Sliding navigation drawer not handling clicks on menu items android

Your DrawerLayout's child Views are incorrectly z-ordered. The View for the drawer - in this case, the ListView - needs to be listed last in order to be on top of everything else.

Do it Simple like this: Add these line of code after setContentView(R.layout.activity_main); or what ever your activity name is.

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

    // Initializing Drawer Layout and ActionBarToggle
    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){

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

        @Override
        public void onDrawerOpened(View drawerView) {
            super.onDrawerOpened(drawerView);
        }
    };
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
    navigationView.bringToFront();

Then Move to next step:

@Override
public boolean onNavigationItemSelected(MenuItem item) {
    displaySelectedScreen(item.getItemId());
    return true;
}
private void displaySelectedScreen(int itemId){
    try {
        switch (itemId) {
            case R.id.nav_menu1:
                startActivity(new Intent(this, BActivity.class));
                break;
            case R.id.nav_menu2:
                startActivity(new Intent(this, CActivity.class));
                break;
        }

    }
    catch (Exception e)
    {
        e.printStackTrace();
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer);
    drawer.closeDrawer(GravityCompat.START);
}