我已经将此侦听器添加到JLabel中，并且我能够完美地拖动图像，但是，一旦我单击面板（在不存在JLabel的区域中），标签就会返回到它的原始位置。我不知道为什么会发生这种情况。请帮帮我，我已经花了几个小时在这上面工作了。谢谢！
public class CardLabelListener extends MouseAdapter {
private MouseEvent initiateEvent = null;
@Override
public void mouseReleased(MouseEvent me) {
System.err.println("mouse release");
int dx = me.getX() - initiateEvent.getX();
int dy = me.getY() - initiateEvent.getY();
if (Math.abs(dx) > 5 || Math.abs(dy) > 5) {
Rectangle oldBound = me.getComponent().getBounds();
int newX = oldBound.x + dx;
int newY = oldBound.y + dy;
me.getComponent().setBounds(newX, newY, oldBound.width, oldBound.height);
}
initiateEvent = null;
}
public void mousePressed(MouseEvent me) {
GreetingCard.setBackground.findComponentAt(me.getX(), me.getY());
System.err.println("mouse pressed");
initiateEvent = me;
me.consume();
}
public void mouseDragged(MouseEvent me) {
System.err.println(me.getSource());
if (initiateEvent == null) return;
me.consume();
JComponent jc = (JComponent) me.getSource();
TransferHandler handler = jc.getTransferHandler();
handler.exportAsDrag(jc, me, TransferHandler.MOVE);
initiateEvent = null;
}
}
首先，您不是拖动图标，而是拖动组件本身。
其次，您正在与包含标签组件的布局管理器进行斗争。当面板失效时，标签将返回到其原始布局位置。
尝试使用JLayeredPane之类的东西来放置标签
根据反馈更新示例
public class MoveMe {
public static void main(String[] args) {
new MoveMe();
}
public MoveMe() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new MoveMePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class MoveMePane extends JLayeredPane {
public MoveMePane() {
int width = 400;
int height = 400;
for (int index = 0; index < 10; index++) {
String text = "Label " + index;
JLabel label = new JLabel(text);
label.setSize(label.getPreferredSize());
int x = (int) Math.round(Math.random() * width);
int y = (int) Math.round(Math.random() * height);
if (x + label.getWidth() > width) {
x = width - label.getWidth();
}
if (y + label.getHeight() > width) {
y = width - label.getHeight();
}
label.setLocation(x, y);
add(label);
}
MoveMeMouseHandler handler = new MoveMeMouseHandler();
addMouseListener(handler);
addMouseMotionListener(handler);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
}
public class MoveMeMouseHandler extends MouseAdapter {
private int xOffset;
private int yOffset;
private JLabel draggy;
private String oldText;
@Override
public void mouseReleased(MouseEvent me) {
if (draggy != null) {
draggy.setText(oldText);
draggy.setSize(draggy.getPreferredSize());
draggy = null;
}
}
public void mousePressed(MouseEvent me) {
JComponent comp = (JComponent) me.getComponent();
Component child = comp.findComponentAt(me.getPoint());
if (child instanceof JLabel) {
xOffset = me.getX() - child.getX();
yOffset = me.getY() - child.getY();
draggy = (JLabel) child;
oldText = draggy.getText();
draggy.setText("What a drag");
draggy.setSize(draggy.getPreferredSize());
}
}
public void mouseDragged(MouseEvent me) {
if (draggy != null) {
draggy.setLocation(me.getX() - xOffset, me.getY() - yOffset);
}
}
}
}
为此，您需要在JLabel所在的容器上使用null布局，否则该位置将重置为当前布局管理器放置标签的位置。
更好的方法是使用DragLayout
DragLayout旨在取代空布局。它将尊重组件的位置。默认情况下，它将使用组件的首选大小来确定其大小。最后，它将自动计算容器的首选大小。
