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<h1>NetBeans Nodes, Explorer Manager, and Component Palette Tutorial</h1>

<p>In this tutorial, you will learn how to create a BeanTreeView with drag and drop
 functionality. You will view the nodes in a variety of explorer views and create
 a Component Palette containing items created from your nodes.</p>

<p>The main points of this tutorial are threefold:</p>

 <ul>
     <li>To demonstrate how a fully functional yet simple BeanTreeView is created.</li>
     <li>To demonstrate a key feature in the NetBeans APIs, that of loosely coupled views.</li>
     <li>To demonstrate how nodes can be turned into items in a Component Palette,
         without the intervention of a <tt>layer.xml</tt> file.</li>
 </ul>

 <p>Once this tutorial is finished, you will have a BeanTreeView that provides
  the following menu items, in addition to the support for dragging and dropping
  the child nodes:</p>
 
<p><img alt="" src="../../images/tutorials/nodes-3/final-result.png"/></p>

<p>You will be shown how to change the explorer view from BeanTreeView
 to MenuView, ListView, and several other views supported
 by the <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/overview-summary.html">Explorer and Property Sheet API</a>.</p>

<p>This is what the completed project will look like in the Projects window:</p>

<p><img alt="" src="../../images/tutorials/nodes-3/projects-window.png"/></p>


<!-- ===================================================================================== -->

<h3 class="tutorial"><a name="installing-software"></a>Installing the Software</h3>
   
    
      <p>Before you begin, you need to install the following software on your 
        computer:</p>
<ul>
     <li>NetBeans IDE version 6.7 or above.</li>
     <li>Java Standard Development Kit (JDK&trade;) version
      1.4.2 (<a href="http://java.sun.com/j2se/1.4.2/download.html">download</a>) 
      or 5.0 (<a href="http://java.sun.com/j2se/1.5.0/download.jsp">download</a>)</li>
  </ul>   
  
  <p>Also, you will use 4 icons in the tutorial. You can right-click
   them here and save them locally, then copy them to the module project's
   location, after you create the module project later in this tutorial. Here are
   the 4 icons:</p>
  
   <p><img alt="" src="../../images/tutorials/nodes-3/down-rectangle.png"/></p>
    <p><img alt="" src="../../images/tutorials/nodes-3/right-rectangle.png"/></p>
    <p><img alt="" src="../../images/tutorials/nodes-3/marilyn.gif"/></p>
   <p><img alt="" src="../../images/tutorials/nodes-3/marilyn_category.gif"/></p>

<h2><a name="gettingtoknowthesample"></a>Getting Started</h2>

<p>In this section, we use wizards to create a module project and
 a custom window component. We add a JScrollPane and create a new
  <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/BeanTreeView.html">BeanTreeView</a>. 
 We then install the module project and display
   our view's top node.</p>

<ol>

<li>Choose File &gt; New Project. In the New Project wizard,
 choose NetBeans Plug-in Modules under Categories and Module Project
 under Projects. Click Next. Type <tt>ExplorerBeanTreeView</tt> in Project Name
  and set Project Location to an appropriate folder on your disk. If they
 are not selected, select
   Standalone Module and Set as Main Project. Click Next.
  
   </li><li>Type <tt>org.netbeans.myfirstexplorer</tt> in Code Name Base
    and <tt>Explorer Bean Tree View</tt> in Module Display Name. Click Finish.

    
 </li><li>Right-click the project, choose Properties, click Libraries
in the Project Properties dialog box and declare a dependency on the following APIs:
 
<ul>
<li><a href="https://netbeans.org/download/dev/javadoc/org-openide-actions/overview-summary.html">Actions API</a>
</li><li><a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/overview-summary.html">Explorer and Property Sheet API</a>
</li><li><a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/overview-summary.html">Nodes API</a>
</li></ul></li>

    
<li>Right-click the module project, choose
 New &gt; File/Folder and choose Window Component from the
 NetBeans Module Development category. Click Next. Choose <tt>editor</tt>
 in the drop-down list and select Open on Application Start. Click Next.
 
</li><li>Type <tt>MyFirst</tt> in Class Name Prefix. Optionally,
 add an icon with a dimension of 16x16 pixels. Click Finish.

