未显示的 Swing 组件

Question

这是我的代码，当我执行时，我得到的只是一个空白窗口。首先，当我尝试做main.setContentPane() 时，我得到了这个错误：

“无法对非静态字段面板进行静态引用”

所以我把它放在构造函数中，但什么都不会显示。

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class MainFrame extends JFrame{
    private JPanel panel;
    private JButton performance;
    private JButton concordance;
    private JButton discordance;
    private JButton resultat;

    public void MainFrame() {
        panel = new JPanel(new GridLayout(4, 1, 10, 10));
        performance = new JButton("performance");
        concordance = new JButton("concordance");
        discordance = new JButton("discordance");
        resultat = new JButton("resultat");

        performance.setSize(50, 30);
        concordance.setSize(50, 30);
        discordance.setSize(50, 30);
        resultat.setSize(50, 30);

        panel.add(performance);
        panel.add(concordance);
        panel.add(discordance);
        panel.add(resultat);
        getContentPane().add(panel);

    }
    public static void main(String[] args) {
        MainFrame main = new MainFrame();
        main.setSize(300, 200);
        main.setDefaultCloseOperation(EXIT_ON_CLOSE);
        main.setVisible(true);
    }
}

Answer 1

您有一个从未被调用过的名为 MainFrame 的方法（返回 void）。

您应该将其设为构造函数，或者创建一个调用该方法的构造函数，如下所示：

public class MainFrame extends JFrame {
  private JPanel panel;
  private JButton performance;
  private JButton concordance;
  private JButton discordance;
  private JButton resultat;

  public MainFrame() {
    super();
    MainFrame();
  }

  public void MainFrame() {
    panel = new JPanel(new GridLayout(4, 1, 10, 10));
    performance = new JButton("performance");
    concordance = new JButton("concordance");
    discordance = new JButton("discordance");
    resultat = new JButton("resultat");

    performance.setSize(50, 30);
    concordance.setSize(50, 30);
    discordance.setSize(50, 30);
    resultat.setSize(50, 30);

    panel.add(performance);
    panel.add(concordance);
    panel.add(discordance);
    panel.add(resultat);
    this.getContentPane().add(panel);

  }

  public static void main(String[] args) {
    MainFrame main = new MainFrame();
    main.setSize(300, 200);
    main.setDefaultCloseOperation(EXIT_ON_CLOSE);
    main.setVisible(true);
    main.MainFrame();
  }
}