Java. Drag & Drop ImageIcon from JLabel on panel 1, to JLabel on panel 2. Add Counter function

问题

I've implemented this very basic, drag and drop between two JPanels, but this doesn't really meet my requirements!

public class test extends JFrame {

{    JPanel mainpanel, storypanel, imageselect;



    public test(){

          mainpanel = new JPanel(new BorderLayout());
          storypanel = new JPanel();
          imageselect = new JPanel();
            MouseListener listener = new MouseAdapter(){
            public void mousePressed(MouseEvent e)
        {
            JComponent c = (JComponent) e.getSource();
            TransferHandler handler = c.getTransferHandler();
            handler.exportAsDrag(c, e, TransferHandler.COPY);
        }
        };

            int j = 0;
            BufferedImage myImages;
            JLabel imgselect = new JLabel();
            try { myImages = ImageIO.read(new File("four.jpg"));
            //myImages[j] = resize(myImages[j]);
            imgselect= new JLabel(new ImageIcon(myImages));
            System.out.println(j);
            imageselect.add(imgselect);
            imgselect.addMouseListener(listener);
            imgselect.setTransferHandler(new TransferHandler("icon"));

            } catch(Exception e) {};

            int i = 0;
            BufferedImage storyimages;
            JLabel storylabel = new JLabel();


            //targetImg = new ImageIcon("lmkpackage/base/TargetImg.jpg");
            try{ storyimages = ImageIO.read(new File("TargetImg.jpg"));
            //storyimages[i] = resize(storyimages[i]);
            storylabel = new JLabel(new ImageIcon(storyimages));
            System.out.println(i);
            storypanel.add(storylabel); 
            storylabel.addMouseListener(listener);
            storylabel.setTransferHandler(new TransferHandler("icon"));
            } catch(Exception e) {};


            mainpanel.add(imageselect, BorderLayout.NORTH);
            mainpanel.add(storypanel, BorderLayout.SOUTH);

            getContentPane().add(mainpanel);



        }

        public static void main(String[] args){

        System.out.println("Application Running");
        JFrame mainframe =  new test();
            mainframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainframe.setSize(1000,1000);
            mainframe.setVisible(true);

        }

    }

Sorry I wasn't very clear here. Im trying to drag an ImageIcon from a JLabel on the imageselect panel, to another JLabel the storyline panel. I can do this, with the above code. But when I do this, I can drag an ImageIcon from the imageselect panel, and replace another ImageIcon on the same panel. I do NOT want this to happen. I can also drag from the storyline panel to the imageselect panel, which I do NOT want.

I'm not asking to be spoon fed code, I'm just looking for a push in the right direction!

EDIT: I'm wondering is there any way of counting a successful drag and drop operation, the solution below answered my original question.

回答1:

This is basically an outline of @Andrew's comment - easily possible due to your SSCCE :-)

Subclass TransferHandler, override canImport to check if the source label is on the imageSelect panel and reject if so.

    // custom transferHandler which decides about imports based on source
    TransferHandler handler = new TransferHandler("icon") {

        @Override
        public boolean canImport(TransferSupport support) {
            return super.canImport(support) 
                    && support.getComponent().getParent() != imageSelectPanel;
        }

    };
    // use the handler on all labels (handlers can be shared, btw)
    // for each label on imageSelectPanel
    imageSelectLabel.setTransferHandler(handler)
    // for each label on the target panel (aka storyPanel) 
    storyLabel.setTransferHandler(handler)

来源：https://stackoverflow.com/questions/9486118/java-drag-drop-imageicon-from-jlabel-on-panel-1-to-jlabel-on-panel-2-add-c

标签

java

swing

drag-and-drop

jlabel