draganddropcontroller.java

java2高级教程大学教程的配套光盘源码

// DragAndDropController.java
// DragAndDropController is a controller for handling drag and
// drop in DeitelDrawing. DragAndDropController implements
// DragGestureListener and DragSourceListener to handle drag
// events and DropTargetListener to handle drop events.
package com.deitel.advjhtp1.drawing.controller;

// Java core packages
import java.util.*;
import java.io.*;
import java.awt.Point;
import java.awt.dnd.*;
import java.awt.datatransfer.*;

// Deitel packages
import com.deitel.advjhtp1.drawing.model.*;
import com.deitel.advjhtp1.drawing.model.shapes.*;

public class DragAndDropController implements DragGestureListener, 
   DragSourceListener, DropTargetListener {
     
   // model to control
   private DrawingModel drawingModel;  
   
   private boolean dragMode = false;  
  
   // DragAndDropController constructor
   public DragAndDropController( DrawingModel model )
   {
      drawingModel = model;
   }
   
   // set drag mode
   public void setDragMode( boolean drag )
   {
      dragMode = drag;
   }

   // recognize drag operation beginning (method of interface
   // DragGestureListener)
   public void dragGestureRecognized( DragGestureEvent event ) 
   {
      // if not in dragMode, ignore drag gesture
      if ( !dragMode ) 
         return; 

      // get Point at which drag began
      Point origin = event.getDragOrigin();
      
      // get MyShapes from DrawingModel
      List shapes = new ArrayList( drawingModel.getShapes() );

      // find top-most shape that contains drag origin (i.e.,
      // start at end of ListIterator and work backwards)
      ListIterator shapeIterator = 
         shapes.listIterator( shapes.size() );
      
      while ( shapeIterator.hasPrevious() ) {
         
         MyShape shape = ( MyShape ) shapeIterator.previous();

         if ( shape.contains( origin ) ) {
            
            // create TransferableShape for dragging shape
            // from Point origin
            TransferableShape transfer = 
               new TransferableShape( shape, origin );   

            // start drag operation
            event.startDrag( null, transfer, this );      
            
            break;
         }
         
      } // end while
      
   } // end method dragGestureRecognized

   // handle drop events (method of interface DropTargetListener)
   public void drop( DropTargetDropEvent event )
   {
      // get dropped object
      Transferable transferable = event.getTransferable();

      // get dropped object's DataFlavors
      DataFlavor[] dataFlavors = 
         transferable.getTransferDataFlavors();
      
      // get DropTargetDropEvent location
      Point location = event.getLocation();

      // process drops for supported types
      for ( int i = 0; i < dataFlavors.length; i++ ) {
         DataFlavor dataFlavor = dataFlavors[ i ];
            
         // handle drop of JPEG images
         if ( dataFlavor.equals( 
            DataFlavor.javaFileListFlavor ) ) {
               
            // accept the drop operation
            event.acceptDrop( DnDConstants.ACTION_COPY );
            
            // attempt to drop the images and indicate whether
            // drop is complete
            event.dropComplete( 
               dropImages( transferable, location ) );
         }

         // handle drop of TransferableShape objects
         else if ( dataFlavor.isMimeTypeEqual( 
            TransferableShape.MIME_TYPE ) ) {

            // accept drop of TransferableShape
            event.acceptDrop( DnDConstants.ACTION_MOVE );
            
            // drop TransferableShape into drawing
            dropShape( transferable, location );
            
            // complete drop operation
            event.dropComplete( true );
         }

         // reject all other DataFlavors
         else
            event.rejectDrop();   
         
      } // end for
      
   } // end method drop
   
   // drop JPEG images onto drawing
   private boolean dropImages( Transferable transferable,
      Point location )
   {
      // boolean indicating successful drop
      boolean success = true;
      
      // attempt to drop images onto drawing
      try {
         
         // get list of dropped files
         List fileList = 
            ( List ) transferable.getTransferData( 
               DataFlavor.javaFileListFlavor );
      
         Iterator iterator = fileList.iterator();

         // search for JPEG images
         for ( int i = 1; iterator.hasNext(); i++ ) {
            File file = ( File ) iterator.next();

