目录
  1. WIKI教程
  2. 学习GWT
  3. CellTree

CellTree

介绍 (Introduction)

CellTree小部件表示树的视图。

Class 声明 (Class Declaration)

以下是com.google.gwt.user.cellview.client.CellTree类的声明 - 

public class CellTree
   extends AbstractCellTree
      implements HasAnimation, Focusable

类构造函数 (Class Constructors)

Sr.No. 构造函数和描述
1

CellTree(TreeViewModel viewModel, T rootValue)

构建一个新的CellTree。

2

CellTree(TreeViewModel viewModel, T rootValue, CellTree.Resources resources)

构建一个新的CellTree。

Class Methods

Sr.No. 功能名称和描述
1

protected char getAccessKey()

获取访问密钥。

2

CellTree.NodeAnimation getAnimation()

如果启用了动画，则获取用于打开和关闭此树中节点的动画。

3

int getDefaultNodeSize()

获取每个树节点下要显示的默认最大子项数。

4

TreeNode getRootTreeNode()

获取根TreeNode。

5

int getTabIndex()

获取窗口小部件在选项卡索引中的位置。

6

boolean isAnimationEnabled()

如果启用了动画，则返回true，否则返回false。

7

protected void onBlur()

键盘选定节点失去焦点时调用。

8

void onBrowserEvent(Event event)

收到浏览器事件时触发。

9

protected void onFocus()

键盘选定节点获得焦点时调用。

10

void setAccessKey(char key)

设置小部件的“访问密钥”。

11

void setAnimation(CellTree.NodeAnimation animation)

设置用于打开和关闭此树中节点的动画。

12

void setAnimationEnabled(boolean enable)

启用或禁用动画。

13

void setDefaultNodeSize(int defaultNodeSize)

设置要在每个子节点下显示的默认子项数。

14

void setFocus(boolean focused)

明确关注/取消聚焦此小部件。

15

void setTabIndex(int index)

设置窗口小部件在选项卡索引中的位置。

方法继承 (Methods Inherited)

该类继承以下类中的方法 -

  • com.google.gwt.user.client.ui.UIObject

  • com.google.gwt.user.client.ui.Widget

  • com.google.gwt.user.client.ui.Composite

  • com.google.gwt.user.cellview.client.AbstractCellTree

  • java.lang.Object

CellTree Widget示例

此示例将指导您完成在GWT中显示CellTree Widget的使用的简单步骤。 按照以下步骤更新我们在GWT - Create Application的GWT应用程序GWT - Create Application章节 -

步 描述
1 在com.iowiki包下创建一个名为HelloWorld的项目，如GWT - Create Application一章中所述。
2 修改HelloWorld.gwt.xml ， HelloWorld.css ， HelloWorld.html和HelloWorld.java ，如下所述。 保持其余文件不变。
3 编译并运行应用程序以验证实现的逻辑的结果。

以下是修改后的模块描述符src/com.iowiki/HelloWorld.gwt.xml 。 

<?xml version = "1.0" encoding = "UTF-8"?>
<module rename-to = 'helloworld'>
   <!-- Inherit the core Web Toolkit stuff.                        -->
   <inherits name = 'com.google.gwt.user.User'/>
   <!-- Inherit the default GWT style sheet.                       -->
   <inherits name = 'com.google.gwt.user.theme.clean.Clean'/>
   <!-- Specify the app entry point class.                         -->
   <entry-point class = 'com.iowiki.client.HelloWorld'/>
   <!-- Specify the paths for translatable code                    -->
   <source path ='client'/>
   <source path = 'shared'/>
</module>

以下是修改后的样式表文件war/HelloWorld.css 。 

body {
   text-align: center;
   font-family: verdana, sans-serif;
}
h1 {
   font-size: 2em;
   font-weight: bold;
   color: #777777;
   margin: 40px 0px 70px;
   text-align: center;
}

以下是修改后的HTML主机文件war/HelloWorld.html 。 

<html>
   <head>
      <title>Hello World</title>
      <link rel = "stylesheet" href = "HelloWorld.css"/>
      <script language = "javascript" src = "helloworld/helloworld.nocache.js">
      </script>
   </head>
   <body>
      <h1>CellTree Widget Demonstration</h1>
      <div id = "gwtContainer"></div>
   </body>
</html>