 
</li><li>Open <tt>MyFirstTopComponent.java</tt> in the Design view.
 Right-click in the TopComponent, choose Set Layout,
  and select BorderLayout. 

</li><li>Use the Palette (Ctrl-Shift-8) to drop a
 <tt>JScrollPane</tt> on <tt>MyFirstTopComponent.java</tt>. Resize the
 <tt>JScrollPane</tt> so that it covers the entire TopComponent. Right-click
  the <tt>JScrollPane</tt>, choose Change Variable Name and type <tt>moviePane</tt>. 
 
</li><li>Open the Inspector, if it isn't open. (Use the Window menu.)
 In the Inspector, select the <tt>moviePane</tt>, open the 
 Properties window (Ctrl-Shift-7), click the "Code" tab, and add this 
line to the Custom Creation Code property (the very last property in the list):

<pre class="examplecode">new <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/BeanTreeView.html">BeanTreeView()</a>;</pre>

<p>Click OK.</p>

<p>BeanTreeView is one of several views provided by the Explorer and Property Sheet API.
    We will look at the other views later in this tutorial.</p>
  
</li><li>Click the Source toggle button in the GUI Builder.
 Right-click in the Source Editor,
 and choose Fix imports. The dependency you set on "Explorer and Property Sheet API" will 
cause the import statement for the BeanTreeView being generated for you by the IDE.
 

</li><li>In the <tt>Bundle.properties</tt> file, change the <tt>CTL_MyFirstTopComponent</tt>
 key to the value "Marilyn Explorer". 


</li><li>Right-click the project node and choose "Install/Reload
 in Development IDE". If a warning message appears, click OK.
 When the module installs, look under the Window menu and you will find a new menu item
 called "Open MyFirst Window", at the top of the list of menu items. 
 Choose it and you will see the start of your explorer view:

 <p><img alt="" src="../../images/tutorials/nodes-3/marilyn-result.png"/></p>
 
 
<p>Without any coding, you have created the start of your BeanTreeView.</p>
    </li>
</ol>

<!-- ===================================================================================== -->
<h2><a name="gettingtoknowthesample"></a>Using Nodes to Represent Data</h2>

<p>Using nodes to represent data involves adding an Explorer Manager
 to our TopComponent's Lookup. The Explorer Manager controls the view, especially
  the top node of our view. Next we will create a Category object and a Movie object and display
   each via a separate <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode</a>
  object and Children.Keys object. The <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode</a> provides the
    basic implementation of a node, allowing you to provide icons, as well
     as actions such as Cut and Delete. With the Children.Keys object, you simplify
   the handling of the nodes, using lightweight keys instead of the nodes themselves.
   Further details on the specific approaches taken are explained where appropriate below.</p>

<div class="indent">
  <h3 class="tutorial"><a name="installing-sample"></a>Setting Up an Explorer Manager</h3>

<p>An <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/ExplorerManager.html">Explorer Manager</a>
 is the NetBeans API class that manages a view. For example, it notifies PropertyChangeListeners
  about changes to the nodes in the view. It also controls the root node
 in a view. For example, when you want to define a root node, you need
 to use the Explorer Manager's <tt>setRootContext()</tt> method.
 To provide an Explorer Manager in a TopComponent, you
 must implement <tt>ExplorerManager.Provider</tt>, as shown in this subsection.</p>
   
<ol>

 
<li>Open the <tt>MyFirstTopComponent.java</tt> in the
  Source view and add <tt>implements ExplorerManager.Provider</tt> 
 to the signature at the top of the class. 

</li><li>Next, instantiate the <tt><a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/ExplorerManager.html">ExplorerManager</a></tt> as a transient object:

<pre class="examplecode">private transient ExplorerManager explorerManager = new ExplorerManager();</pre>

</li><li>Place the cursor in the signature.
 A lightbulb will prompt you to let the IDE insert an import statement and implement the abstract methods. 
 Follow its advice, by clicking on the suggestion,
  and then fill out the generated <tt>getExplorerManager()</tt> as follows:

<pre class="examplecode">public ExplorerManager getExplorerManager() {
     return explorerManager;
}</pre>

</li><li>Now go to the Constructor and add the following after the last existing line:

