动态添加的 JPanel 未显示在 Swing 中

Question

这是我的代码。显示以前设计的框架（添加了面板）时我没有任何问题。动态将面板添加到空 JFrame 时遇到此问题。

package com.mytunes.controllers;

import com.mytunes.views.*;
import com.mytunes.views.panels.*;
import java.awt.BorderLayout;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.WindowConstants;


public class GUIController {
    ArrayList<JFrame> displayFrames = new ArrayList<JFrame>();

    JPanel displayPanel;
    HeaderPanel headerPanel = new HeaderPanel();
    FooterPanel footerPanel = new FooterPanel();


    public int showFrame(String frameName, Object controller){
        Class c;
        Constructor ctr;
        int lastFrame = -1;

        try {

           // call a class dynamically
           c = Class.forName("com.mytunes.views.frames." + frameName + "Frame");
           // calll a constructor of a class
           ctr = c.getConstructor(SessionController.class);
           // instantiate dynamically created class
           displayFrames.add((JFrame) ctr.newInstance(controller));

           // get the index of frame just added
           lastFrame = displayFrames.size()-1;

           displayFrames.get(lastFrame).setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
           displayFrames.get(lastFrame).pack();
           displayFrames.get(lastFrame).setLocationRelativeTo(null);

           // hide it by default. 
           displayFrames.get(displayFrames.size()-1).setVisible(false);

        } catch (InstantiationException ex) {
            Logger.getLogger(GUIController.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            Logger.getLogger(GUIController.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IllegalArgumentException ex) {
            Logger.getLogger(GUIController.class.getName()).log(Level.SEVERE, null, ex);
        } catch (InvocationTargetException ex) {
            Logger.getLogger(GUIController.class.getName()).log(Level.SEVERE, null, ex);
        } catch (NoSuchMethodException ex) {
            Logger.getLogger(GUIController.class.getName()).log(Level.SEVERE, null, ex);
        } catch (SecurityException ex) {
            Logger.getLogger(GUIController.class.getName()).log(Level.SEVERE, null, ex);
        } catch (ClassNotFoundException ex) {
            JOptionPane.showMessageDialog(null, "Error while loading class 'com.mytunes.view.frames." + frameName + "'" );
        }

        System.out.println(lastFrame);
        return lastFrame;

    }

    //-------------show panels --------------//
     public void showOperator(String frame, Object controller){

        // this works fine! this frame is already having Panels
        int f = showFrame(frame, controller);
        displayFrames.get(f).setVisible(true);
     }
    public void showEnterPIN(String frame, Object controller){


        int f = showFrame(frame, controller);
        displayFrames.get(f).getContentPane().add(new EnterPINPanel(), BorderLayout.CENTER);
        displayFrames.get(f).setVisible(true);

        //        Try every following ways to show the "Dynamically added" panels
        //        displayFrames.get(f).getContentPane().removeAll();
        //        displayFrames.get(f).getContentPane().invalidate();
        //        displayFrames.get(f).getContentPane().add(new EnterPINPanel(), BorderLayout.PAGE_START);
        //        displayFrames.get(f).getContentPane().validate();
        //        displayFrames.get(f).pack();
        //        displayFrames.get(f).setVisible(true);

    }

}

如果有人能为我解决这个问题，我将不胜感激。谢谢。

Answer 1

如果将组件添加到容器中，则需要告诉容器的布局管理器通过调用 revalidate() 以及有时调用 repaint(); 来布局它们包含的所有组件> 在容器上。所以，就像...

JPanel contentPane = (JPanel)displayFrames.get(f).getContentPane();
contentPane.add(new EnterPINPanel(), BorderLayout.CENTER);
contentPane.revalidate();
contentPane.repaint();

话虽如此，您的应用程序设计看起来有点不同。您真的使用 JFrame 的 ArrayList 吗？大多数现实世界的应用程序不使用一堆单独的窗口，而是在一个主窗口中交换显示，您可以通过仅使用一个 JFrame 并通过 CardLayout 交换视图来使用 Swing 执行类似的操作。

编辑2
如果您尝试怎么办：

  int f = showFrame(frame, controller);
  JPanel contentPane = (JPanel)displayFrames.get(f).getContentPane();
  contentPane.removeAll();
  contentPane.setLayout(new BorderLayout()); // just to be sure
  contentPane.add(headerPanel, BorderLayout.PAGE_START);
  contentPane.add(new EnterPINPanel(), BorderLayout.CENTER);
  contentPane.add(footerPanel, BorderLayout.PAGE_END);
  contentPane.revalidate(); // *** note that it's **re**validate
  contentPane.repaint();
  displayFrames.get(f).setVisible(true);

同样，如果这没有帮助，那么您应该创建并发布“简短、独立、正确（可编译） )，示例”或 SSCCE

Answer 2

这可行

    JFrame contentPane = new JFrame();     
    contentPane.getContentPane().add(new EnterPINPanel(), BorderLayout.CENTER);
    contentPane.setVisible(true);

但不是这个

int f = <ArrayList index of last inserted Frame>
displayFrames.get(f).getContentPane().add(headerPanel, BorderLayout.PAGE_START);
displayFrames.get(f).getContentPane().add(new EnterPINPanel(), BorderLayout.CENTER);
displayFrames.get(f).getContentPane().add(footerPanel, BorderLayout.PAGE_END);
displayFrames.get(f).getContentPane().validate();
displayFrames.get(f).getContentPane().repaint();
displayFrames.get(f).setVisible(true);