jfreechart的chartpanel生成Image对象的问题

Question

我要做的功能是将jfreechart生成的图复制到windows的剪切板上但是chartpanel.createImage(chartpanel.getWidth(),chartpanel.getHeight());返回的是空
我希望这个chartpanel能生成一个Image对象
请教熟悉jfreechart的人指导下

Answer 1

先透過 ChartFactory 產生一個JFreeChat，然後用JFreeChart的 createBufferedImage 產生圖，
或是 draw(java.awt.Graphics2D ...)那些 method 把圖畫在別的元件的 Graphics2D 上。

Answer 2

ChartPanel chartPanel=chartSrivice.makePieChart(this.getPieChartData(
                        titles, tableData));
JPopupMenu popupMenu=chartPanel.getPopupMenu();
JMenuItem menuItem=new JMenuItem("Copy");
final Image image = chartPanel.getChart().createBufferedImage(chartPanel.getWidth(), chartPanel.getHeight());
 menuItem.addActionListener(new ActionListener()
        {            public void actionPerformed(ActionEvent event)
            {
                
                Clipboard board=Toolkit.getDefaultToolkit().getSystemClipboard();
                 
                Transferable trans = new Transferable()
                {                    public DataFlavor[] getTransferDataFlavors()
                    {
                        return new DataFlavor[] { DataFlavor.imageFlavor };
                    }                    public boolean isDataFlavorSupported(DataFlavor flavor)
                    {
                        return DataFlavor.imageFlavor.equals(flavor);
                    }                    public Object getTransferData(DataFlavor flavor)
                            throws UnsupportedFlavorException, IOException
                    {
                        if (isDataFlavorSupported(flavor)){
                            return image;}
                        throw new UnsupportedFlavorException(flavor);
                    }                };
                board.setContents(trans, null);            }
            
        });
        popupMenu.add(menuItem);红色字体那报错了，java.lang.IllegalArgumentException: Width (0) and height (0) cannot be <= 0。
这是什么问题啊，我希望从chartpanel对象获得image对象，应该怎么做

Answer 3

是不是我思路错了，有没有人知道jpanel怎么转Image对象，或者说复制功能不用这么做

Answer 4

先參考這個頁面做出ImageSelection 
ImageSelection 最後產生JFreeChart之後用下面這段程式複製到剪貼簿。 Clipboard clipboard = java.awt.Toolkit.getDefaultToolkit().getSystemClipboard();
 ImageSelection imgSel = new ImageSelection(jfreeChart.createBufferedImage(400, 300));
 Toolkit.getDefaultToolkit().getSystemClipboard().setContents(imgSel, null);

Answer 5

问题解决了，原因是chartPanel只有在画到面板上以后才能取出长和宽。在触发事件的时候再获取chartPanel的大小生成imag对象就行了。修改如下方法就可以了
 public Object getTransferData(DataFlavor flavor)
                            throws UnsupportedFlavorException, IOException
                    {
                        if (isDataFlavorSupported(flavor)){
                            Image image =chartPanel.getChart().createBufferedImage(chartPanel.getWidth(), chartPanel
                                    .getHeight());
                            return image;}
                        throw new UnsupportedFlavorException(flavor);
                    }