我正在尝试在同一应用程序的不同实例之间实现对象的复制粘贴。目前它只适用于一个应用程序（我的意思是，在同一个应用程序实例中复制和粘贴），但在不同实例之间不起作用。
复制代码：
// MyObject is a class of objects I want to copy/paste;
// MyObjectSelection is a class that impements Transferable and ClipboardOwner interfaces
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
MyObject data = new MyObject(selectedItems);
MyObjectSelection dataSelection = new MyObjectSelection(data);
clipboard.setContents(dataSelection, this);
之后，我可以检查剪贴板的内容，如下所示：
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
Transferable clipboardContent = clipboard.getContents(this);
DataFlavor[] flavors = clipboardContent.getTransferDataFlavors();
System.out.println("flavors.length=" + flavors.length);
for (int i = 0; i < flavors.length; i++){
System.out.println("flavor=" + flavors[i]);
}
如果我从复制对象的同一个应用程序实例中执行此操作，它可以工作：flavors.lengthis 1， mimetype is application/x-java-serialized-object，而且，它可以工作。
但是如果我打开应用程序，执行复制，然后再次打开同一个应用程序（第一个没有关闭，即两个实例同时运行），并尝试从那里检查剪贴板内容，然后flavors.length是0.
我检查了文档和这些示例：one , two，但我仍然找不到我的实现中有什么问题。
我错过了什么？
UPD：我添加了 sscce: clipboard_test.zip。
这是包含 3 个源文件的测试应用程序（我使用 Eclipse 构建它）：
ClipboardTest.java- 主应用程序类MyObject.java- 用于复制/粘贴对象的类（此类仅包含数组String）MyObjectSelection.java- 实现Transerable和ClipboardOwner接口的类有两个按钮：“复制”、“测试”。
当您按下“复制”按钮时，将创建 MyObject 的新实例并将其放入剪贴板。
当您按下“测试”按钮时，将检查剪贴板内容并将其回显到控制台（支持
DataFlavor的计数和每个DataFlavor）所以，复制这些步骤：
开始申请
- 按“复制”按钮：您将
"object copied"在日志中看到消息 按“测试”按钮：您将看到剪贴板的内容：
flavors.length = 1 flavor[0] = java.awt.datatransfer.DataFlavor[mimetype=application/x-java-serialized-object;representationclass=MyObject]启动应用程序的另一个实例（不要关闭第一个）
按“测试”按钮：你会看到剪贴板是空的：
flavors.length = 0
这是为什么？
UPD2： sscce 直接在这里发布：
import java.awt.BorderLayout;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.ClipboardOwner;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.Toolkit;
import javax.swing.JButton;
import javax.swing.SwingUtilities;
import javax.swing.JFrame;
public final class ClipboardTest implements Runnable, ClipboardOwner {
public static void main(String[] args) {
SwingUtilities.invokeLater (new ClipboardTest());
}
public void run() {
JFrame f = new JFrame ("Clipboard test");
f.setDefaultCloseOperation (JFrame.DISPOSE_ON_CLOSE);
//-- Create "copy" button.
// When you click it, new object "test_items" becomes created
// and put to the clipboard.
{
JButton button_copy = new JButton("copy");
button_copy.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
String[] test_items = {
"one", "two", "three"
};
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
MyObject data = new MyObject(test_items);
MyObjectSelection dataSelection = new MyObjectSelection(data);
clipboard.setContents(dataSelection, ClipboardTest.this);
System.out.println("object copied");
}
});
f.add(button_copy, BorderLayout.NORTH);
}
//-- Create "test" button.
// When you click it, clipboard contents are checked
// and echoed to the console (count of supported DataFlavor's, and each DataFlavor)
{
JButton button_test = new JButton("test");
button_test.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
Transferable clipboardContent = clipboard.getContents(this);
DataFlavor[] flavors = clipboardContent.getTransferDataFlavors();
System.out.println("flavors.length = " + flavors.length);
for (int i = 0; i < flavors.length; i++){
System.out.println("flavor[" + i + "] = " + flavors[i]);
}
}
});
f.add(button_test, BorderLayout.SOUTH);
}
f.pack();
f.setVisible(true);
}
// ClipboardOwner implementation
@Override
public void lostOwnership(Clipboard clipboard, Transferable transferable){
System.out.println("ClipboardTest: Lost ownership");
}
/* *****************************************************************************************
* Object that I want to copy/paste
* ****************************************************************************************/
public static class MyObject {
private String[] items;
public MyObject(String[] items){
this.setItems(items);
}
public String[] getItems(){
return this.items;
}
public void setItems(String[] items){
this.items = items;
}
}
public static class MyObjectSelection implements Transferable, ClipboardOwner {
private static DataFlavor dmselFlavor = new DataFlavor(MyObject.class, "Test data flavor");
private MyObject selection;
public MyObjectSelection(MyObject selection){
this.selection = selection;
}
// Transferable implementation
@Override
public DataFlavor[] getTransferDataFlavors(){
System.out.println("getTransferDataFlavors");
DataFlavor[] ret = {dmselFlavor};
return ret;
}
@Override
public boolean isDataFlavorSupported(DataFlavor flavor){
return dmselFlavor.equals(flavor);
}
@Override
public synchronized Object getTransferData (DataFlavor flavor)
throws UnsupportedFlavorException
{
if (isDataFlavorSupported(flavor)){
return this.selection;
} else {
throw new UnsupportedFlavorException(dmselFlavor);
}
}
// ClipboardOwner implementation
@Override
public void lostOwnership(Clipboard clipboard, Transferable transferable){
System.out.println("MyObjectSelection: Lost ownership");
}
}
}