<pre class="examplecode"><a href="https://netbeans.org/download/dev/javadoc/org-openide-windows/org/openide/windows/TopComponent.html#associateLookup(org.openide.util.Lookup)">associateLookup</a>(<a href="http://www.netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/ExplorerUtils.html">ExplorerUtils</a>.<a href="http://www.netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/ExplorerUtils.html#createLookup(org.openide.explorer.ExplorerManager,%20javax.swing.ActionMap)">createLookup(explorerManager, getActionMap())</a>);
explorerManager.setRootContext(new <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode(new CategoryChildren())</a>);
explorerManager.getRootContext().setDisplayName("Marilyn Monroe's Movies");</pre>

<p>Here we place the Explorer Manager in the TopComponent's Lookup.
 We set a class called "CategoryChildren" as the root node. We will create
  this class in the next section, and we will display it
  as the first node in our view. As display name it receives "Marilyn Monroe's Movies".</p>

</li><li>Fix imports. A red underline will remain because we have not created
    the CategoryChildren class yet. We will do so in the next section.</li>

</ol>
</div>

<div class="indent">
  <h3 class="tutorial"><a name="installing-sample"></a>Creating a Category</h3>

  <p>Let's first define what a "Category" is. </p>
<ol>
<li>Create a class
 called <tt>Category.java</tt> and add the following content:


<pre class="examplecode">public class Category {
    
    private String name;
    
    /** Creates a new instance of Category */
    public Category() {
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
}</pre>

 <p>From the above, you can see that a category has a name, and nothing more.</p>

 
</li><li>Create
another class, this time for creating the nodes for the categories:

<pre class="examplecode">public class CategoryChildren extends <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Children.Keys.html">Children.Keys</a> {
    
    private String[] Categories = new String[]{
        "Adventure",
        "Drama",
        "Comedy",
        "Romance",
        "Thriller"};
    
    public CategoryChildren() {
    }
    
     protected Node[] <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Children.Keys.html#createNodes%28java.lang.Object%29">createNodes(Object key)</a> {
        Category obj = (Category) key;
        return new Node[] { new CategoryNode( obj ) };
    }
    
    protected void <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Children.html#addNotify%28%29">addNotify()</a> {
        super.addNotify();
        Category[] objs = new Category[Categories.length];
        for (int i = 0; i < objs.length; i++) {
            Category cat = new Category();
            cat.setName(Categories[i]);
            objs[i] = cat;
        }
        setKeys(objs);
    }
    
}</pre>

<p>In this example, a popular children implementation called <tt>Children.Keys</tt> is used. 
 By subclassing <tt>Children.Keys</tt>, you need not explicitly keep track of the nodes. 
 Instead, you keep track of a set of keys, which are lighter 
 weight objects. Each key typically represents one node. You must tell the implementation how 
 to create a node for each key. You can decide for yourself what type of keys to use.</p>
 
<p><tt>addNotify()</tt> is called the first time that a list of nodes is needed. 
 An example of this is when a node is expanded. Here, when <tt>addNotify()</tt> is called, 
 a new category is instantiated. When a child node needs to be constructed,
 the <tt>createNodes()</tt> method is called. It is passed the key for which it is making a node. It returns either none, 
 one, or more nodes corresponding to what should be displayed for the key. 
In this example, a new instance of one category node is being created, and the
key is passed into its constructor.</p>

</li><li>Fix imports, choosing <tt>org.openide.nodes.Children</tt> and <tt>org.openide.nodes.Node</tt>.


<p>Note that in the code above, 
    we create a node called <tt>CategoryNode</tt>. We will create it in the next step.</p>

</li><li>Create a class called <tt>CategoryNode.java</tt>
 and define it as follows:


<pre class="examplecode">public class CategoryNode extends <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode</a> {
    
