sketchframe.java

JAVA 2入门经典 练习答案

  // Save the sketch if it is necessary
  private void saveOperation() {
    if(!sketchChanged)
      return;

    File file = modelFile;
    if(file == null) {
      file = showDialog("Save Sketch",
                        "Save",
                        "Save the sketch",
                        's',
                        new File(files.getCurrentDirectory(), filename));
      if(file == null || (file.exists() &&                      // Check for existence
        JOptionPane.NO_OPTION ==          // Overwrite warning
            JOptionPane.showConfirmDialog(SketchFrame.this,
                                          file.getName()+" exists. Overwrite?",
                                          "Confirm Save As",
                                          JOptionPane.YES_NO_OPTION,
                                          JOptionPane.WARNING_MESSAGE)))
                                          return;                            // No selected file
    }
    saveSketch(file);    
  }

  // Display a custom file save dialog
  private File showDialog(String dialogTitle,
                          String approveButtonText,
                          String approveButtonTooltip,
                          char approveButtonMnemonic,
                          File file) {                // Current file - if any

    files.setDialogTitle(dialogTitle);
    files.setApproveButtonText(approveButtonText);
    files.setApproveButtonToolTipText(approveButtonTooltip);
    files.setApproveButtonMnemonic(approveButtonMnemonic);
    files.setFileSelectionMode(files.FILES_ONLY);
    files.rescanCurrentDirectory();
    files.setSelectedFile(file);

    ExtensionFilter sketchFilter = new ExtensionFilter(".ske",
                                                    "Sketch files (*.ske)");
    files.addChoosableFileFilter(sketchFilter);            // Add the filter
    files.setFileFilter(sketchFilter);                     // and select it

    int result = files.showDialog(SketchFrame.this, null);  // Show the dialog
    return (result == files.APPROVE_OPTION) ? files.getSelectedFile() : null;
  }

  // Retrieve the pop-up menu
  public JPopupMenu getPopup() {  
    return popup;  
  }

  private JButton addToolBarButton(Action action) {
    JButton button = toolBar.add(action);              // Add toolbar button
    button.setBorder(BorderFactory.createRaisedBevelBorder());// Add button border
    return button;
  }

  // Method to save the current sketch as an XML document
  private void saveXMLSketch(File outFile) {
    FileOutputStream outputFile = null;      // Stores an output stream reference 
    try {
      outputFile = new FileOutputStream(outFile);    // Output stream for the file 
      FileChannel outChannel = outputFile.getChannel(); // Channel for file stream 
      writeXMLFile(theApp.getModel().createDocument(), outChannel);

    } catch(FileNotFoundException e) {
      e.printStackTrace(System.err);
      JOptionPane.showMessageDialog(SketchFrame.this,
                       "Sketch file " + outFile.getAbsolutePath() + " not found.",
                       "File Output Error",
                       JOptionPane.ERROR_MESSAGE);
      return;                           // Serious error - return
    }
  }

  // Method to write the XML file for the current sketch (helper for saveXMLSketch())
  private void writeXMLFile(org.w3c.dom.Document doc, FileChannel channel) {
    StringBuffer xmlDoc = new StringBuffer(
                                 "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"); 
    xmlDoc.append(NEWLINE).append(getDoctypeString(doc.getDoctype()));
    xmlDoc.append(getDocumentNode(doc.getDocumentElement(), ""));
 
    try {
      channel.write(ByteBuffer.wrap(xmlDoc.toString().getBytes("UTF-8")));

    } catch(UnsupportedEncodingException e) {
      System.out.println(e.getMessage());

    } catch(IOException e) {
      JOptionPane.showMessageDialog(SketchFrame.this,
                                          "Error writing XML to channel.",
                                              "File Output Error",
                                              JOptionPane.ERROR_MESSAGE);
      e.printStackTrace(System.err);
      return;
    }
  }

   private String getDoctypeString(org.w3c.dom.DocumentType doctype) {
      // Create the opening string for the DOCTYPE declaration with its name
      String str = doctype.getName();
      StringBuffer doctypeStr = new StringBuffer("<!DOCTYPE ").append(str);        

      // Check for a system ID
      if((str = doctype.getSystemId()) != null)
        doctypeStr.append(" SYSTEM ").append(QUOTE).append(str).append(QUOTE);

      // Check for a public ID
      if((str = doctype.getPublicId()) != null)
        doctypeStr.append(" PUBLIC ").append(QUOTE).append(str).append(QUOTE);

      // Check for an internal subset
      if((str = doctype.getInternalSubset()) != null)
        doctypeStr.append('[').append(str).append(']');           

      return doctypeStr.append(TAG_END).toString();  // Append '>' & return string
  }

  private String getDocumentNode(Node node, String indent) {
    StringBuffer nodeStr = new StringBuffer().append(NEWLINE).append(indent); 
    String nodeName = node.getNodeName();       // Get name of this node

    switch(node.getNodeType()) {
      case Node.ELEMENT_NODE:
      nodeStr.append(TAG_START);
      nodeStr.append(nodeName);
      if(node.hasAttributes()) {             // If the element has attributes...
        org.w3c.dom.NamedNodeMap attrs = node.getAttributes();   // ...get them 
        for(int i = 0 ; i<attrs.getLength() ; i++) {
          org.w3c.dom.Attr attribute = (org.w3c.dom.Attr)attrs.item(i);      
          // Append " name="value" to the element string
          nodeStr.append(' ').append(attribute.getName()).append('=')
                        .append(QUOTE).append(attribute.getValue()).append(QUOTE);
        }
      }
      if(!node.hasChildNodes()) {        // Check for no children for this element
        nodeStr.append(EMPTY_TAG_END);   // There are none-close as empty element
        return nodeStr.toString();       // and return the completed element