            // if dropped file is a JPEG image, decode and
            // add MyImage to drawingModel
            if ( fileIsJPEG( file ) ) {
               
               // create MyImage for given JPEG file
               MyImage image = new MyImage();
               image.setFileName( file.getPath() );
               image.setPoint1( location.x, location.y );

               // add to DrawingModel
               drawingModel.addShape( image );
            }
            
            else 
               success = false;
            
         } // end for
         
      } // end try
      
      // handle exception if DataFlavor not supported
      catch ( UnsupportedFlavorException flavorException ) {
         success = false;
         flavorException.printStackTrace();
      }
      
      // handle exception reading File
      catch ( IOException ioException ) {
         success = false;
         ioException.printStackTrace();
      }
      
      return success;   
      
   } // end method dropImages
      
   // return true if File has .jpg or .jpeg extension
   private boolean fileIsJPEG( File file )
   {
      String fileName = file.getName().toLowerCase();
      
      return fileName.endsWith( ".jpg" ) ||
         fileName.endsWith( ".jpeg" );
   }
   
   // drop MyShape object onto drawing
   private void dropShape( Transferable transferable, 
      Point location )
   {
      try {
         
         DataFlavor flavor = new DataFlavor( 
            TransferableShape.MIME_TYPE, "Shape" );
         
         // get TransferableShape object
         TransferableShape transferableShape = 
            ( TransferableShape ) transferable.getTransferData( 
               flavor );
         
         // get MyShape and origin Point from TransferableShape
         MyShape shape = transferableShape.getShape();         
         Point origin = transferableShape.getOrigin();
     
         // calculate offset for dropping MyShape
         int xOffSet = location.x - origin.x;
         int yOffSet = location.y - origin.y;
         
         shape.moveByOffSet( xOffSet, yOffSet );
         
         // add MyShape to target DrawingModel
         drawingModel.addShape( shape );   
         
      } // end try
      
      // handle exception if DataFlavor not supported
      catch ( UnsupportedFlavorException flavorException ) {
         flavorException.printStackTrace();
      }

      // handle exception getting Transferable data
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }       
      
   } // end method dropShape
   
   // check for success when drag-and-drop operation ends
   // (method of interface DragSourceListener)
   public void dragDropEnd( DragSourceDropEvent event ) 
   {
      // if drop successful, remove MyShape from source 
      // DrawingModel
      if ( event.getDropSuccess() ) {
         
         // get Transferable object from DragSourceContext
         Transferable transferable = 
            event.getDragSourceContext().getTransferable();
         
         // get TransferableShape object from Transferable
         try {
            
            // get TransferableShape object
            TransferableShape transferableShape = 
               ( TransferableShape ) transferable.getTransferData( 
                  new DataFlavor( TransferableShape.MIME_TYPE, 
                     "Shape" ) );

            // get MyShape from TransferableShape object
            // and remove from source DrawingModel
            drawingModel.removeShape( 
               transferableShape.getShape() );
         }
         
         // handle exception if DataFlavor not supported
         catch ( UnsupportedFlavorException flavorException ) {
            flavorException.printStackTrace();
         }
         
         // handle exception getting transfer data
         catch ( IOException ioException ) {
            ioException.printStackTrace();
         }
         
      } // end if 
         
   } // end method dragDropEnd

   // required methods of interface DropTargetListener
   public void dragEnter( DropTargetDragEvent event ) {}
   public void dragExit( DropTargetEvent event ) {}
   public void dragOver( DropTargetDragEvent event ) {}
   public void dropActionChanged( DropTargetDragEvent event ) {}
   
   // required methods of interface DragSourceListener
   public void dragEnter( DragSourceDragEvent event ) {}
   public void dragExit( DragSourceEvent event ) {}   
   public void dragOver( DragSourceDragEvent event ) {}  
   public void dropActionChanged( DragSourceDragEvent event ) {}   
}

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 * (C) Copyright 2002 by Deitel & Associates, Inc. and         *
 * Prentice Hall. All Rights Reserved.                         *
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 * the theories and programs to determine their effectiveness. *
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