Open screen inside the mainactivity

To do this, you should not start a new activity when you click an item in the navigation drawer. What you should do is work with fragments in MainActivity and replace that fragment when an item is selected instead of starting a new activity.

In your activity_main.xml

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

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

    <FrameLayout
        android:id="@+id/frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </FrameLayout>

</LinearLayout>

<android.support.design.widget.NavigationView
    android:id="@+id/navigation_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true"
    app:theme="@style/NavigationDrawerStyle"
    app:menu="@menu/drawer">

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

In your MainActivity

    navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {

        // This method will trigger on item Click of navigation menu
        @Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {


            //Checking if the item is in checked state or not, if not make it in checked state
            if (menuItem.isChecked()) menuItem.setChecked(false);
            else menuItem.setChecked(true);

            //Closing drawer on item click
            drawerLayout.closeDrawers();
            FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();

            //Check to see which item was being clicked and perform appropriate action
            switch (menuItem.getItemId()) {

                //Replacing the main content with right fragment;
                case R.id.start:
                    if (startfragment == null) {
                        startfragment = new StartFragment();
                    }
                    fragmentTransaction.replace(R.id.frame, startfragment);
                    fragmentTransaction.commit();
                    return true;

                case R.id.second:
                    if (secondfragment == null) {
                        secondfragment = new Secondfragment();
                    }
                    fragmentTransaction.replace(R.id.frame, secondfragment);
                    fragmentTransaction.commit();
                    return true;

                default:
                    if (startfragment == null) {
                        startfragment = new StartFragment();
                    }
                    fragmentTransaction.replace(R.id.frame, startfragment);
                    fragmentTransaction.commit();
                    return true;


            }
         }
    });

And the template of a fragment

public class StartFragment extends Fragment {     // Ui Elements

//Atributtes
private View view;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    view = inflater.inflate(R.layout.fragment_start, container, false);
    return view;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

}}