    /** Creates a new instance of CategoryNode */
    public CategoryNode( Category category ) {
        super( new MovieChildren(category), Lookups.singleton(category) );
        <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Node.html#setDisplayName(java.lang.String)">setDisplayName(category.getName())</a>;
        <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Node.html#setDisplayName(java.lang.String)">setIconBaseWithExtension("org/netbeans/myfirstexplorer/marilyn_category.gif")</a>;
    }
    
    public PasteType <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html#getDropType(java.awt.datatransfer.Transferable,%20int,%20int)">getDropType(Transferable t, final int action, int index)</a> {
        final Node dropNode = NodeTransfer.node( t, 
                DnDConstants.ACTION_COPY_OR_MOVE+NodeTransfer.CLIPBOARD_CUT );
        if( null != dropNode ) {
            final Movie movie = (Movie)dropNode.getLookup().lookup( Movie.class );
            if( null != movie  && !this.equals( dropNode.getParentNode() )) {
                return new PasteType() {
                    public Transferable paste() throws IOException {
                        getChildren().add( new Node[] { new MovieNode(movie) } );
                        if( (action & DnDConstants.ACTION_MOVE) != 0 ) {
                            dropNode.getParentNode().getChildren().remove( new Node[] {dropNode} );
                        }
                        return null;
                    }
                };
            }
        }
        return null;
    }
    
    public Cookie <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html#getCookie(java.lang.Class)">getCookie(Class clazz)</a> {
        Children ch = getChildren();
        
        if (clazz.isInstance(ch)) {
            return (Cookie) ch;
        }
        
        return super.getCookie(clazz);
    }
    
    protected void <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html#createPasteTypes(java.awt.datatransfer.Transferable,%20java.util.List)">createPasteTypes(Transferable t, List s)</a> {
        super.createPasteTypes(t, s);
        PasteType paste = getDropType( t, DnDConstants.ACTION_COPY, -1 );
        if( null != paste )
            s.add( paste );
    }
    
    public Action[] <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Node.html#getActions(boolean)">getActions(boolean context)</a> {
        return new Action[] {
            SystemAction.get( NewAction.class ),
            SystemAction.get( PasteAction.class ) };
    }
    
    public boolean <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html#canDestroy()">canDestroy()</a> {
        return true;
    }
    
}</pre>

<p>An AbstractNode is a basic implementation of a node. It simplifies common
 requirements, such as the creation of the display name and the handling of icons.
  Other common requirements are handled as well. To understand what each of the methods 
 in the code above does, 
 click the method's link to jump to the related Javadoc.</p>

</li><li>Fix imports. After you fic the import statements, several red underlines
 will remain, because we have not created <tt>Movie.java</tt>, <tt>MovieChildren.java</tt>,
 and <tt>MovieNode.java</tt>. yet. We will do so in the next section.</li>

</ol>
</div>
      
      <div class="indent">
  <h3 class="tutorial"><a name="installing-sample"></a>Creating a Movie</h3>


<p>Next, we'll work on adding the children belonging to the categories. 
    And the children are movies. Let's begin by defining what a "movie" is.</p>

 <ol>
<li>Create a
 class called <tt>Movie.java</tt>, with the following content:


<pre class="examplecode">public class Movie {
    
    private Integer number;
    private String category;
    private String title;
    
    /** Creates a new instance of Instrument */
    public Movie() {
    }
    
    public Integer getNumber() {
        return number;
    }
    
    public void setNumber(Integer number) {
        this.number = number;
    }
    
    public String getCategory() {
        return category;
    }
    
    public void setCategory(String category) {
        this.category = category;
    }
    
    public String getTitle() {
        return title;
    }
    
    public void setTitle(String title) {
        this.title = title;
    }
    
}</pre>

 <p>From the above, you can see that a movie has a number, belongs to a category, and has a title.</p>
 
</li><li>Now let's create the category's children. The
 class to be created is called <tt>MovieChildren.java</tt>. We use
   <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Index.ArrayChildren.html">Index.ArrayChildren</a>,
 so that we can put the nodes in an array list, which is loaded as needed. Until a 
 child node is needed, such as when the parent node is expanded, it is not created. This is the content of the class:

