當我將ActionListeners與Drag'n'Drop組合時,會遇到意外的行爲。意外操作在拖動後執行
運行下面的例子,請嘗試以下操作:
- 拖動按鈕一個的地方,並釋放mousebutton
- 不要將鼠標移動到按鈕A再次
- 點擊按鈕乙
- 在System.out上,您將看到actionPerformed將針對按鈕A和b的
我不想打電話的actionPerformed的按鈕一個。我究竟做錯了什麼?
下面是完整的例子:
import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.awt.event.*;
import java.io.IOException;
import javax.swing.*;
public class DragDropTest{
private static Color slightlyRed = new Color(255, 220, 220);
private static Color slightlyGreen = new Color(220, 255, 220);
private static class DragDropButton extends JButton implements DragSourceListener, DragGestureListener, Transferable, ActionListener{
private DragSource dragSource;
public DragDropButton(String string) {
super(string);
addActionListener(this);
dragSource = new DragSource();
dragSource.createDefaultDragGestureRecognizer(this, DnDConstants.ACTION_COPY, this);
}
// Interface DragSourceListener
@Override public void dragEnter(DragSourceDragEvent dsde) {}
@Override public void dragOver(DragSourceDragEvent dsde) {}
@Override public void dropActionChanged(DragSourceDragEvent dsde) {}
@Override public void dragExit(DragSourceEvent dse) {}
@Override public void dragDropEnd(DragSourceDropEvent dsde) {
System.out.println("Dragging of [" + getText() + "] ended");
}
// Interface DragGestureListener
@Override public void dragGestureRecognized(DragGestureEvent dge) {
dragSource.startDrag(dge, DragSource.DefaultMoveDrop, this, this);
}
// Interface Transferable
@Override public DataFlavor[] getTransferDataFlavors() {return null;}
@Override public boolean isDataFlavorSupported(DataFlavor flavor) {return false;}
@Override public Object getTransferData(DataFlavor flavor)
throws UnsupportedFlavorException, IOException {return null;}
// Interface ActionListener
@Override public void actionPerformed(ActionEvent e) {
System.out.println("Action on [" + getText() + "]");
}
}
private static class DropPanel extends JPanel implements DropTargetListener{
public DropPanel(){
setBorder(BorderFactory.createLineBorder(Color.BLACK));
setPreferredSize(new Dimension(300, 300));
setBackground(slightlyGreen);
new DropTarget(this, this);
}
@Override public void dragEnter(DropTargetDragEvent dtde) {}
@Override public void dragOver(DropTargetDragEvent dtde) {}
@Override public void dropActionChanged(DropTargetDragEvent dtde) {}
@Override public void dragExit(DropTargetEvent dte) {}
@Override public void drop(DropTargetDropEvent dtde) {
System.out.println("Drop complete");
dtde.dropComplete(true);
}
}
// Create Panels
private static JPanel leftSide(){
JPanel leftPanel = new JPanel();
leftPanel.setPreferredSize(new Dimension(300, 300));
leftPanel.setBackground(slightlyRed);
leftPanel.add(new DragDropButton("A"));
leftPanel.add(new DragDropButton("B"));
return leftPanel;
}
private static JPanel rightSide(){
JPanel leftPanel = new DropPanel();
return leftPanel;
}
// Create Window
private static JFrame boringFrame(String text){
JFrame boringFrame = new JFrame(text);
boringFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
boringFrame.getContentPane().setLayout(new FlowLayout(FlowLayout.CENTER));
boringFrame.setVisible(true);
return boringFrame;
}
public static void main(String[] args){
JFrame boringFrame = boringFrame("boring");
boringFrame.add(leftSide());
boringFrame.add(rightSide()); // try to comment out this line!
boringFrame.pack();
}
}
有在我的項目多了一些問題,但我不會打擾你跟他們,因爲似乎這是我的問題的主要來源,但這裏是另一個觀察我發的:
如果沒有DropTargetListener(就像我的DropPanel),問題就會消失。嘗試註釋掉以下行:
boringFrame.add(rightSide());
是否要發生鼠標拖動事件而不是執行操作? – zari
拖動事件按預期發生。先前拖動的按鈕的額外操作使我困擾。 – MyPasswordIsLasercats
因此,您可以將鼠標拖動事件偵聽器添加到您的表單中,而不是您的按鈕。 – zari