从JTable拖放到JLayeredPane

问题描述：

如何在 JTable 和 JLayeredPane 之间创建拖放.

How to create Drag and drop between JTable and JLayeredPane.

有没有人知道如何实现这一目标?

Does anyone have any ideas how to implement this?

我需要通过拖放在JTable和JLayeredPane之间传输对象.

答

您必须至少做几件事才能使它起作用:

You have to do a few things at minimum to get this to work:

在您的JTable实例上调用setDragEnabled(true)
设置JTable和JLayeredPane的

Call setDragEnabled(true) on your JTable instance
Set the JTables and JLayeredPanes DropTarget
Create a draggable Component to add to the JLayeredPane

要设置Component s DropTarget，请调用setDropTarget(DropTarget d)方法并传递一个匿名内部类作为参数.删除 Transferable 的代码> s到Component的数据应该位于drop(DropTargetDropEvent dtde)方法中.

To set a Components DropTarget, call the setDropTarget(DropTarget d) method and pass an anonymous inner class as the argument. Code that drops the Transferables data into the Component should be located in the drop(DropTargetDropEvent dtde) method.

下面的代码片段显示了如何接收Transferable并将其插入到发起放置的JTable行中:

The below snippet shows how to receive a Transferable and insert it into the row of a JTable where the drop was initiated:

table.setDropTarget(new DropTarget() {

    @Override
    public synchronized void drop(DropTargetDropEvent dtde) {
        try {
            // get row to put new item in
            int row = table.rowAtPoint(dtde.getLocation());
            // inserting row:
            ((DefaultTableModel) table.getModel()).insertRow(
                    //if the row wasn't found, add it to the end of the JTable
                    row == -1 ? table.getRowCount() : row,
                    // pass string flavor of transferable data as row data parameter
                    new Object[] {dtde.getTransferable()
                                .getTransferData(DataFlavor.stringFlavor)});
        } catch(UnsupportedFlavorException | IOException e) {
            e.printStackTrace();
        }
    }
});

下面的代码片段再次接收到Transferable，但是将其添加到JLayeredPane的末尾.请注意，因为我为JLayeredPane分配了BoxLayout(SwingConstants.VERTICAL)，所以组件被添加到了JLayeredPane的末尾.

This below snippet again receives a Transferable but instead adds it to the end of a JLayeredPane. Note that components are added to the end of the JLayeredPane because I assign a BoxLayout(SwingConstants.VERTICAL) to it.

layeredPane.setDropTarget(new DropTarget() {

    @Override
    public synchronized void drop(DropTargetDropEvent dtde) {
        try {
            // create draggable label to add to layered pane 
            // creating this class will be explained next
            final DraggableLabel label = new DraggableLabel(
                    (String) dtde.getTransferable()
                    .getTransferData(DataFlavor.stringFlavor));

            // add label to layered pane
            layeredPane.add(label, JLayeredPane.DEFAULT_LAYER);
            layeredPane.revalidate();
            layeredPane.repaint();
        } catch(UnsupportedFlavorException | IOException e) {
            e.printStackTrace();
        }
    }

});

要创建可拖动的Component(在本示例中为JLabel)，您必须:

To create a draggable Component (In this example a JLabel), you must:

创建一个新的类，该类extends JLabel和implements DragGestureListener 和 DragSourceListener
覆盖所有必需的方法

在构造函数中:

创建一个新的 DragSource
创建 DragGestureRecognizer 并将其分配给this JLabel子类和this DragGestureListener

Create a new class that extends JLabel and implements DragGestureListener and DragSourceListener
Override all the necessary methods

In the constructor:

Create a new DragSource
Create a DragGestureRecognizer and assign it to this the JLabel subclass and this the DragGestureListener

class DraggableLabel extends JLabel implements DragGestureListener, DragSourceListener {

    private DragSource dragSource;

    DraggableLabel(String text) {
        super(text);

        // create the drag source
        dragSource = new DragSource();
        // assign this component a DragGestureRecognizer
        dragSource.createDefaultDragGestureRecognizer(
                this, DnDConstants.ACTION_COPY_OR_MOVE, this);

        // for contrast with other items in layered pane
        setBorder(BorderFactory.createLineBorder(Color.DARK_GRAY));
    }

