In this example we shall show you how to create a ListBox example using the Google Web Toolkit, that is an open source set of tools that allows web developers to create and maintain complex JavaScript front-end applications in Java. A BoxList is a widget that presents a list of choices to the user, either as a list box or as a drop-down list. To create a ListBox example we have performed the following steps:
- The
ListBoxExampleclass implements thecom.google.gwt.core.client.EntryPointinterface to allow the class to act as a module entry point. It overrides itsonModuleLoad()method. - Create a new Horizontal panel.
- Create a ListBox that is a Drop Down List. Add Items to the ListBox.
- Create a new ListBox that displays categories contents. Add Items to this ListBox too.
- Add a ChangeHandler to dropDownList. Override its
onChange(ChangeEvent event)method to handle the change events fire. - Add the boxLists to the HorizontalPanel.
- Add the HorizontalPanel to the
RootPanel, that is the panel to which all other widgets must ultimately be added,
as described in the code snippet below.
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 | package com.javacodegeeks.snippets.enterprise;import com.google.gwt.core.client.EntryPoint;import com.google.gwt.event.dom.client.ChangeEvent;import com.google.gwt.event.dom.client.ChangeHandler;import com.google.gwt.user.client.ui.HorizontalPanel;import com.google.gwt.user.client.ui.ListBox;import com.google.gwt.user.client.ui.RootPanel;public class ListBoxExample implements EntryPoint { // Constants final String[] Items = { "Item 0", "Item 1", "Item 2" }; final String[] Item0 = { "Item 0,0", "Item 0,1", "Item 0,2" }; final String[] Item1 = { "Item 1,0", "Item 1,1", "Item 1,2" }; final String[] Item2 = { "Item 2,0", "Item 2,1", "Item 2,2" }; @Override public void onModuleLoad() { // Create new Horizontal panel HorizontalPanel hp = new HorizontalPanel(); hp.setSpacing(20); // Create a ListBox - Drop Down List final ListBox dropDownList = new ListBox(); // Add Items' categories for (int i = 0; i < Items.length; i++) { dropDownList.addItem(Items[i]); } // Create new ListBox that displays categories contents final ListBox contentList = new ListBox(); contentList.setVisibleItemCount(5); // Initialize the List with data from Item0 for (int i = 0; i < Item0.length; i++) { contentList.addItem(Item0[i]); } // Add ChangeHandler to dropDownList dropDownList.addChangeHandler(new ChangeHandler() { @Override public void onChange(ChangeEvent event) { // Get the index of the selected Item int Item = dropDownList.getSelectedIndex(); String[] listData = null; // Clear the content list contentList.clear(); // Set content switch (Item) { case 0: listData = Item0; break; case 1: listData = Item1; break; case 2: listData = Item2; break; } for (int i = 0; i < listData.length; i++) { contentList.addItem(listData[i]); } } }); // Add widgets to Vertical Panel hp.add(dropDownList); hp.add(contentList); // Add Vertical Panel to Root Panel RootPanel.get().add(hp); }} |
This was an example of how to create a ListBox example.
