listen to clipboard changes, check ownership?

Question

I want to be notified if a string is copied to the system clipboard. When a new string is copied from the same source application, the FlavorListener won\'t get an event. To

Answer 1

I think this would work :)

import java.awt.AWTEvent;
import java.awt.EventQueue;
import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.ClipboardOwner;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.event.ActionEvent;
import java.awt.event.InputEvent;
import java.io.IOException;
import java.util.Observable;
import java.util.Observer;

import javax.swing.JFrame;

public final class ClipboardMonitor extends Observable implements ClipboardOwner {
  private static ClipboardMonitor monitor = null;

  public ClipboardMonitor() {
        gainOwnership();
  }

  private void gainOwnership() {
        Clipboard clip = Toolkit.getDefaultToolkit().getSystemClipboard();
        try {
              Transferable content = clip.getContents(null);
              DataFlavor[] f = content.getTransferDataFlavors();
              boolean imageDetected = false;
              for (int i = 0; i < f.length; i++) {
                    //                        System.out.println("Name: " + f[i].getHumanPresentableName());
                    //                        System.out.println("MimeType: " + f[i].getMimeType());
                    //                        System.out.println("PrimaryType: " + f[i].getPrimaryType());
                    //                        System.out.println("SubType: " + f[i].getSubType());
                    if (f[i].equals(DataFlavor.imageFlavor)) {
                          imageDetected = true;
                          break;
                    }
              }
              if (imageDetected) {
                    System.out.println("Image content detected");
                    Transferable t = new Transferable() {
                          public DataFlavor[] getTransferDataFlavors() {
                                return new DataFlavor[] { DataFlavor.stringFlavor };
                          }
                          public boolean isDataFlavorSupported(DataFlavor flavor) {
                                return false;
                          }
                          public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
                                return "dummy text instead of snapshot image";
                          }
                    };
                    clip.setContents(t, this);
              } else {
                    clip.setContents(content, this);
              }
              setChanged();
              notifyObservers(content);
        } catch (IllegalArgumentException istateexception) {
              istateexception.printStackTrace();
        } catch (Exception ioexception) {
              ioexception.printStackTrace();
        }
  }

  private int getCurrentEventModifiers() {
        int modifiers = 0;
        AWTEvent currentEvent = EventQueue.getCurrentEvent();
        if (currentEvent instanceof InputEvent) {
              modifiers = ((InputEvent) currentEvent).getModifiers();
        } else
              if (currentEvent instanceof ActionEvent) {
                    modifiers = ((ActionEvent) currentEvent).getModifiers();
              }
        return modifiers;
  }

  public void lostOwnership(Clipboard clipboard, Transferable contents) {
        System.out.println("Ownership lost ...");
        new Thread(new Runnable() {
              public void run() {
                    try {
                          Thread.sleep(200);
                          gainOwnership();
                    } catch (Exception e) {
                          e.printStackTrace();
                    }
              }
        }).start();
  }

  public void flushClipboard() {
        Toolkit.getDefaultToolkit().getSystemClipboard().setContents(new StringSelection(""), null);
  }

  public static final ClipboardMonitor getMonitor() {
        if (monitor == null)
              monitor = new ClipboardMonitor();
        return (monitor);
  }

  public static void main(String[] args) {
        JFrame f = new JFrame();
        ClipboardMonitor monitor = ClipboardMonitor.getMonitor();
        monitor.addObserver(new Observer() {
              public void update(Observable o, Object arg) {
                    System.out.println("Clipboard has been regained!");
              }
        });

        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(500, 100);
        f.setVisible(true);
  }

}