java - MigLayout, aligning all components at center of JFrame -

how can align components @ jpanel @ center of jframe.

here codes , got

i want this

mainframe

import javax.swing.jframe; import javax.swing.jpanel;  public class mainframe extends jframe {   private static mainframe instance = new mainframe();  public static mainframe getinstance() {     return instance; }  public static void switchtopanel(jpanel p) {     getinstance().setcontentpane(p);     getinstance().validate(); }  private mainframe() {     settitle("favmovies");     setsize(400, 400);     setlocationrelativeto(null);     setvisible(true);      setdefaultcloseoperation(jframe.exit_on_close);  }  public static void main(string[] args) {     mainframe.switchtopanel(new loginpanel()); } } 

loginpanel

import javax.swing.*; import net.miginfocom.swing.miglayout;    public class loginpanel extends jpanel {  // properties  private jtextfield inputusername; private jpasswordfield inputpassword;  // constructor  public loginpanel() {      setsize(400,400);      // components      inputusername = new jtextfield(10);     inputpassword = new jpasswordfield(10);     jbutton loginbutton = new jbutton("login");     jbutton createbutton = new jbutton( "create user");      setlayout(new miglayout());      // first row     add(new jlabel( "username: "));     add(inputusername, "wrap 5");      // second row     add(new jlabel( "password: "));     add(inputpassword, "wrap 10");      // final row             add(loginbutton);     add(createbutton);    }  } 

i hope explain :( hope explain :( hope explain :( hope explain :(

the gridbaglayout center components automatically. set layout of frame use gridbaglayout , add login panel frame:

//getinstance().setcontentpane(p); getinstance().setlayout( new gridbaglayout() ); getinstance().add(p); 

edit:

however, when resize it, able see loginpanel @ center.

it looks adding component visible gui. need manually invoke layout manager , repaint component.

getinstance().validate(); getinstance().revalidate(); getinstance().repaint(); 

the structure of code complicated. should read swing tutorial better examples , won't have problem. maybe start labeldemo how use labels.

if need ability swap panels, take @ section swing tutorial on how use cardlayout, designed purpose.