<pre class="examplecode">public class MovieChildren  extends <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Index.ArrayChildren.html">Index.ArrayChildren</a> {
    
    private Category category;
    
    private String[][] items = new String[][]{
        {"0", "Adventure", "River of No Return"},
        {"1", "Drama", "All About Eve"},
        {"2", "Drama", "Home Town Story"},
        {"3", "Comedy", "We're Not Married!"},
        {"4", "Comedy", "Love Happy"},
        {"5", "Romance", "Some Like It Hot"},
        {"6", "Romance", "Let's Make Love"},
        {"7", "Romance", "How to Marry a Millionaire"},
        {"8", "Thriller", "Don't Bother to Knock"},
        {"9", "Thriller", "Niagara"},
    };
    
    public MovieChildren(Category Category) {
        this.category = Category;
    }
    
    protected java.util.List&lt;Node&gt; <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Index.ArrayChildren.html#initCollection()">initCollection()</a> {
        ArrayList childrenNodes = new ArrayList( items.length );
        for( int i=0; i&lt;items.length; i++ ) {
            if( category.getName().equals( items[i][1] ) ) {
                Movie item = new Movie();
                item.setNumber(new Integer(items[i][0]));
                item.setCategory(items[i][1]);
                item.setTitle(items[i][2]);
                childrenNodes.add( new MovieNode( item ) );
            }
        }
        return childrenNodes;
    }
}</pre>

</li><li>Right-click the project, choose Properties, and use the Sources category
 to change the source level from 1.4 to 1.5. Click OK.

</li><li>Fix imports. A red underline will remain because we have
 not create <tt>MovieNode.java</tt>, which we will do in the next step.

</li><li>Create a class called <tt>MovieNode.java</tt>
 and define it as follows:

<pre class="examplecode">public class MovieNode extends <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode</a> {
    
    private Movie movie;
    
    /** Creates a new instance of InstrumentNode */
    public MovieNode(Movie key) {
        super(Children.LEAF, Lookups.fixed( new Object[] {key} ) );
        this.movie = key;
        <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Node.html#setDisplayName(java.lang.String)">setDisplayName(key.getTitle())</a>;
        <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html#setIconBaseWithExtension(java.lang.String)">setIconBaseWithExtension("org/netbeans/myfirstexplorer/marilyn.gif")</a>;
    }
    
    public boolean <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html#canCut()">canCut()</a> {
        
        return true;
    }
    
    public boolean <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html#canDestroy()">canDestroy()</a> {
        return true;
    }
    
    public Action[] <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/Node.html#getActions(boolean)">getActions(boolean popup)</a> {
        return new Action[] {
            SystemAction.get( CopyAction.class ),
            SystemAction.get( CutAction.class ),
            null,
            SystemAction.get( DeleteAction.class ) };
    }
    
}</pre>

 <p>Fix imports.</p>

<p>Notice that most of this class is about defining actions on 
 the movie nodes. When you right-click a movie, you'll be 
 able to choose "Copy" or "Cut" or "Delete". </p></li>
 </ol>
</div>

<div class="indent">
  <h3 class="tutorial"><a name="installing-sample"></a>Creating a Root Node</h3>

  <p>Now we are going to install our module. When we do so, we will test
   our module's functionality and see if everything is as we would want it to be.</p>
   
   <ol>
   <li>Right-click the module and choose Install/Reload in Development IDE.
   </li><li>Examine the result:
      
       <p><img alt="" src="../../images/tutorials/nodes-3/marilyn-result2.png"/></p>

</li><li>Notice that even though you can drag and drop movies from
 one category to another (by dragging with your mouse, with the Ctrl
 key held down when you want to copy a node), 
 the menu items are greyed out. Also, notice that
  the root node does not have an icon.

  </li><li>First, we need to enable the menu items by adding the actions
   to the TopComponent's action map. Do this by adding the following
    snippet to the end of the TopComponent's Constructor:
    
<pre class="examplecode">ActionMap map = getActionMap();
map.put(DefaultEditorKit.copyAction, ExplorerUtils.actionCopy(explorerManager));
map.put(DefaultEditorKit.cutAction, ExplorerUtils.actionCut(explorerManager));
map.put(DefaultEditorKit.pasteAction, ExplorerUtils.actionPaste(explorerManager));
map.put("delete", ExplorerUtils.actionDelete(explorerManager, true));</pre>

</li><li>Next, to be able to control the icon displayed by the root node,
 we need to create a class for that node. Currently, we are using a default
  <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode</a>, over which we have no control.
  
