如何通过单击JButton添加JPanel？

2 回答

• 8

  为了在添加/删除或调整可见容器上的组件后反映更改，在添加/删除或调整组件大小后，在容器实例上调用 revalidate() 和 repaint() .

  虽然这在你的代码中不起作用，但主要的原因是在JButton类中重新创建 MainPanel 的新实例，而实际上2 JButtons 应该共享正在使用的单个实例（你可以将MainPanel实例传递给 JButton 的构造函数，但是除非添加自定义功能，否则你不应该真正扩展 JButton ：

  class Button2 extends JButton {
      MainPanel someObj2 = new MainPanel();//you create an instance of MainPanel which isnt even showing and than do changes on that, this way you will never see any of the changes
  
      Button2() {
      }
  }
  

  关于您的代码的一些其他建议：

  • 不要不必要地扩展 JButton 类，只需创建 JButton 的实例，就像使用 JFrame 一样，并在 JButton 实例上调用方法 .

  • 别忘了在 Event Dispatch Thread 上创建/操作Swing组件，通过 SwingUtilities.invokeLater(..) 块，阅读here了解更多信息 .

  以下是您修复的代码（以上建议已实施）：

  import java.awt.Color;
  import java.awt.Dimension;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  import javax.swing.JButton;
  import javax.swing.JFrame;
  import javax.swing.JPanel;
  import javax.swing.SwingUtilities;
  
  public class Test {
  
      public static void main(String[] args) {
          SwingUtilities.invokeLater(new Runnable() {
              @Override
              public void run() {
                  JFrame f = new JFrame();
  
                  final MainPanel myPanel = new MainPanel();
                  f.add(myPanel);
  
                  JButton button1 = new JButton("Show Animation A");
                  JButton button2 = new JButton("Show Animation B");
  
                  button1.addActionListener(new ActionListener() {
                      @Override
                      public void actionPerformed(ActionEvent e) {
                          myPanel.setI(1);
                          System.out.println("The variable i is now: " + myPanel.i);
                          myPanel.refreshMe();
                      }
                  });
                  button2.addActionListener(new ActionListener() {
                      @Override
                      public void actionPerformed(ActionEvent e) {
                          myPanel.setI(2);
                          System.out.println("The variable i is now: " + myPanel.i);
                          myPanel.refreshMe();
                      }
                  });
  
                  myPanel.add(button1);
                  myPanel.add(button2);
                  myPanel.checkPanel();
  
                  f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
                  f.pack();
                  f.setVisible(true);
              }
          });
      }
  }
  
  class MainPanel extends JPanel {
  
      Panel1 p1 = new Panel1();
      Panel2 p2 = new Panel2();
      public int i = 1;  //this is being changed later by clicking JButton
      // I use this setter later in actionPerformed in order to change i
  
      public void setI(int i) {
          this.i = i;
      }
  
      public void refreshMe() {
          checkPanel();
  
          revalidate();
          repaint();
          // Need some help here:
          // I don't know what should I write, how to make a repaint of myPanel?
          System.out.println("just test, if the method refreshMe working by clicking some button");
      }
  
      public void checkPanel() {
          if (i == 1) {
              this.add(p1);
              this.remove(p2);//or it will remain there as this is default flowlayout
          } else if (i == 2) {
              this.add(p2);
              this.remove(p1);
          }
      }
  }
  
  class Panel1 extends JPanel {
  
      public Panel1() {
          this.setBackground(Color.BLUE);
          // a lot of drawing stuff going on here
      }
  
      @Override
      public Dimension getPreferredSize() {
          return new Dimension(200, 200);
      }
  }
  
  class Panel2 extends JPanel {
  
      public Panel2() {
          this.setBackground(Color.GREEN);
          // a lot of drawing stuff going on here
      }
  
      @Override
      public Dimension getPreferredSize() {
          return new Dimension(200, 200);
      }
  }
  

  但是，我建议更简单，幸运的是你有两个选择：

  1）使用CardLayout，它允许您在单个 JFrame /容器上的多个组件之间进行切换 .

  这是我做的一个例子：

  

  import java.awt.BorderLayout;
  import java.awt.CardLayout;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  import javax.swing.JButton;
  import javax.swing.JFrame;
  import javax.swing.JLabel;
  import javax.swing.JPanel;
  import javax.swing.SwingUtilities;
  
  public class Test {
  
      private final static String PANEL1 = "panel 1";
      private final static String PANEL2 = "panel 2";
  
      public Test() {
          initComponents();
      }
  
      public static void main(String[] args) {
          SwingUtilities.invokeLater(new Runnable() {
              @Override
              public void run() {
                  new Test();
              }
          });
      }
  
      private void initComponents() {
          JFrame frame = new JFrame();
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
          JPanel panel1 = new JPanel();
          panel1.add(new JLabel("Panel 1"));
  
          JPanel panel2 = new JPanel();
          panel2.add(new JLabel("Panel 2"));
  
          //Create the panel that contains the "cards".
          final JPanel cards = new JPanel(new CardLayout());
          cards.add(panel1, PANEL1);
          cards.add(panel2, PANEL2);
  
          //create button to allow chnage to next card
          JButton buttonNext = new JButton(">");
          buttonNext.addActionListener(new ActionListener() {
              @Override
              public void actionPerformed(ActionEvent ae) {
                  CardLayout cl = (CardLayout) (cards.getLayout());//get cards
                  cl.next(cards);
              }
          });
  
          //create button to allow chnage to previous card
          JButton buttonPrev = new JButton("<");
          buttonPrev.addActionListener(new ActionListener() {
              @Override
              public void actionPerformed(ActionEvent ae) {
                  CardLayout cl = (CardLayout) (cards.getLayout());//get cards
                  cl.previous(cards);
              }
          });
  
          //create panel to hold buttons which will allow switching between cards
          JPanel buttonPanel = new JPanel();
          buttonPanel.add(buttonPrev);
          buttonPanel.add(buttonNext);
  
  
          frame.add(cards);
          frame.add(buttonPanel, BorderLayout.SOUTH);
  
          frame.pack();
          frame.setVisible(true);
      }
  }
  

  2）使用 removeAll() 技术，即调用 frame.getContentPane().removeAll() ，这将删除当前在 JFrame 上的所有组件，然后添加新内容并在 JFrame 实例上调用 revalidate() 和 repaint() （也可能想在其中添加 pack() ）以反映更改 . 虽然我推荐 CardLayout .

  回复于 2024-04-28T07:15:45+08:00
• 3

  我想你可以使用 CardLayout 来实现你的功能 . 请参考here

  回复于 2024-04-28T07:15:45+08:00