让我们有以下Java文件src/com.iowiki/HelloWorld.java ，它将演示CellTree小部件的使用。 

package com.iowiki.client;
import java.util.ArrayList;
import java.util.List;
import com.google.gwt.cell.client.AbstractCell;
import com.google.gwt.cell.client.Cell;
import com.google.gwt.cell.client.TextCell;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.GWT;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.user.cellview.client.CellTree;
import com.google.gwt.user.cellview.client.
HasKeyboardSelectionPolicy.KeyboardSelectionPolicy;
import com.google.gwt.user.cellview.client.TreeNode;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.VerticalPanel;
import com.google.gwt.view.client.ListDataProvider;
import com.google.gwt.view.client.SingleSelectionModel;
import com.google.gwt.view.client.TreeViewModel;
public class HelloWorld implements EntryPoint {
   /**
    * A list of songs.
    */
   private static class Playlist {
     private final String name;
     private final List<String> songs = new ArrayList<String>();
     public Playlist(String name) {
       this.name = name;
     }
      /**
       * Add a song to the playlist.
       * 
       * @param name the name of the song
       */
      public void addSong(String name) {
         songs.add(name);
      }
      public String getName() {
         return name;
      }
      /**
       * Return the list of songs in the playlist.
       */
      public List<String> getSongs() {
         return songs;
      }
   }
   /**
    * A composer of classical music.
    */
   private static class Composer {
      private final String name;
      private final List<Playlist> playlists = new ArrayList<Playlist>();
      public Composer(String name) {
         this.name = name;
      }
      /**
       * Add a playlist to the composer.
       * 
       * @param playlist the playlist to add
       */
      public Playlist addPlaylist(Playlist playlist) {   
         playlists.add(playlist);
         return playlist;
      }
      public String getName() {
         return name;
      }
      /**
       * Return the rockin' playlist for this composer.
       */
      public List<Playlist> getPlaylists() {
         return playlists;
      }
   }
   /**
    * The model that defines the nodes in the tree.
    */
   private static class CustomTreeModel implements TreeViewModel {
   private final List<Composer> composers;
   /**
    * This selection model is shared across all leaf nodes. 
    * A selection model can also be shared across all nodes 
    * in the tree, or each set of child nodes can have 
    * its own instance. This gives you flexibility to 
    * determine how nodes are selected.
    */
   private final SingleSelectionModel<String> selectionModel 
   = new SingleSelectionModel<String>();
      public CustomTreeModel() {
         // Create a database of information.
         composers = new ArrayList<Composer>();
         // Add compositions by Beethoven.
         {
            Composer beethoven = new Composer("Beethoven");
            composers.add(beethoven);
            Playlist concertos = beethoven.addPlaylist(
            new Playlist("Concertos"));
            concertos.addSong("No. 1 - C");
            concertos.addSong("No. 2 - B-Flat Major");
            concertos.addSong("No. 3 - C Minor");
            concertos.addSong("No. 4 - G Major");
            concertos.addSong("No. 5 - E-Flat Major");
            Playlist quartets = beethoven.addPlaylist(
            new Playlist("Quartets"));
            quartets.addSong("Six String Quartets");
            quartets.addSong("Three String Quartets");
            quartets.addSong("Grosse Fugue for String Quartets");
            Playlist sonatas = beethoven.addPlaylist(
            new Playlist("Sonatas"));
            sonatas.addSong("Sonata in A Minor");
            sonatas.addSong("Sonata in F Major");
            Playlist symphonies = beethoven.addPlaylist(
            new Playlist("Symphonies"));
            symphonies.addSong("No. 2 - D Major");
            symphonies.addSong("No. 2 - D Major");
            symphonies.addSong("No. 3 - E-Flat Major");
            symphonies.addSong("No. 4 - B-Flat Major");
            symphonies.addSong("No. 5 - C Minor");
            symphonies.addSong("No. 6 - F Major");
            symphonies.addSong("No. 7 - A Major");
            symphonies.addSong("No. 8 - F Major");
            symphonies.addSong("No. 9 - D Minor");
         }
         // Add compositions by Brahms.
         {
            Composer brahms = new Composer("Brahms");
            composers.add(brahms);
            Playlist concertos = brahms.addPlaylist(
            new Playlist("Concertos"));
            concertos.addSong("Violin Concerto");
            concertos.addSong("Double Concerto - A Minor");
            concertos.addSong("Piano Concerto No. 1 - D Minor");
            concertos.addSong("Piano Concerto No. 2 - B-Flat Major");
            Playlist quartets = brahms.addPlaylist(
            new Playlist("Quartets"));
            quartets.addSong("Piano Quartet No. 1 - G Minor");
