imageselection.java

The Definitive Guide to Java Swing, Third Edition by John Zukowski (Author) 源码

import java.awt.*;
import java.awt.image.*;
import java.awt.datatransfer.*;
import java.io.*;
import javax.swing.*;

public class ImageSelection extends TransferHandler
    implements Transferable {

  private static final DataFlavor flavors[] = {DataFlavor.imageFlavor};

  private Image image;

  public int getSourceActions(JComponent c) {
    return TransferHandler.COPY;
  }

  public boolean canImport(JComponent comp, DataFlavor flavor[]) {
    if (!(comp instanceof JLabel) && !(comp instanceof AbstractButton)) {
      return false;
    }
    for (int i=0, n=flavor.length; i<n; i++) {
      for (int j=0, m=flavors.length; j<m; j++) {
        if (flavor[i].equals(flavors[j])) {
          return true;
        }
      }
    }
    return false;
  }

  public Transferable createTransferable(JComponent comp) {
    // Clear
    image = null;

    if (comp instanceof JLabel) {
      JLabel label = (JLabel)comp;
      Icon icon = label.getIcon();
      if (icon instanceof ImageIcon) {
        image = ((ImageIcon)icon).getImage();
        return this;
      }
    } else if (comp instanceof AbstractButton) {
      AbstractButton button = (AbstractButton)comp;
      Icon icon = button.getIcon();
      if (icon instanceof ImageIcon) {
        image = ((ImageIcon)icon).getImage();
        return this;
      }
    }
    return null;
  }

  public boolean importData(JComponent comp, Transferable t) {
    if (comp instanceof JLabel) {
      JLabel label = (JLabel)comp;
      if (t.isDataFlavorSupported(flavors[0])) {
        try {
          image = (Image)t.getTransferData(flavors[0]);
          ImageIcon icon = new ImageIcon(image);
          label.setIcon(icon);
          return true;
        } catch (UnsupportedFlavorException ignored) {
        } catch (IOException ignored) {
        }
      }
    } else if (comp instanceof AbstractButton) {
      AbstractButton button = (AbstractButton)comp;
      if (t.isDataFlavorSupported(flavors[0])) {
        try {
          image = (Image)t.getTransferData(flavors[0]);
          ImageIcon icon = new ImageIcon(image);
          button.setIcon(icon);
          return true;
        } catch (UnsupportedFlavorException ignored) {
        } catch (IOException ignored) {
        }
      }
    }
    return false;
  }

  // Transferable
  public Object getTransferData(DataFlavor flavor) {
    if (isDataFlavorSupported(flavor)) {
      return image;
    }
    return null;
  }

  public DataFlavor[] getTransferDataFlavors() {
    return flavors;
  }

  public boolean isDataFlavorSupported(DataFlavor flavor) {
    return flavors[0].equals(flavor);
  }
}