JCombobox with actionperformed in another actionperformed

Question

我正在尝试制作一个 Combobox，其中 actionperformed 在另一个 actionperformed 中。这个想法是你从一个带有按钮的屏幕开始，点击按钮后添加组合框。当我尝试添加组合框时，错误显示 "vlaggenlijst cannot be resolved to a variable"。

这是我制作组合框的代码：

JComboBox vlaggenlijst = new JComboBox(vlaggen);
vlaggenlijst.setSelectedIndex(0);
vlaggenlijst.addActionListener(this);

这是 actionPerformed 中的代码：

if(event.getSource() == b1) {
        Container parentft = FirstText.getParent();
        parentft.remove(FirstText);
        parentft.validate();
        parentft.repaint();

        Title.setText("Vlaggen");

        Container parentb1 = b1.getParent();
        parentb1.remove(b1);
        parentb1.validate();
        parentb1.repaint();

        add(vlaggenlijst, BorderLayout.PAGE_START);

        add(Picture, BorderLayout.CENTER);

        if(event.getSource() == vlaggenlijst){
            JComboBox cb = (JComboBox)event.getSource();
            String vlagnaam = (String)cb.getSelectedItem();
            updateLabel(vlagnaam);
        }
}

谁能帮帮我，我真的不知道哪里错了。非常感谢。

Answer 1

将JComboBox vlaggenlijst声明为字段而非局部变量例如：

private JComboBox vlaggenlijst = null;

JCombobox with actionperformed in another actionperformed

JCombobox with actionperformed in another actionperformed

java

jcombobox