            quartets.addSong("Piano Quartet No. 2 - A Major");
            quartets.addSong("Piano Quartet No. 3 - C Minor");
            quartets.addSong("String Quartet No. 3 - B-Flat Minor");
            Playlist sonatas = brahms.addPlaylist(
            new Playlist("Sonatas"));
            sonatas.addSong("Two Sonatas for Clarinet - F Minor");
            sonatas.addSong("Two Sonatas for Clarinet - E-Flat Major");
            Playlist symphonies = brahms.addPlaylist(
            new Playlist("Symphonies"));
            symphonies.addSong("No. 1 - C Minor");
            symphonies.addSong("No. 2 - D Minor");
            symphonies.addSong("No. 3 - F Major");
            symphonies.addSong("No. 4 - E Minor");
         }
         // Add compositions by Mozart.
         {
            Composer mozart = new Composer("Mozart");
            composers.add(mozart);
            Playlist concertos = mozart.addPlaylist(
            new Playlist("Concertos"));
            concertos.addSong("Piano Concerto No. 12");
            concertos.addSong("Piano Concerto No. 17");
            concertos.addSong("Clarinet Concerto");
            concertos.addSong("Violin Concerto No. 5");
            concertos.addSong("Violin Concerto No. 4");
         }
      }
      /**
       * Get the {@link NodeInfo} that provides the children of the 
       * specified value.
       */
      public <T> NodeInfo<?> getNodeInfo(T value) {
         if (value == null) {
            // LEVEL 0.
            // We passed null as the root value. Return the composers.
            // Create a data provider that contains the list of composers.
            ListDataProvider<Composer> dataProvider 
            = new ListDataProvider<HelloWorld.Composer>(
            composers);
            // Create a cell to display a composer.
            Cell<HelloWorld.Composer> cell 
            = new AbstractCell<HelloWorld.Composer>() {
               @Override
               public void render(Composer value, Object key,
               SafeHtmlBuilder sb) {
                  if (value != null) {
                	 sb.appendHtmlConstant("    "); 
                     sb.appendEscaped(value.getName());
                  }				
               }
            };
            // Return a node info that pairs the data provider and the cell.
            return new DefaultNodeInfo<Composer>(dataProvider, cell);
         } else if (value instanceof Composer) {
            // LEVEL 1.
            // We want the children of the composer. Return the playlists.
            ListDataProvider<HelloWorld.Playlist> dataProvider
            = new ListDataProvider<HelloWorld.Playlist>(
            ((Composer) value).getPlaylists());
            Cell<HelloWorld.Playlist> cell = 
            new AbstractCell<HelloWorld.Playlist>() {
               @Override
               public void render(Playlist value, Object key, SafeHtmlBuilder sb) {
                  if (value != null) {        
                     sb.appendHtmlConstant("    "); 
                     sb.appendEscaped(value.getName());
                  }
               }
            };
            return new DefaultNodeInfo<Playlist>(dataProvider, cell);
         } else if (value instanceof Playlist) {
            // LEVEL 2 - LEAF.
            // We want the children of the playlist. Return the songs.
            ListDataProvider<String> dataProvider 
            = new ListDataProvider<String>(
            ((Playlist) value).getSongs());
            // Use the shared selection model.
            return new DefaultNodeInfo<String>(dataProvider, new TextCell(),
            selectionModel, null);
         }
         return null;
      }
      /**
       * Check if the specified value represents a leaf node. 
       * Leaf nodes cannot be opened.
       */
      public boolean isLeaf(Object value) {
      // The leaf nodes are the songs, which are Strings.
      if (value instanceof String) {
         return true;
      }
      return false;
      }
   }
   public void onModuleLoad() {
      // Create a model for the tree.
      TreeViewModel model = new CustomTreeModel();
      //Get CellTree style using its BasicResources	   
      //CellTree.Resources res = GWT.create(CellTree.BasicResources.class);
      /*
       * Create the tree using the model. We use <code>null</code> 
       * as the default value of the root node. The default value will 
       * be passed to CustomTreeModel#getNodeInfo();
       */
      CellTree tree = new CellTree(model, null);
      tree.setKeyboardSelectionPolicy(KeyboardSelectionPolicy.ENABLED);
      // Open the first playlist by default.
      TreeNode rootNode = tree.getRootTreeNode();
      TreeNode firstPlaylist = rootNode.setChildOpen(0, true);
      firstPlaylist.setChildOpen(0, true);
      VerticalPanel panel = new VerticalPanel();
      panel.setBorderWidth(1);	    
      panel.setWidth("300");
      panel.add(tree);
      // Add the widgets to the root panel.
      RootPanel.get().add(panel);
   }
}

一旦准备好完成所有更改，让我们像在GWT - 创建应用程序章节中那样在开发模式下编译和运行应用程序 。 如果您的应用程序一切正常，这将产生以下结果 -

GWT CellTree小部件
↑回到顶部↑
WIKI教程 @2018