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我正在構建一個應用程序，它將標籤置於用戶在面板（jpanel2）上單擊並允許其移動放置的標籤的地方。JLabel在試圖拖動時消失
我可以成功放置標籤，但我無法移動任何標籤。事實上，當我嘗試拖動一個標籤時，它就消失了，在我所有的嘗試中。 我也嘗試在jPanel2和JFrame中調用重繪，但仍然沒有成功。
JPanel 2沒有Layout（免費設計），希望將標籤完全放在鼠標點擊的位置。
UPDATE
這是發生問題的一個小例子。 我無法減少面板的數量，因爲我需要在屏幕上放置更多控件（例如jtable，菜單和工具欄）。
public class Example extends javax.swing.JFrame {
static int count = 0;
public Example() {
initComponents();
}
@SuppressWarnings("unchecked")
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jPanel2 = new javax.swing.JPanel();
jPanel3 = new javax.swing.JPanel();
jLabel1 = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setPreferredSize(new java.awt.Dimension(600, 600));
jPanel2.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jPanel2MouseClicked(evt);
}
});
jPanel3.setMinimumSize(new java.awt.Dimension(0, 0));
jPanel3.setLayout(new java.awt.BorderLayout());
jPanel3.add(jLabel1, java.awt.BorderLayout.CENTER);
javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
jPanel2.setLayout(jPanel2Layout);
jPanel2Layout.setHorizontalGroup(
jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
jPanel2Layout.setVerticalGroup(
jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addComponent(jPanel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addContainerGap())
);
getContentPane().add(jPanel1, java.awt.BorderLayout.CENTER);
pack();
}// </editor-fold>
private void jPanel2MouseClicked(java.awt.event.MouseEvent evt) {
count++;
addAnnotation(String.valueOf(count), evt.getX(), evt.getY());
}
private void addAnnotation(String labelStr, int x, int y) {
final JLabel label = new JLabel(labelStr);
jPanel2.add(label);
label.setLocation(x, y);
System.out.println("Adding to " + x + " " + y);
label.setSize(20, 20);
label.setBackground(Color.WHITE);
label.setOpaque(true);
label.setBorder(new LineBorder(Color.BLACK, 1, false));
label.setHorizontalAlignment(SwingConstants.CENTER);
label.setVisible(true);
label.setForeground(Color.BLACK);
label.addMouseMotionListener(new MouseMotionListener() {
@Override
public void mouseDragged(MouseEvent e) {
Component c = e.getComponent();
int moveToX = c.getX() + e.getX();
int moveToY = c.getY() + e.getY();
c.setLocation(moveToX, moveToY);
System.out.println("Moving to " + moveToX + " " + moveToY);
}
@Override
public void mouseMoved(MouseEvent e) {
}
});
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Example.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Example().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JPanel jPanel3;
// End of variables declaration
}
您將要創建和發佈[小例子（http://stackoverflow.com/help/mcve）（請參閱鏈接），如果你想擁有獲得體面的幫助的最好的機會。 –
對不起@HovercraftFullOfEels。我已經更新了一個最小的例子，其中的問題可以被複制:)謝謝你的頭！ –
請重新閱讀鏈接。你最小的例子實際上應該是** minimal **，並且沒有任何與你的問題無關的無關代碼，例如日誌記錄或者NetBeans生成的代碼。只需通過手工編碼創建一個小型圖形用戶界面，即可重現問題併發布。 –