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接下来一步是创建一个叫 buildWelcomeTree()的方法。这个方法一次构建一个DefaultTreeModel变量，而不是通过分析一个现有的XML文字字符串。如果用户没有指定 XML文件就启动这个应用程序，将显示 DefaultTreeModel。见代码段1
代码段1：
private DefaultTreeModel buildWelcomeTree()
{
DefaultMutableTreeNode root;
DefaultMutableTreeNode instructions, openingDoc,
editingDoc, savingDoc;
DefaultMutableTreeNode openingDocText, editingDocText,
savingDocText;
DefaultMutableTreeNode development, addingFeatures,
contactingKyle;
root = new DefaultMutableTreeNode( "Welcome to XML View 1.0" );
instructions = new DefaultMutableTreeNode( "Instructions" );
openingDoc = new DefaultMutableTreeNode
( "Opening XML Documents" );
openingDocText = new DefaultMutableTreeNode
( "When invoking the XmlEditor from
the command-line, you must specify the filename." );
editingDoc = new DefaultMutableTreeNode
( "Editing an XML Document" );
editingDocText = new DefaultMutableTreeNode
( "XML text in the right hand frame
can be edited directly.
The \"refresh\" button will rebuild
the JTree in the left frame." );
savingDoc = new DefaultMutableTreeNode
( "Saving an XML Document" );
savingDocText = new DefaultMutableTreeNode
( "This iteration of the XmlEditor does
not provide the ability to save your
document. That will come with the
next article." );
root.add( instructions );
instructions.add( openingDoc );
instructions.add( editingDoc );
openingDoc.add( openingDocText );
editingDoc.add( editingDocText );
return new DefaultTreeModel( root );
} |
接下来的我们需要添加一个新的构造程序来简化默认显示功能，我们将修改主构造程序，这样它就不能接受任何参数，创建一个新的能接收单一的 XML文本字符串的构造程序。这样以来，如果没有 XML文本被显示的话就会创建默认 XTree对象，而如果 XML文本被显示的话将创建一个唯一的 XTree对象。代码段2中给出了两个构造程序。
代码段2：
public XTree( String text ) throws ParserConfigurationException
{
this();
refresh( text );
}
public XTree() throws ParserConfigurationException
{
super();
getSelectionModel().setSelectionMode(
TreeSelectionModel.SINGLE_TREE_SELECTION );
setShowsRootHandles( true );
setEditable( false );
dbf = DocumentBuilderFactory.newInstance();
dbf.setValidating( false );
db = dbf.newDocumentBuilder();
setModel( buildWelcomeTree() );
} |
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