这段代码只允许我第二次拒绝一个字符串，试图在textArea中放入一个字符串。
public GridLayoutTest() {
JFrame frame = new JFrame("GridLayout test");
connection = getConnection();
try {
statement = (PreparedStatement) connection
result = statement.executeQuery();
while (result.next()) {
byte[] image = null;
image = result.getBytes("image");
JPanel cellPanel = new JPanel(new BorderLayout());
cellPanel.add(cellLabel, BorderLayout.NORTH);
cellPanel.add(droplabel, BorderLayout.CENTER);
gridPanel.add(cellPanel);
}
}
catch (SQLException e) {
e.printStackTrace();}
}
答案 0 :(得分：3)
所以，有两件事，首先......
public void DropTargetTextArea(String string1, String string2) {
不是构造函数，它是一种方法，请注意void。这意味着它永远不会被调用。这也是DropTargetTextArea textArea = new DropTargetTextArea();工作的原因，当你认为它不应该。
其次，你没有维护对传入（想要成为）构造函数的值的引用，所以你以后无法引用它们......
您可以尝试使用类似......
的内容private String[] values;
public DropTargetTextArea(String string1, String string2) {
values = new String[]{string1, string2};
DropTarget dropTarget = new DropTarget(this, DnDConstants.ACTION_COPY_OR_MOVE, this, true);
}
然后使用像...这样的东西。
if (values[0].equals(dragContents) || values[1].equals(dragContents)) {
在drop方法中。
在您的dragEnter，dragOver和dropActionChanged方法中，您有机会使用dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);或dtde.rejectDrag();等内容来接受或拒绝拖动操作p>
已更新测试代码
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
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.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.io.IOException;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class DragAndDropExample {
public static void main(String[] args) {
ImageIcon ii1 = new ImageIcon("C:\\Users\\Desktop\\home.jpg");
ImageIcon ii = new ImageIcon("C:\\Users\\Desktop\\images (2).jpg");
// Create a frame
JFrame frame = new JFrame("test");
JLabel label = new JLabel(ii);
JLabel label1 = new JLabel(ii1);
JPanel panel = new JPanel(new GridLayout(2, 4, 10, 10));
JLabel testLabel = new DraggableLabel("test");
JLabel testingLabel = new DraggableLabel("testing");
panel.add(testLabel);
panel.add(testingLabel);
panel.add(label);
panel.add(label1);
Component textArea = new DropTargetTextArea("test", "testing");
frame.add(textArea, BorderLayout.CENTER);
frame.add(panel, BorderLayout.SOUTH);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public static class DraggableLabel extends JLabel implements DragGestureListener, DragSourceListener {
DragSource dragSource1;
public DraggableLabel(String text) {
setText(text);
dragSource1 = new DragSource();
dragSource1.createDefaultDragGestureRecognizer(this, DnDConstants.ACTION_COPY_OR_MOVE, this);
}
public void dragGestureRecognized(DragGestureEvent evt) {
Transferable transferable = new StringSelection(getText());
dragSource1.startDrag(evt, DragSource.DefaultCopyDrop, transferable, this);
}
public void dragEnter(DragSourceDragEvent evt) {
System.out.println("Drag enter");
}
public void dragOver(DragSourceDragEvent evt) {
System.out.println("Drag over");
}
public void dragExit(DragSourceEvent evt) {
System.out.println("Drag exit");
}
public void dropActionChanged(DragSourceDragEvent evt) {
System.out.println("Drag action changed");
}
public void dragDropEnd(DragSourceDropEvent evt) {
System.out.println("Drag action End");
}
}
public static class DropTargetTextArea extends JLabel implements DropTargetListener {
private String[] values;
public DropTargetTextArea(String string1, String string2) {
values = new String[]{string1, string2};
DropTarget dropTarget = new DropTarget(this, this);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
public void dragEnter(DropTargetDragEvent evt) {
if (!getText().isEmpty()) {
System.out.println("Reject drag enter");
evt.rejectDrag();
} else {
evt.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
}
}
public void dragOver(DropTargetDragEvent evt) {
if (!getText().isEmpty()) {
System.out.println("Reject drag over");
evt.rejectDrag();
} else {
evt.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
}
}
public void dragExit(DropTargetEvent evt) {
System.out.println("Drop exit");
}
public void dropActionChanged(DropTargetDragEvent evt) {
if (!getText().isEmpty()) {
System.out.println("Reject dropActionChanged");
evt.rejectDrag();
} else {
evt.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
}
}
public void drop(DropTargetDropEvent evt) {
if (!getText().isEmpty()) {
evt.rejectDrop();
} else {
try {
Transferable transferable = evt.getTransferable();
if (transferable.isDataFlavorSupported(DataFlavor.stringFlavor)) {
String dragContents = (String) transferable.getTransferData(DataFlavor.stringFlavor);
evt.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
if (values[0].equals(dragContents) || (values[1]).equals(dragContents)) {
System.out.println("Accept Drop");
setText(getText() + " " + dragContents);
evt.getDropTargetContext().dropComplete(true);
} else {
System.out.println("Reject Drop");
}
}
} catch (IOException e) {
evt.rejectDrop();
evt.dropComplete(false);
} catch (UnsupportedFlavorException e) {
}
}
}
}
}