orig synopsis:
"System clipboard not Xlated to DataFlavor until a Java window gets input focus"


Name: diC59631 Date: 10/09/97


Test file included. This was run with JDK1.1.4 under Solaris 2.4. The window manager is fvwm, if that's relevant.
The test app reads the system clipboard contents every 3 seconds and displays
the string to screen.

Problem is that contents are not always made available in
AWT DataFlavors. If the clipboard is set by another process, the
contents are not available until the app window gets
user focus.

Here are the steps:

Start the program
.../jdk1.1.4/bin/java TestClipboard

Press the "Set Clipboard" button once

Observe that the window displays the text:
"Clipboard contents set"

Move the mouse cursor out of the window. Do not move
the mouse over the window for the remainder of this
test, until the instructions say to.

Put some other text in the System clipboard.
(E.g., highlight some text in Netscape Nav. and select
   Edit->Copy from the menu).

Observe that the window displays the copied text.

Without moving the mouse over the window, put a
different text string in the system clipboard again.
(E.g., highlight some text in Netscape Nav. and select
   Edit->Copy from the menu).

The text will not be displayed in the application window.
The error message in the app window is:
"Unable to obtain clipboard contents"

The error message printed to System.out is:
  java.io.IOException: could not get transfer data
  Couldn't get clipboard contents in format: Unicode String
  Clipboard content: sun.awt.motif.X11Selection@1dc60c20

Wait a bit and then move the mouse over the app window.
The clipboard contents will then be displayed by the app.

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;



public class TestClipboard extends Panel implements Runnable {
  private static ClipboardOwner clipOwner = new ClipboardObserver();
  Canvas contentDisplay = null;

  public TestClipboard () {
    setLayout(new BorderLayout());
    Panel bp = new Panel();
    bp.setLayout(new FlowLayout());
    Button setClip = (Button)bp.add(new Button("Set Clipboard"));
    setClip.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent ae) {
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
StringSelection contents =
new StringSelection("Clipboard contents set");
clipboard.setContents(contents, clipOwner);
      }
    });

    add("North", bp);

    contentDisplay = new ConentCanvas();
    add("Center", contentDisplay);

    Thread life = new Thread(this);
    life.start();
  }

  
  public void run() {
    while (true) {
      contentDisplay.repaint();
      try {
Thread.sleep(3000);
      } catch (InterruptedException ie) {
// ignore it
      }
    }
  }




  public static void main(String [] args) {
    Frame f = new Frame("Clipboard Test");
    TestClipboard tc = new TestClipboard();
    f.setLayout(new BorderLayout());
    f.add("Center", tc);
    f.pack();
    f.show();
  }
}


class ConentCanvas extends Canvas {

  public void paint(Graphics g) {
    String contentString = getContents();
    g.setColor(Color.black);
    g.drawString(contentString, 10, 30);
  }

  protected String getContents() {
    Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
    Transferable content = clipboard.getContents(this);
    System.out.println("content="+content);

    if (content != null) {
      try {
String dstData = (String)(content.getTransferData(DataFlavor.stringFlavor));
return dstData;
      } catch (Exception e) {
System.err.println(e);
System.err.println("Couldn't get clipboard contents in format: "+
DataFlavor.stringFlavor.getHumanPresentableName()); System.err.println("Clipboard content: "+content);
      }
    }
    return "Unable to obtain clipboard contents";
  }

  public Dimension getPreferredSize() {
    return new Dimension(300, 100);
  }
}


class ClipboardObserver implements ClipboardOwner {
  
  public void lostOwnership(Clipboard clipboard, Transferable contents) {
    System.out.println("lostOwnership: "+clipboard+
" "+contents);
  }
}
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