Create a JComboBox with icons and indents in Java

Create a default JComboBox cannot display icons, indents, and so on on each entry. But Swing's MVC design architecture provides unmatched scalability for a variety of components. To do this, we can create a new renderer to take care of the drawing of each entry.





First we write a new class Imagedcomboboxitem, which encapsulates information about a Drop-down entry, including icons, text, indents, and so on:





class Imagedcomboboxitem {


private icon icon = null;


private String text = null;


private int indent = 0;





Imagedcomboboxitem (String Text, icon icon, int indent) {


this.text = text;


This.icon = icon;


this.indent = indent;


}





public String GetText () {


return text;


}





public Icon GetIcon () {


return icon;


}





public int getindent () {


return indent;


}


}





Then create a new Jimagedcombobox class and inherit from JComboBox. In the constructor, create a new defaultlistcellrenderer as the renderer and overwrite its Getlistcellrenderercomponent method. In the new Getlistcellrenderercomponent method, the parent object's method is still invoked first to complete the drawing of the normal entry, and then to determine if the entry is a Imagedcomboboxitem instance. If it does, it displays the Imagedcomboboxitem text, icon, and indents. To make it easier to display the left indent, we directly create a emptyborder and set the left indent quantity and set it to the Defaultlistcellrenderer. Defaultlistcellrenderer inherit from JLabel, so can directly accept all kinds of border. Here we take each indentation of 10 pixels as an example.





Well, here's the complete code:





import java.util.*;





import java.awt.*;


import javax.swing.*;





public class Jimagedcombobox extends JComboBox {


public Jimagedcombobox (Vector values) {


super (values);


listcellrenderer renderer = new Defaultlistcellrenderer () {


public Component getlistcellrenderercomponent (


JList list,


Object value,


int index,


Boolean isselected,


Boolean cellhasfocus) {


super.getlistcellrenderercomponent (list, value, index, isselected, cellhasfocus);


if (value instanceof Imagedcomboboxitem) {


Imagedcomboboxitem item = (imagedcomboboxitem) value;


This.settext (Item.gettext ());


This.seticon (Item.geticon ());


if (ispopupvisible ()) {


int offset = ten * item.getindent ();


This.setborder (borderfactory.createemptyborder (0, offset, 0, 0));


}


}


return to this;


}


};


this.setrenderer (renderer);


}





public static void Main (string[] args) {


JFrame frame = new JFrame ();


frame.setsize (400, 400);


vector values = new vector ();


Icon Openicon = new ImageIcon (JImagedComboBox.class.getResource ("open16.gif"));


Icon Newicon = new ImageIcon (JImagedComboBox.class.getResource ("new16.gif"));


for (int i = 0; i < 5; i++) {


values.addelement (New Imagedcomboboxitem ("Directory" + I, Openicon, i));


}


for (int i = 0; i < 5; i++) {


values.addelement (New Imagedcomboboxitem ("Image Item" + I, Newicon, 5));


}


Jimagedcombobox ComboBox = new Jimagedcombobox (values);


Frame.getcontentpane (). Add (ComboBox, Borderlayout.north);


frame.show ();


}


}





class Imagedcomboboxitem {


private icon icon = null;


private String text = null;


private int indent = 0;





Imagedcomboboxitem (String Text, icon icon, int indent) {


this.text = text;


This.icon = icon;


this.indent = indent;


}





public String GetText () {


return text;


}





public Icon GetIcon () {


return icon;


}





public int getindent () {


return indent;


}


}





of which, two icons are here: Open16.gif,new16.gif