I managed to make a navigation drawer and trying to get a button working now.
Code:
public class FourthFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fourth_layout, container, false);
    }
    public void buttona1(View view){
        Intent browserIntent = new Intent(Intent.ACTION_VIEW,
                                          Uri.parse("https://www.google.nl"));
        startActivity(browserIntent);
    }
}
Layout:
<Button
    android:text="Magister"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="buttona1"
    android:id="@+id/button2"
    android:visibility="visible"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_alignParentTop="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true" />
The problem is that when I open the app in my mobile and move to the button page, push the button the app will close and stop working.
 
     
     
    