JComboBox的ActionListener并初始化JPanel

Question

感谢JComboBox，我想编写一个可以在其中遇到场景（JPanel）的程序。 我用了ActionListener，但是没用

在构造函数的开头我将面板定义为final，但没有帮助。

scene.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        String choice = String.valueOf(scene.getSelectedItem());
        if(choice=="Sceneria"||choice=="Scene"){
            slider.setEnabled(false);
            panel = new JPanel();// problem here
        }
    }
});

错误

The final local variable panel cannot be assigned, since it is defined in an enclosing type

Answer 1

我建议您将 panel 设为 class 的属性。 然后调用panel如YourClass.this.panel.

public class YourClass {

    private JPanel panel;

    public YourClass() {

        // ...

        scene.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String choice = String.valueOf(scene.getSelectedItem());
                if(choice.equals("Sceneria") || choice.equals("Scene")) {
                    slider.setEnabled(false);
                    YourClass.this.panel = new JPanel();
                    YourClass.this.panel.revalidate();
                    YourClass.this.panel.repaint();
                }
            }
        });
    }
}