JTable Drag and Drop using TransferHandler

Question

Currently I am having two tables say Table-A, Table-B . My task is to drag rows from Table-A to Table-B or drag rows from Table-B on to itself. Using TransferHandler I have achieved this task. But my problem is, I am not able to recognize from which table row was dragged to Table-B .. ie, either from Table-A to Table-B or from Table-B on to itself. In exportData method of TransferHandler I am adding some additional data to one of the column. Basing on this, when I am importing data through importData method I am able to figure out from which table it came using that particular column to which I added data. I know this is not at all recommended .. so I need to know if there is a good way to approach this issue?

Answer 1

You can create your own implementation of Transferable that will have a reference to the source component. Then in TransferHandler.importData() you can compare it with TransferSupport.getComponent() which is a destination component.

For example, here is a wrapper for a string that will be transferred:

public class DataWrapper {
    String data;
    Object source;

    public DataWrapper(String data, Object source) {
        super();
        this.source = source;
        this.data = data;
    }

    public String getData() {
        return data;
    }
    public Object getSource() {
        return source;
    }
}

Here is a very basic Transferable implementation.

public class DataWrapperTransferable implements Transferable {
    public static DataFlavor FLAVOR = new DataFlavor(DataWrapper.class,
            "DataWrapper");

    private DataFlavor flavors[];
    private DataWrapper dataWrapper;

    public DataWrapperTransferable(String data, Object source) {
        dataWrapper = new DataWrapper(data, source);
        flavors = new DataFlavor[] { FLAVOR };
    }

    @Override
    public Object getTransferData(DataFlavor flavor)
            throws UnsupportedFlavorException, IOException {
        if (flavor.equals(FLAVOR)) {
            return dataWrapper;
        } else {
            throw new UnsupportedFlavorException(flavor);
        }
    }

    @Override
    public DataFlavor[] getTransferDataFlavors() {
        return flavors;
    }

    @Override
    public boolean isDataFlavorSupported(DataFlavor flavor) {
        return flavor.equals(FLAVOR) || flavor.equals(DataFlavor.stringFlavor);
    }
}

Then, in TransferHandler :

public boolean importData(TransferSupport support) {
    DataWrapper dataWrapper = (DataWrapper) support
            .getTransferable().getTransferData(
                    DataWrapperTransferable.FLAVOR);

    if (dataWrapper.getSource() == support.getComponent()) {
        //the originator and destination are the same 
    } else {
        //drop from another component
    }               

    //rest of the method
}