texttransferhandler.java

java tutorial.sun公司官方出品。java入门书籍。最新版

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 *     from this software without specific prior written permission.
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 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 */ 

package dnd;

/**
 * TextTransferHandler.java is used by the TextCutPaste.java example.
 */

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import javax.swing.*;
import javax.swing.text.*;

/**
 * An implementation of TransferHandler that adds support for the
 * import and export of text using drag and drop and cut/copy/paste.
 */
class TextTransferHandler extends TransferHandler {
    //Start and end position in the source text.
    //We need this information when performing a MOVE
    //in order to remove the dragged text from the source.
    Position p0 = null, p1 = null;

    /**
     * Perform the actual import.  This method supports both drag and
     * drop and cut/copy/paste.
     */
    public boolean importData(TransferHandler.TransferSupport support) {
        //If we can't handle the import, bail now.
        if (!canImport(support)) {
            return false;
        }

        //Fetch the data -- bail if this fails
        String data;
        try {
            data = (String)support.getTransferable().getTransferData(DataFlavor.stringFlavor);
        } catch (UnsupportedFlavorException e) {
            return false;
        } catch (java.io.IOException e) {
            return false;
        }

        JTextField tc = (JTextField)support.getComponent();      
        tc.replaceSelection(data);
        return true;
    }
    
    /**
     * Bundle up the data for export.
     */
    protected Transferable createTransferable(JComponent c) {
        JTextField source = (JTextField)c;
        int start = source.getSelectionStart();
        int end = source.getSelectionEnd();
        Document doc = source.getDocument();
        if (start == end) {
            return null;
        }
        try {
            p0 = doc.createPosition(start);
            p1 = doc.createPosition(end);
        } catch (BadLocationException e) {
            System.out.println(
                    "Can't create position - unable to remove text from source.");
        }
        String data = source.getSelectedText();
        return new StringSelection(data);
    }

    /**
     * These text fields handle both copy and move actions.
     */
    public int getSourceActions(JComponent c) {
        return COPY_OR_MOVE;
    }

    /**
     * When the export is complete, remove the old text if the action
     * was a move.
     */
    protected void exportDone(JComponent c, Transferable data, int action) {
        if (action != MOVE) {
            return;
        }
        
        if ((p0 != null) && (p1 != null) &&
            (p0.getOffset() != p1.getOffset())) {
            try {
                JTextComponent tc = (JTextComponent)c;
                tc.getDocument().remove(p0.getOffset(), 
                        p1.getOffset() - p0.getOffset());
            } catch (BadLocationException e) {
                System.out.println("Can't remove text from source.");
            }
        }
    }

    /**
     * We only support importing strings.
     */
    public boolean canImport(TransferHandler.TransferSupport support) {
        // we only import Strings
        if (!support.isDataFlavorSupported(DataFlavor.stringFlavor)) {
            return false;
        }
        return true;
    }
}