  <p>Create a class called <tt>RootNode.java</tt>, with this content:</p>
  
<pre class="examplecode">public class RootNode extends <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode</a> {
    
    /** Creates a new instance of RootNode */
    public RootNode(Children children) {
        super(children);
    }
    
    public Image getIcon(int type) {
        return Utilities.loadImage("org/netbeans/myfirstexplorer/right-rectangle.png");
    }
    
    public Image getOpenedIcon(int type) {
        return Utilities.loadImage("org/netbeans/myfirstexplorer/down-rectangle.png");
    }
    
}</pre>

<p>Notice that here we set one icon for when the node is in its closed state
 and another for when it is expanded. To use this node, we need to change this line
 in the TopComponent:</p>
  
<pre class="examplecode">explorerManager.setRootContext(new <a href="https://netbeans.org/download/dev/javadoc/org-openide-nodes/org/openide/nodes/AbstractNode.html">AbstractNode</a>(new CategoryChildren()));</pre>

<p>We need to replace that line with this line:</p>

<pre class="examplecode">explorerManager.setRootContext(new RootNode(new CategoryChildren()));</pre>

</li><li>Install the module again and notice the icons displayed for the root node's
   collapsed and expanded states. Here, the icon for the expanded state is shown:
   
   
<p><img alt="" src="../../images/tutorials/nodes-3/marilyn-result3.png"/></p>

<p>Also notice that the movie node's menu items are now enabled and functional.</p></li>
 
 </ol>
</div>


 <!-- ===================================================================================== -->
<h2><a name="gettingtoknowthesample"></a>Using Explorer Views to View Data</h2>

<p>The NetBeans APIs provide a variety of explorer views, which are very
 simple to add to your TopComponent. After adding one or two lines of code,
  the view on your data can be completely different, creating a radically
   altered display for your end users and a wide range of choices for you
 and your development team. </p>

<p>However, note that only the BeanTreeView supports
  the drag and drop functionality you added earlier in this tutorial. When you
   change to a different explorer view, as shown below, the drag and drop functionality
    will simply be disabled.</p>


      <div class="indent">

 
<h3 class="tutorial"><a name="installing-software"></a>List View</h3>

<p>List view is an explorer view that displays items in a list. It is provided by
 the <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/ListView.html">ListView</a>
  class, which belongs to the Explorer And Property Sheet API.</p>

<ol>

    <li>Add this line to the end of the TopComponent's Constructor:
    
<pre class="examplecode">listView = new ListView();</pre>
    
    <p>Put the cursor in the line and let the IDE generate
     an import statement for <tt>org.openide.explorer.view.ListView</tt>.
     Also let the IDE create the <tt>listView</tt> field.</p>
     
      </li><li>Below the line above, add this line, which adds the view to the TopComponent:
      
<pre class="examplecode">add(listView, BorderLayout.CENTER);</pre>
     
<p>Let the IDE generate the <tt>java.awt.BorderLayout</tt> import statement for BorderLayout.</p>

<p><b>Note:</b> When you created the TopComponent earlier in this tutorial,
 you should have set the layout manager to BorderLayout. If you did not do this,
 make the JScrollPane smaller, right-click the TopComponent, choose Set Layout,
  and select BorderLayout.</p>
  
 </li><li>Install the module again. Notice that the view is now as follows:
 
 <p><img alt="" src="../../images/tutorials/nodes-3/listview1.png"/></p>
 
 <p>When you click on a category, the movies are displayed:</p>
 
  <p><img alt="" src="../../images/tutorials/nodes-3/listview2.png"/></p></li>
  
  </ol>
</div>
      
       <div class="indent">

 
<h3 class="tutorial"><a name="installing-software"></a>Choice View</h3>

<p>Choice view is an explorer view based on a combo box. It is provided by
 the <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/ChoiceView.html">ChoiceView</a>
  class, which belongs to the Explorer And Property Sheet API.</p>

<ol>
    <li>Add this line to the end of the TopComponent's Constructor:
    
<pre class="examplecode">choiceView = new ChoiceView();</pre>
    
    <p>Put the cursor in the line and let the IDE generate
     an import statement for <tt>org.openide.explorer.view.ChoiceView</tt>.
      Also let the IDE create the <tt>choiceView</tt> field.</p>
     
      </li><li>Instead of the line that
 adds a ListView to the TopComponent, write a line that
 adds the ChoiceView:
      
