ColorSink.java Source code

Introduction

Here is the source code for ColorSink.java

Source

/*
 * This example is from the book "Java Foundation Classes in a Nutshell".
 * Written by David Flanagan. Copyright (c) 1999 by O'Reilly & Associates.  
 * You may distribute this source code for non-commercial purposes only.
 * You may study, modify, and use this example for any purpose, as long as
 * this notice is retained.  Note that this example is provided "as is",
 * WITHOUT WARRANTY of any kind either expressed or implied.
 */

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import javax.swing.*;
import javax.swing.border.*;
import java.io.*;
import java.util.List;

/** 
 * This simple JTextArea subclass allows TransferableColor objects to
 * be pasted or dropped into it.  It also supports the pasting of
 * text, and the dropping of File objects.  
 */
public class ColorSink extends JTextArea implements DropTargetListener {
    /** Create a new ColorSink object */
    public ColorSink() {
        // Listen for double clicks.  Use them to trigger a paste action.
        addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent e) {
                if (e.getClickCount() == 2) {
                    pastecolor();
                    e.consume();
                }
            }
        });

        // We have to create a DropTarget object to support Drag-and-Drop
        // It will listen for drops on top of us, and notify our DropTargetListener
        // methods when drag-and-drop related events occur.
        setDropTarget(new DropTarget(this, this));
    }

    // This method is invoked when the user double-clicks on us.  It attempts
    // to paste a color or text.  Note that the JTextArea we extend
    // already supports cut-and-paste of text through the Ctrl-V keystroke.
    // This adds a different kind of cut-and-paste for demonstration purposes.
    public void pastecolor() {
        // Get the clipboard, and read its contents
        Clipboard c = this.getToolkit().getSystemClipboard();
        Transferable t = c.getContents(this);
        if (t == null) { // If nothing to paste
            this.getToolkit().beep(); // then beep and do nothing
            return;
        }
        try {
            // If the clipboard contained a color, use it as the background color
            if (t.isDataFlavorSupported(TransferableColor.colorFlavor)) {
                Color color = (Color) t.getTransferData(TransferableColor.colorFlavor);
                this.setBackground(color);
            }
            // If the clipboard contained text, insert it.
            else if (t.isDataFlavorSupported(DataFlavor.stringFlavor)) {
                String s = (String) t.getTransferData(DataFlavor.stringFlavor);
                this.replaceSelection(s);
            }
            // Otherwise, we don't know how to paste the data, so just beep.
            else
                this.getToolkit().beep();
        } catch (UnsupportedFlavorException ex) {
            this.getToolkit().beep();
        } catch (IOException ex) {
            this.getToolkit().beep();
        }
    }

    // The methods below are the methods of DropTargetListener.
    // They are invoked at various times when something is being
    // dragged over us, and allow us an opportunity to respond to the drag

    // This is the border we display when the user is dragging over us.
    protected static Border dropBorder = new BevelBorder(BevelBorder.LOWERED);

    // Something is being dragged over us.  If we can support this data type
    // tell the drag-and-drop system that we are interested, and display
    // a special border to tell the user that we're intereted.
    public void dragEnter(DropTargetDragEvent e) {
        if (e.isDataFlavorSupported(TransferableColor.colorFlavor)
                || e.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
            e.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
            this.setBorder(dropBorder);
        }
    }

    /** The user is no longer dragging over us, so restore the default border */
    public void dragExit(DropTargetEvent e) {
        this.setBorder(null);
    }

    /** This method is invoked when the user drops something on us */
    public void drop(DropTargetDropEvent e) {
        this.setBorder(null); // Restore the default border
        Transferable t = e.getTransferable(); // Get the data that was dropped

        // Check for types of data that we support
        if (t.isDataFlavorSupported(TransferableColor.colorFlavor)) {
            // If it was a color, accept it, and use it as the background color
            e.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
            try {
                Color c = (Color) t.getTransferData(TransferableColor.colorFlavor);
                this.setBackground(c);
                e.dropComplete(true);
            } catch (Exception ex) {
                e.dropComplete(false);
            }
        } else if (t.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
            // If it was a file list, accept it, read the first file in the list
            // and display the file contents
            e.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
            try {
                List files = (List) t.getTransferData(DataFlavor.javaFileListFlavor);
                File f = (File) files.get(0);
                BufferedReader in = new BufferedReader(new FileReader(f));
                String s;
                this.setText("");
                while ((s = in.readLine()) != null)
                    this.append(s);
                e.dropComplete(true);
            } catch (Exception ex) {
                e.dropComplete(false);
            }
        } else { // If it wasn't a color or a file list, reject it.
            e.rejectDrop();
            return;
        }
    }

    // These are unused DropTargetListener methods
    public void dragOver(DropTargetDragEvent e) {
    }

    public void dropActionChanged(DropTargetDragEvent e) {
    }

    /** This is a simple test program for ColorSource and ColorSink */
    public static void main(String[] args) {
        // Create a window
        JFrame f = new JFrame("ColorSourceTest");
        f.getContentPane().setLayout(new BorderLayout());

        // Add some ColorSources
        JPanel panel = new JPanel();
        f.getContentPane().add(panel, BorderLayout.NORTH);
        panel.add(new ColorSource(Color.yellow));
        panel.add(new ColorSource(Color.pink));
        panel.add(new ColorSource(Color.white));
        panel.add(new ColorSource(Color.gray));

        // Add a ColorSink
        ColorSink sink = new ColorSink();
        f.getContentPane().add(sink, BorderLayout.CENTER);

        // Pop it all up
        f.setSize(400, 300);
        f.show();
    }
}