    @Override
    public void dragGestureRecognized(DragGestureEvent evt) {
        dragSource.startDrag(
                evt, //trigger event
                DragSource.DefaultMoveDrop, // icon
                new StringSelection(getText()), // transferable data
                this); // this the DragSourceListener
    }

    @Override
    public void dragEnter(DragSourceDragEvent evt) {}

    @Override
    public void dragOver(DragSourceDragEvent evt) {}

    @Override
    public void dragExit(DragSourceEvent evt) {}

    @Override
    public void dropActionChanged(DragSourceDragEvent evt) {}

    @Override
    public void dragDropEnd(DragSourceDropEvent evt) {}

}

完整的示例:

Full working example:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDropEvent;
import java.io.IOException;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JLayeredPane;
import javax.swing.JTable;
import javax.swing.WindowConstants;
import javax.swing.table.DefaultTableModel;

class DragDropExample {

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            final JFrame frame = new JFrame("JLabel Text Example");

            final JTable table = new JTable(new DefaultTableModel(
                    new Object[][] {
                            {"Item 1"},
                            {"Item 2"},
                            {"Item 3"},
                            {"Item 4"},
                            {"Item 5"}},
                    new String[] {"Column Name"}));
            table.setDragEnabled(true);
            table.setDropTarget(new DropTarget() {

                @Override
                public synchronized void drop(DropTargetDropEvent dtde) {
                    try {
                        // get row to put new item in
                        int row = table.rowAtPoint(dtde.getLocation());
                        // inserting row:
                        ((DefaultTableModel) table.getModel()).insertRow(
                                //if the row wasn't found, add it to the end of the JTable
                                row == -1 ? table.getRowCount() : row,
                                // pass string flavor of transferable data as row data parameter
                                new Object[] {dtde.getTransferable()
                                        .getTransferData(DataFlavor.stringFlavor)});
                    } catch(UnsupportedFlavorException | IOException e) {
                        e.printStackTrace();
                    }
                }
            });

            final JLayeredPane layeredPane = new JLayeredPane() {

                @Override
                public Dimension getPreferredSize() {
                    return new Dimension(200, 300);
                }

            };
            layeredPane.setBorder(BorderFactory.createLineBorder(Color.BLACK));
            layeredPane.setLayout(new BoxLayout(layeredPane, BoxLayout.Y_AXIS));
            layeredPane.setDropTarget(new DropTarget() {

                @Override
                public synchronized void drop(DropTargetDropEvent dtde) {
                    try {
                        // create draggable label to add to layered pane
                        // creating this class will be explained next
                        final DraggableLabel label = new DraggableLabel(
                                (String) dtde.getTransferable()
                                        .getTransferData(DataFlavor.stringFlavor));

                        // add label to layered pane
                        layeredPane.add(label, JLayeredPane.DEFAULT_LAYER);
                        layeredPane.revalidate();
                        layeredPane.repaint();
                    } catch(UnsupportedFlavorException | IOException e) {
                        e.printStackTrace();
                    }
                }

            });

            frame.getContentPane().add(table, BorderLayout.WEST);
            frame.getContentPane().add(layeredPane);
            frame.pack();
            frame.setLocationByPlatform(true);
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            frame.setVisible(true);
        });
    }

    static class DraggableLabel extends JLabel implements DragGestureListener, DragSourceListener {

        private DragSource dragSource;

        DraggableLabel(String text) {
            super(text);

            // create the drag source
            dragSource = new DragSource();
            // assign this component a DragGestureRecognizer
            dragSource.createDefaultDragGestureRecognizer(
                    this, DnDConstants.ACTION_COPY_OR_MOVE, this);

            // for contrast with other items
            setBorder(BorderFactory.createLineBorder(Color.DARK_GRAY));
        }

        @Override
        public void dragGestureRecognized(DragGestureEvent evt) {
            dragSource.startDrag(
                    evt, //trigger event
                    DragSource.DefaultMoveDrop,
                    new StringSelection(getText()),
                    this);
        }

        @Override
        public void dragEnter(DragSourceDragEvent evt) {}

        @Override
        public void dragOver(DragSourceDragEvent evt) {}

        @Override
        public void dragExit(DragSourceEvent evt) {}

        @Override
        public void dropActionChanged(DragSourceDragEvent evt) {}

        @Override
        public void dragDropEnd(DragSourceDropEvent evt) {}

    }

}

从JTable拖放到JLayeredPane

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