Drag and Drop from JButton to JComponent in Java

Question

I searched the Internet for examples of using Drag and Drop JButtons for an object, but I could not get it to work.

What my program does is that when I click the button, the object updates the field (with the selected object object.setField ()). I want to do this without clicking and dragging JButton.

How can i do this? I found this and I tried to insert my code:

btn.setTransferHandler(new ImageHandler()); btn.addMouseListener(new MouseAdapter() { public void mousePressed(MouseEvent e) { JComponent c = (JComponent)e.getSource(); TransferHandler handler = c.getTransferHandler(); handler.exportAsDrag(c, e, TransferHandler.COPY); } }); 

I took the ImageHandler class from here .

Answer 1

Drag'n'drop is a fun bag of crispy, buzzing carrots ... the fact that there is a "main" API and the newest "transfer" API does not help, so it’s very easy to get confused

The following example uses the "transfer" API and basically passes the String value from the button to JLabel .

 import java.awt.Color; import java.awt.Component; import java.awt.EventQueue; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.GridLayout; import java.awt.datatransfer.DataFlavor; import java.awt.datatransfer.StringSelection; import java.awt.datatransfer.Transferable; import java.awt.dnd.DnDConstants; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import javax.swing.JButton; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.TransferHandler; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; import javax.swing.border.CompoundBorder; import javax.swing.border.EmptyBorder; import javax.swing.border.LineBorder; public class Test { public static void main(String[] args) { new Test(); } public Test() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { ex.printStackTrace(); } JFrame frame = new JFrame("Testing"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(new TestPane()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } public class TestPane extends JPanel { public TestPane() { setLayout(new GridLayout(1, 2)); add(createLeftPanel()); add(createRightPanel()); } protected JPanel createLeftPanel() { JPanel panel = new JPanel(new GridBagLayout()); GridBagConstraints gbc = new GridBagConstraints(); gbc.gridwidth = GridBagConstraints.REMAINDER; gbc.fill = GridBagConstraints.HORIZONTAL; gbc.weightx = 1; for (int index = 0; index < 10; index++) { JButton btn = new JButton(Integer.toString(index + 1)); panel.add(btn, gbc); btn.setTransferHandler(new ValueExportTransferHandler(Integer.toString(index + 1))); btn.addMouseMotionListener(new MouseAdapter() { @Override public void mouseDragged(MouseEvent e) { JButton button = (JButton) e.getSource(); TransferHandler handle = button.getTransferHandler(); handle.exportAsDrag(button, e, TransferHandler.COPY); } }); } return panel; } protected JPanel createRightPanel() { JPanel panel = new JPanel(new GridBagLayout()); JLabel label = new JLabel("Drop in"); label.setBorder(new CompoundBorder(new LineBorder(Color.DARK_GRAY), new EmptyBorder(20, 20, 20, 20))); label.setTransferHandler(new ValueImportTransferHandler()); panel.add(label); return panel; } } public static class ValueExportTransferHandler extends TransferHandler { public static final DataFlavor SUPPORTED_DATE_FLAVOR = DataFlavor.stringFlavor; private String value; public ValueExportTransferHandler(String value) { this.value = value; } public String getValue() { return value; } @Override public int getSourceActions(JComponent c) { return DnDConstants.ACTION_COPY_OR_MOVE; } @Override protected Transferable createTransferable(JComponent c) { Transferable t = new StringSelection(getValue()); return t; } @Override protected void exportDone(JComponent source, Transferable data, int action) { super.exportDone(source, data, action); // Decide what to do after the drop has been accepted } } public static class ValueImportTransferHandler extends TransferHandler { public static final DataFlavor SUPPORTED_DATE_FLAVOR = DataFlavor.stringFlavor; public ValueImportTransferHandler() { } @Override public boolean canImport(TransferHandler.TransferSupport support) { return support.isDataFlavorSupported(SUPPORTED_DATE_FLAVOR); } @Override public boolean importData(TransferHandler.TransferSupport support) { boolean accept = false; if (canImport(support)) { try { Transferable t = support.getTransferable(); Object value = t.getTransferData(SUPPORTED_DATE_FLAVOR); if (value instanceof String) { Component component = support.getComponent(); if (component instanceof JLabel) { ((JLabel) component).setText(value.toString()); accept = true; } } } catch (Exception exp) { exp.printStackTrace(); } } return accept; } } } 

I have come my way to separate TransferHandler , allowing the drag and drop version. You do not have “this,” and you “can” use one TransferHandler to perform both of the operations that are available to you.

You will need to change the ValueExportTransferHandler to accept different values ​​and change SUPPORTED_DATE_FLAVOR , essentially, but these are the basics

You can also take a look at dragging and dropping a custom object from JList to JLabel as another example ...