        tv_email.setText("raj.amalw@learn2crack.com");
        drawerLayout = (DrawerLayout)findViewById(R.id.drawer);

        ActionBarDrawerToggle actionBarDrawerToggle = new ActionBarDrawerToggle(this,drawerLayout,toolbar,R.string.drawer_open,R.string.drawer_close){

            @Override
            public void onDrawerClosed(View v){
                super.onDrawerClosed(v);
            }

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

Here is the activity_main:

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

<android.support.design.widget.CoordinatorLayout 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/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="garagemonitor.studiosunmedia.garage.MainActivity">
        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/AppTheme.AppBarOverlay">

        <include
            android:id="@+id/toolbar"
            layout="@layout/tool_bar">
        </include>

    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="@dimen/fab_margin"
        android:visibility="invisible"
        android:src="@android:drawable/ic_dialog_email" />
</android.support.design.widget.CoordinatorLayout>
    <android.support.design.widget.NavigationView
        android:id="@+id/navigation_view"
        android:layout_height="match_parent"
        android:layout_width="wrap_content"
        android:layout_gravity="start"
        app:headerLayout="@layout/nav_header"
        app:menu="@menu/menu_navigation"/>
</android.support.v4.widget.DrawerLayout>

Toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?attr/colorPrimary"
    android:theme="@style/ThemeOverlay.AppCompat.Dark"
    android:elevation="4dp">

</android.support.v7.widget.Toolbar>

Answer 1

In your code, above setSupportActionBar(toolbar), use

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

instead of:

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

You are reinitializing toolbar variable there, what causes that in onCreate method you are using other toolbar variable than in initNavigationDrawer.

Answer 2

Try adding the logic manually:

toolbar.setNavigationOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        drawerLayout.openDrawer(GravityCompat.START);
    }
});

This should work.