| <?xml version="1.0" encoding="UTF-8"?> |
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| |
| <document id="list-buttons"> |
| <properties> |
| <title>List Buttons</title> |
| </properties> |
| |
| <body> |
| <p>The following example demonstrates use of the <tt>ListButton</tt> component. Selecting an image name from the drop-down shows the corresponding image file in the image view on the right.</p> |
| |
| <application class="org.apache.pivot.wtk.ScriptApplication" |
| width="480" height="340"> |
| <libraries> |
| <library>core</library> |
| <library>wtk</library> |
| <library>wtk-terra</library> |
| <library>tutorials</library> |
| </libraries> |
| <startup-properties> |
| <src>/org/apache/pivot/tutorials/lists/list_buttons.bxml</src> |
| </startup-properties> |
| </application> |
| |
| <p> |
| The BXML source for the example is below. Like the previous example, list data is |
| specified as an attribute containing a JSON array of strings; this value is used to |
| load the image displayed to the right of the list button. Like <tt>ListView</tt>, |
| <tt>ListButtons</tt> can also be populated programmatically using instances of |
| <tt>ListItem</tt>. |
| </p> |
| |
| <source type="xml" location="org/apache/pivot/tutorials/lists/list_buttons.bxml"> |
| <![CDATA[ |
| <lists:ListButtons title="List Buttons" maximized="true" |
| xmlns:bxml="http://pivot.apache.org/bxml" |
| xmlns:lists="org.apache.pivot.tutorials.lists" |
| xmlns="org.apache.pivot.wtk"> |
| <TablePane styles="{showHorizontalGridLines: true, showVerticalGridLines:true, |
| horizontalSpacing:1, verticalSpacing:1}"> |
| <columns> |
| <TablePane.Column width="-1"/> |
| <TablePane.Column width="1*"/> |
| </columns> |
| |
| <TablePane.Row height="340"> |
| <BoxPane orientation="vertical" styles="{verticalAlignment:'top', padding: 4}"> |
| <Label text="Picture:"/> |
| <ListButton bxml:id="listButton" |
| listData="['IMG_0725_2.jpg', 'IMG_0735_2.jpg', 'IMG_0767_2.jpg']"/> |
| </BoxPane> |
| |
| <ImageView bxml:id="imageView" styles="{backgroundColor:'#404040'}"/> |
| </TablePane.Row> |
| </TablePane> |
| </lists:ListButtons> |
| ]]> |
| </source> |
| |
| <p> |
| The Java source for the example is below: |
| </p> |
| |
| <source type="java" location="org/apache/pivot/tutorials/lists/ListButtons.java"> |
| <![CDATA[ |
| package org.apache.pivot.tutorials.lists; |
| |
| import java.net.URL; |
| |
| import org.apache.pivot.beans.Bindable; |
| import org.apache.pivot.collections.Map; |
| import org.apache.pivot.util.Resources; |
| import org.apache.pivot.util.concurrent.TaskExecutionException; |
| import org.apache.pivot.wtk.ApplicationContext; |
| import org.apache.pivot.wtk.ImageView; |
| import org.apache.pivot.wtk.ListButton; |
| import org.apache.pivot.wtk.ListButtonSelectionListener; |
| import org.apache.pivot.wtk.Window; |
| import org.apache.pivot.wtk.media.Image; |
| |
| public class ListButtons extends Window implements Bindable { |
| private ListButton listButton = null; |
| private ImageView imageView = null; |
| |
| @Override |
| public void initialize(Map<String, Object> namespace, URL location, Resources resources) { |
| listButton = (ListButton)namespace.get("listButton"); |
| imageView = (ImageView)namespace.get("imageView"); |
| |
| listButton.getListButtonSelectionListeners().add(new ListButtonSelectionListener.Adapter() { |
| @Override |
| public void selectedItemChanged(ListButton listButton, Object previousSelectedItem) { |
| Object selectedItem = listButton.getSelectedItem(); |
| |
| if (selectedItem != null) { |
| // Get the image URL for the selected item |
| ClassLoader classLoader = Thread.currentThread().getContextClassLoader(); |
| URL imageURL = classLoader.getResource("org/apache/pivot/tutorials/" + selectedItem); |
| |
| // If the image has not been added to the resource cache yet, |
| // add it |
| Image image = (Image)ApplicationContext.getResourceCache().get(imageURL); |
| |
| if (image == null) { |
| try { |
| image = Image.load(imageURL); |
| } catch (TaskExecutionException exception) { |
| throw new RuntimeException(exception); |
| } |
| |
| ApplicationContext.getResourceCache().put(imageURL, image); |
| } |
| |
| // Update the image |
| imageView.setImage(image); |
| } |
| } |
| }); |
| |
| listButton.setSelectedIndex(0); |
| } |
| } |
| ]]> |
| </source> |
| |
| <p> |
| This example makes use of the global resource cache to store the loaded images. |
| This cache can be used to store any kind of application-specific data that may |
| be expensive to load. Entries are keyed by the URL from which they were retrieved, and, |
| once placed in the cache, are available to all code within the application. When the |
| list button's selection changes, the application first looks for an image in the |
| resource cache; if it is not found, it is loaded and added to the cache. |
| It is then set as the "image" property of the image view and displayed. |
| Note that the global cache does not have a way to limiting the number of elements |
| to contain, so the cache continues to grow; to keep it small you have |
| to manually remove old elements from it when they are no more necessary. |
| </p> |
| </body> |
| </document> |
