swing - Making A Form in Java -

import java.awt.flowlayout; import java.awt.gridbagconstraints; import java.awt.gridbaglayout; import java.awt.event.actionlistener; import java.awt.event.actionevent;  import javax.swing.buttongroup; import javax.swing.jbutton; import javax.swing.jframe; import javax.swing.jlabel; import javax.swing.joptionpane; import javax.swing.jradiobutton; import javax.swing.swingconstants; import javax.swing.jtextfield; import javax.swing.jpasswordfield;  public class loginpanel extends jframe {      private jlabel label1;     private jlabel label2;     private jlabel label3;     private jtextfield usr;     private jpasswordfield pass;     private jbutton submit;     private jradiobutton admin;     private jradiobutton student;     private buttongroup type;      public loginpanel()      {         super("user login");         setdefaultcloseoperation( jframe.exit_on_close );         setsize( 350, 200 ); // set frame size          fieldhandler handler = new fieldhandler();           setlayout(new gridbaglayout());         setresizable(false);          gridbagconstraints c = new gridbagconstraints();          label3 = new jlabel();         label3.settext("login");         c.weightx =0;         c.gridx = 1;         c.gridy = 0;         c.gridwidth = 1;         c.fill = gridbagconstraints.vertical;         add(label3,c);          label1 = new jlabel("username:");         c.weightx = 0;         c.gridx = 0;         c.gridy = 2;         c.gridwidth = 1;         c.fill = gridbagconstraints.horizontal;         add(label1,c);          usr = new jtextfield(10);         c.weightx = 0;         c.gridx = 2;         c.gridy = 2;         c.ipadx = 2;          add(usr,c);          label2 = new jlabel("password:");         c.weightx = 0;         c.gridx = 0;         c.gridy = 3;         c.gridwidth = 1;         c.fill = gridbagconstraints.horizontal;         add(label2,c);          pass = new jpasswordfield(10);         c.weightx = 0;         c.gridx = 2;         c.gridy = 3;         c.ipadx= 2;         add(pass,c);          admin = new jradiobutton( "admin", true );         c.weightx = 0;         c.gridx = 0;         c.gridy = 4;         add(admin,c);          student = new jradiobutton( "student", false );         c.weightx = 0;         c.gridx = 1;         c.gridy = 4;         add(student,c);          submit = new jbutton("submit");         c.weightx = 0;         c.gridx = 1;         c.gridy = 5;         add(submit,c);          type = new buttongroup();         type.add(admin);         type.add(student);          usr.addactionlistener( handler );         pass.addactionlistener( handler );         submit.addactionlistener(handler);      }      class fieldhandler implements actionlistener{          public void actionperformed(actionevent event)  {             string string ="";             if(event.getsource() == usr){                 string = string.format("%s",event.getactioncommand());              }             else if(event.getsource() == pass){                 string = string.format("%s",event.getactioncommand());              }             else if(event.getsource() == submit){                 string = "submit button";              }             joptionpanel.showmessagedialog( null, string );         }      }  } 

i trying make online examination system in java, , new language. have made neat form, text fields, radio buttons, , submit button. checked out event handler functions, , pretty stuck right now. event handler invokes element has operation on it.thats pretty fine, cannot find way data on every element. event.getactioncommand() gets information of element invoked handler. thing not sure how change frame after results database fetched successfully, , if password mismatches or no such user found shows error message(i know done joptionpanel) , returns.

the class has main function is

import java.awt.gridbaglayout; import javax.swing.jframe;  public class start {      public static void main(string args[]) {         loginpanel login = new loginpanel();         login.setvisible( true ); // display frame     }  } 

the fieldhandler inner class of loginpanel. has access fields of loginpanel:

class fieldhandler implements actionlistener{      public void actionperformed(actionevent event)  {         if (event.getsource() == submit){             string user = usr.gettext();              // or string user = loginpanel.this.usr.gettext();              char[] password = pass.getpassword();             // whatever want user , password         }         ...     }  } 

learn nested classes in the java tutorial (which covers swing in depth, way).

it's practice use separate class every listener rather unique class long chain of if blocks testing event comes from.