      } else {                             // It has children
        nodeStr.append(TAG_END);         // so close start-tag
        NodeList list = node.getChildNodes();       // Get the list of child nodes
        assert list.getLength()>0;                  // There must be at least one
 
       // Append child nodes and their children...
        for(int i = 0 ; i<list.getLength() ; i++)     
          nodeStr.append(getDocumentNode(list.item(i), indent+" "));     
      }
      nodeStr.append(NEWLINE).append(indent).append(END_TAG_START)
                                               .append(nodeName).append(TAG_END);
      break;    

      case Node.TEXT_NODE:
      nodeStr.append(replaceQuotes(((org.w3c.dom.Text)node).getData()));
      break;

      default:
      assert false;
    }
    return nodeStr.toString();
  }
 
  public String replaceQuotes(String str) {
    StringBuffer buf = new StringBuffer();
    for(int i = 0 ; i<str.length() ; i++)
      if(str.charAt(i)==QUOTE)
        buf.append(QUOTE_ENTITY);
      else
        buf.append(str.charAt(i));

    return buf.toString(); 
  }       

  // Uses a SAX parser to open an XML sketch file
  private void openXMLSketch(File xmlFile) {
    SAXParserFactory spf = SAXParserFactory.newInstance();
    SAXParser parser = null;
    spf.setNamespaceAware(true);
    spf.setValidating(true);
    try {
     parser = spf.newSAXParser();
    } catch(SAXException e) {
      e.printStackTrace(System.err);
      System.exit(1);    
    } catch(ParserConfigurationException e) {
      e.printStackTrace(System.err);
      System.exit(1);    
    }
    SAXElementHandler handler = new SAXElementHandler(); 
    try {
       parser.parse(xmlFile, handler);
    }  catch(IOException e) {
      e.printStackTrace(System.err);
    }
    catch(SAXException e) {
      e.printStackTrace(System.err);
    }
    checkForSave();
    filename = xmlFile.getName();            // Update the file name
    setTitle(frameTitle+xmlFile.getPath());  // Change the window title
    sketchChanged = false;                     // Status is unchanged
  }

  // Method to create a SketchModel object from an XML Document object
  private SketchModel createSketchModel(org.w3c.dom.Document doc) {
   SketchModel model = new SketchModel();                 // The new model object

   // Get the first child of the root node
   org.w3c.dom.Node node = doc.getDocumentElement().getFirstChild();

   // Starting with the first child, check out each child in turn
   while (node != null) {
    assert node instanceof org.w3c.dom.Element;          // Should all be Elements
 
    String name = ((org.w3c.dom.Element)node).getTagName();  // Get the name

    if(name.equals("line"))                               // Check for a line
      model.add(new Element.Line((org.w3c.dom.Element)node)); 

    else if(name.equals("rectangle"))                     // Check for a rectangle
      model.add(new Element.Rectangle((org.w3c.dom.Element)node));  

    else if(name.equals("circle"))                        // Check for a circle
 

      model.add(new Element.Circle((org.w3c.dom.Element)node));     

    else if(name.equals("curve"))                         // Check for a curve
      model.add(new Element.Curve((org.w3c.dom.Element)node));      

    else if(name.equals("text"))                          // Check for a text
      model.add(new Element.Text((org.w3c.dom.Element)node));   

    node = node.getNextSibling();                          // Next child node
   }
      return model;    
  }

  // Defines a handler for SAX events when parsing an XML sketch
  /*
    At the start of a document we create an empty model. Data for Sketcher elements
    is recorded in the startElement() callback method and the element is ultimately
    created in the endElement() callback and added to the model. The model is inserted
    into the Sketcher application in the endDocument() callback method.
  */
  class SAXElementHandler extends DefaultHandler {
    public void startDocument() {
      xmlSketch = new SketchModel();                // Create the new model
    }    
    public void endDocument()  {
      theApp.insertModel(xmlSketch);                // Insert the new model
    }
  
    // This method will recognize an XML element and save any attributes it has
    // in a form to be used when the sketch element is created in the endElement() method
    public void startElement(String uri, String localName, String qname, 
                                                               Attributes attr) {
      // Determine what kind of element we have by comparing localName
      // with known element names.
      if(localName.equals("line")) {
        // Should be one attribute - the angle
        angle = Double.parseDouble(attr.getValue("angle"));
        elementType = LINE;

      } else if(localName.equals("position")) {
        position = getPoint(attr, localName);

      } else if(localName.equals("endpoint")) {
        endPoint = getPoint(attr,localName);