为什么 JMenu 不总是在最前面?

2022-01-24 00:00:00 java swing jframe jmenu

在使用 JButton 更新 JFrame 上的 JTable 之前，JMenu 行为正常.然后 JMenu 主要被 JPanel 隐藏(见下图).JMenu 不应该在被选中时始终位于顶部吗?为什么被推到后面?更新 jButtonAddActionPerformed 上的表的代码是.

The JMenu behaves normally until a JButton is used to update a JTable on the JFrame. Then the JMenu is mostly hidden by a JPanel (see images below). Shouldn't the JMenu always be on top when it is selected? Why has it been pushed to the back? The code that updates the table on jButtonAddActionPerformed is.

public class MyClass extends javax.swing.JFrame {
    private void jButtonAddActionPerformed(java.awt.event.ActionEvent evt) {
        DefaultTableModel model = (DefaultTableModel) jTable.getModel();
        model.addRow(new Object[]{"", DEFAULT_ON, DEFAULT_OFF});
        int lastRow = jTable.getRowCount() - 1;
        jTable.setValueAt(lastRow + 1, lastRow, 0);
    }                                                  
...

预期

坏了

推荐答案

可能是因为你在使用 JPanel 时使用的是 Canvas.Canvas 是一个 AWT 组件，绘制在 Swing 组件之上.不要在 Swing 应用程序中使用 AWT 组件.

Probably because you are using a Canvas when you should be using a JPanel. Canvas is an AWT component and is painted on top of Swing components. Don't use AWT components in a Swing application.

如果您确实需要使用 AWT 组件，那么您需要 JDK 的当前版本.查看混合重质和轻质成分.

If you really need to use an AWT component then you need a current release of the JDK. See Mixing Heavy and Light Components.

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