在 Java 中从 JButton 拖放到 JComponent [英] Drag and Drop from JButton to JComponent in Java
问题描述
我在互联网上搜索了如何将 JButtons 拖放到对象的示例，但我无法使其工作.
我的程序所做的是，当我单击按钮时，对象会更新一个字段(使用 selectedobject.setField()).我希望能够通过单击而不是通过拖动 JButton 来做到这一点.
我该怎么做?我找到了这个，并尝试输入我的代码:
btn.setTransferHandler(new ImageHandler());btn.addMouseListener(新鼠标适配器(){公共无效鼠标按下(鼠标事件e){JComponent c = (JComponent)e.getSource();TransferHandler 处理程序 = c.getTransferHandler();handler.exportAsDrag(c, e, TransferHandler.COPY);}});我从 作为另一个示例...
I searched on the internet for examples how to Drag and Drop JButtons to an Object but I could not make it work.
What my program does, is that when I click on a button, the object updated a field (with a selectedobject.setField()). I want to be able to do this not by clicking, but by dragging the JButton.
How can I do this ? I found this, and I tried to put in 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.
Drag'n'drop is a fun bag of crunchy, munchy carrots...not helped by the fact that there is a "core" API and the newer "transfer" API, so it's really easy to get confused
The following example uses the "transfer" API and basically transfers a String value from a button to a 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've gone out my way to separate the TransferHandlers allowing for a "drag" and "drop" version. You don't "have" to do this and you "could" use a single TransferHandler to perform both operations, that's up to you.
You will have to modify the ValueExportTransferHandler to accept different values and modify the SUPPORTED_DATE_FLAVOR accordingingly, but those are the basics
You could also have a look at Drag and Drop custom object from JList into JLabel as another example...
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