java - Stepped ComboBox refresh -

a stepped combobox useful make drop-down pop-up wider text field. when new content added list, pop-up gets initial width back.

by default

after refresh (new element)

sscce

import java.awt.dimension; import java.awt.flowlayout; import java.awt.rectangle; import java.awt.event.actionevent; import java.awt.event.actionlistener; import java.awt.event.windowadapter; import java.awt.event.windowevent; import java.util.arraylist; import java.util.arrays; import java.util.list; import java.util.vector;  import javax.swing.comboboxmodel; import javax.swing.defaultcomboboxmodel; import javax.swing.jbutton; import javax.swing.jcombobox; import javax.swing.jframe; import javax.swing.plaf.basic.basiccombopopup; import javax.swing.plaf.basic.combopopup; import javax.swing.plaf.metal.metalcomboboxui;  public class steppedcomboboxrefresh extends jframe {     private list<string> list;     private final steppedcombobox combo;      public steppedcomboboxrefresh() {         super("steppedcombobox refresh");          this.list = new arraylist<string>(arrays.aslist(new string[]{                 "aaa", "aaaaaa"         }));          this.combo = new steppedcombobox(this.list.toarray());         this.combo.setdimensions(50);          jbutton addbutton = new jbutton("add longer string");         addbutton.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent e) {                 list.add(list.get(list.size()-1) + "aaa");                 combo.setmodel(new defaultcomboboxmodel(list.toarray()));                 combo.setdimensions(50);             }         });          getcontentpane().setlayout(new flowlayout());         getcontentpane().add(this.combo);         getcontentpane().add(addbutton);     }      public static void main (string args[]) {         steppedcomboboxrefresh f = new steppedcomboboxrefresh();         f.addwindowlistener(new windowadapter() {             @override             public void windowclosing(windowevent e) {                 system.exit(0);             }         });         f.setsize (300, 100);         f.setvisible(true);     } }  class steppedcomboboxui extends metalcomboboxui {     @override     protected combopopup createpopup() {         basiccombopopup popup = new basiccombopopup( this.combobox ) {              @override             public void show() {                 dimension popupsize = ((steppedcombobox)this.combobox).getpopupsize();                 popupsize.setsize( popupsize.width,                         getpopupheightforrowcount( this.combobox.getmaximumrowcount() ) );                 rectangle popupbounds = computepopupbounds( 0,                         this.combobox.getbounds().height, popupsize.width, popupsize.height);                 this.scroller.setmaximumsize( popupbounds.getsize() );                 this.scroller.setpreferredsize( popupbounds.getsize() );                 this.scroller.setminimumsize( popupbounds.getsize() );                 this.list.invalidate();                 int selectedindex = this.combobox.getselectedindex();                 if ( selectedindex == -1 ) {                     this.list.clearselection();                 } else {                     this.list.setselectedindex( selectedindex );                 }                 this.list.ensureindexisvisible( this.list.getselectedindex() );                 setlightweightpopupenabled( this.combobox.islightweightpopupenabled() );                  show( this.combobox, popupbounds.x, popupbounds.y );             }         };         popup.getaccessiblecontext().setaccessibleparent(this.combobox);         return popup;     } }  class steppedcombobox extends jcombobox {     protected int popupwidth;      public steppedcombobox(comboboxmodel amodel) {         super(amodel);         setui(new steppedcomboboxui());         this.popupwidth = 0;     }      public steppedcombobox(final object[] items) {         super(items);         setui(new steppedcomboboxui());         this.popupwidth = 0;     }      public steppedcombobox(vector items) {         super(items);         setui(new steppedcomboboxui());         this.popupwidth = 0;     }      public void setpopupwidth(int width) {         this.popupwidth = width;     }      public dimension getpopupsize() {         dimension size = getsize();         if (this.popupwidth < 1) {             this.popupwidth = size.width;         }         return new dimension(this.popupwidth, size.height);     }      public void setdimensions(int width) {         dimension d = getpreferredsize();         setpreferredsize(new dimension(width, d.height));         setpopupwidth(d.width);     } } 

you use combo box popup.

it more flexible version of stepped combo box. best of can used on combo box since logic implemented in `popupmenulistener'.

you can control maximum width of popup. can have popup display above combo box instead of below.