<pre class="examplecode">add(choiceView, BorderLayout.CENTER);</pre>
     

 </li><li>Install the module again. Notice that the view is now as follows:
 
 <p><img alt="" src="../../images/tutorials/nodes-3/choiceview1.png"/></p>
 
  <p><b>Note:</b> If your TopComponent is very large, the combo box
   provided by the choice view will be very large as well.</p></li>
  
  </ol>
</div>
      
        <div class="indent">

 
<h3 class="tutorial"><a name="installing-software"></a>Menu View</h3>

<p>Menu view is an explorer view that displays the hierarchy
 of nodes in a popup menu. Initially, it shows a left button which 
 opens a popup menu from the root context and a right button which 
opens a popup menu from the currently explored context. It is provided by
 the <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/MenuView.html">MenuView</a>
  class, which belongs to the Explorer And Property Sheet API.</p>


<ol>
    <li>Add this line to the end of the TopComponent's Constructor:
    
<pre class="examplecode">menuView = new MenuView();</pre>
    
    <p>Put the cursor in the line and let the IDE generate
     an import statement for <tt>org.openide.explorer.view.MenuView</tt>.
      Also let the IDE create the <tt>menuView</tt> field.</p>
     
     </li><li>Instead of the line that
 adds a ChoiceView to the TopComponent, write a line that
 adds the MenuView:
      
<pre class="examplecode">add(menuView, BorderLayout.CENTER);</pre>
  
 </li><li>Install the module again. Notice that the view is now as follows:
 
 <p><img alt="" src="../../images/tutorials/nodes-3/menuview1.png"/></p>
 
 <p>When you click on the first button, the complete list of categories is displayed:</p>
 
  <p><img alt="" src="../../images/tutorials/nodes-3/menuview2.png"/></p>
  
  <p>When you click with the right mouse button on the "Browse from root" button,
   the "Browse from current point" button is enabled and you can browse
    to movies within the selected category:</p>
    
     <p><img alt="" src="../../images/tutorials/nodes-3/menuview3.png"/></p></li>
  
  
  </ol>
</div>
      
        <div class="indent">
      
      <h3 class="tutorial"><a name="installing-software"></a>Other Views</h3>

<p>The <tt><a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/package-summary.html">org.openide.explorer.view</a></tt> package provides many other
 explorer views, in addition to those outlined above. For example, <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/IconView.html">IconView</a>
  presents the categories and its contents as icons:</p>
  
   <p><img alt="" src="../../images/tutorials/nodes-3/iconview1.png"/></p>
   
   <p><img alt="" src="../../images/tutorials/nodes-3/iconview2.png"/></p>
   
   <p>Other views include <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/ContextTreeView.html">ContextTreeView</a> 
 and <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/ListTableView.html">ListTableView</a>.</p>
    
 <p>Finally, a <a href="https://netbeans.org/download/dev/javadoc/org-openide-explorer/org/openide/explorer/view/TreeTableView.html">TreeTableView</a>
  could also be used. This NetBeans API class lets you
 create a view tree of nodes on the left and its properties in a table on the right. This is
  an area that deserves a tutorial of its own. Similarly, creating you own explorer view is a
   worthwhile but complex project that will be described in a separate tutorial.</p>
    </div>
      
 <!-- ===================================================================================== -->
<h2><a name="gettingtoknowthesample"></a>Using Palette Items to Reuse Nodes</h2>

<p>Alternatively, the nodes can form the basis of palette items, as shown below:</p>

<p><img alt="" src="../../images/tutorials/nodes-3/comp-pal.png"/></p>

<p>In this section,
 you are shown how to add the items to a Component Palette and how to add some
  simple drag and drop functionality to the items in the palette. Only a brief
   overview will be given here, because other tutorials exist that provide
   details on the Component Palette API.</p>
   
   <p>Instead of adding an Explorer Manager to the TopComponent's Lookup,
 you will need to add a <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteController.html">PaletteController</a>.
  When you do this, the Component Palette opens when the TopComponent opens, displaying
 its content, consisting of palette items. <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteController.html">PaletteController</a>
  is provided by the Core - Component Palette API.</p>
   
<ol>
<li>Right-click the project, choose
  Properties, and add a dependency on Core - Component Palette in the Libraries category
   of the Project Properties dialog box.
   
</li><li>Declare a new <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteController.html">PaletteController</a>
  and set the root node as the palette's root:
   
<pre class="examplecode">private <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteController.html">PaletteController</a> palette = null;
private RootNode paletteRoot;</pre>
   
</li><li>In the TopComponent's Constructor, comment out the calls to the Explorer Manager.
    You can also comment out the definition of the action map, since the Component
     Palette automatically provides Copy, Cut, Paste, and Delete actions to palette items.
     
     <p>In the Inspector, select the <tt>moviePane</tt>, open the 
 Properties window (Ctrl-Shift-7), click the "Code" tab, and <i>delete</i> the 
line in the Custom Creation Code property (the very last property in the list).</p>
     
</li><li>At the end of the Constructor, add this line to add the Component
      Palette to the TopComponent's Lookup:
      
<pre class="examplecode">associateLookup( Lookups.fixed( new Object[] {getPalette()} ));</pre>

</li><li>Here, we create a new instance of the <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteController.html">PaletteController</a>
 and return it to the TopComponent's Lookup:
   
<pre class="examplecode">private <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteController.html">PaletteController</a> getPalette() {
    if( null == palette ) {
        paletteRoot = new RootNode(new CategoryChildren());
        paletteRoot.setName( "Palette Root");

        palette = <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteFactory.html">PaletteFactory</a>.createPalette( paletteRoot, 
                 new MyPaletteActions(), null, new MyDragAndDropHandler() );
    }
    return palette;
}</pre>

</li><li>A palette consists of a root, a set of actions,
 and a handler for drag and drop events. For purposes of this
  simple example, we will set our palette actions to null:

<pre class="examplecode">private static class MyPaletteActions extends <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/PaletteActions.html">PaletteActions</a> {
    public Action[] getImportActions() {
        return null;
    }

    public Action[] getCustomPaletteActions() {
        return null;
    }

    public Action[] getCustomCategoryActions(Lookup lookup) {
        return null;
    }

    public Action[] getCustomItemActions(Lookup lookup) {
        return null;
    }

    public Action getPreferredAction(Lookup lookup) {
        return null;
    }

}</pre>


</li><li>And here is the definition of our drag and drop handler, using
 the NetBeans API class <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/DragAndDropHandler.html">DragAndDropHandler</a>:

<pre class="examplecode">public static final DataFlavor MyCustomDataFlavor
      = new DataFlavor( Object.class, "MyDND" );
private static class MyDragAndDropHandler extends <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/DragAndDropHandler.html">DragAndDropHandler</a> {
    public void <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-spi-palette/org/netbeans/spi/palette/DragAndDropHandler.html#customize(org.openide.util.datatransfer.ExTransferable,%20org.openide.util.Lookup)">customize(ExTransferable exTransferable, Lookup lookup)</a> {
        final MovieNode item = (MovieNode)lookup.lookup( MovieNode.class );
        if( null != item ) {
            exTransferable.<a href="https://netbeans.org/download/dev/javadoc/org-openide-util/org/openide/util/datatransfer/ExTransferable.html#put(org.openide.util.datatransfer.ExTransferable.Single)">put</a>( new <a href="http://www.netbeans.org/download/dev/javadoc/org-openide-util/org/openide/util/datatransfer/ExTransferable.Single.html">ExTransferable.Single( MyCustomDataFlavor )</a> {
                protected Object <a href="https://netbeans.org/download/dev/javadoc/org-openide-util/org/openide/util/datatransfer/ExTransferable.Single.html#getData()">getData()</a> throws IOException, UnsupportedFlavorException {
                    //return item.getSomeData();
                    return null;
                }
            });
        }
    }
}</pre></li>

<li>Install the module again. When the TopComponent opens, the new
 Component Palette is shown. The categories you created in this tutorial
  are now categories in the Component Palette, while the movies are items
   within the categories. Next, you need to add drag and drop functionality
    to the items in the palette, as described in the <a href="https://platform.netbeans.org/tutorials/nbm-palette-api4.html">NetBeans Drag and Drop Tutorial</a>.
</li>
</ol>
  
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