当 JPanel 更改时，旧 JPanel 的元素会被留下

Question

我正在使用 JTabbedPane，每个选项卡上都有一个面板，当用户执行单击按钮等操作时，该面板会发生变化。我遇到的问题是前一个面板中的元素被遗漏了。通常，只有将鼠标移到它们上方，您才能看到它们，但有时，只有将鼠标移到它们应该出现的位置，才能看到新面板的元素。是。因此，通常一开始只有一点点可见，然后：

当您将鼠标移到更多内容上时，它就会变得可见< /a>

然后由于某种原因，当您点击“多项选择”时，应该创建四个新按钮，一切都变得完美可见。

我已经得到了 repaint(); ，就像几乎所有其他行一样，在我更改 GUI 上的任何内容之前，我首先执行 removeAll(); ，但这一切都在不断发生后退！有什么建议吗？该面板的代码如下，如果有帮助的话......

package com.GC01.gui;

import java.awt.Color;

public class PracticeQuizPanel extends JPanel implements MouseListener {
    /**
     * This panel will allow the user to practice quiz questions.
     */
private static final long serialVersionUID = 1L;

private User user = new User("misha");

boolean isMultipleChoice=false;
boolean usedClue=false;
boolean isStarted=false;

Calendar calendar = Calendar.getInstance();
AnswerAnalysis aA = new AnswerAnalysis();   
private Quiz qz = new Quiz( Quiz.getQuestionsFromDisk(), 4, TabbedQuiz.getUser().getNumLogins() );

private JTextArea questionArea;
private JTextArea clueArea;
private JTextArea answerArea;

private JButton clueButton;
private JButton multiButton;
private JButton answerButton;
private JButton startButton; 

private int index=0;
private Calendar startCalendar, endCalendar;

private JPanel backPanel;

public PracticeQuizPanel(){
    add(new StartButtonPanel());
}

PracticeQuizPanel(int index) {
    createVisualElements(index);
}

public void offerAnswer(){
    endCalendar = Calendar.getInstance();
    aA.setTimeSpent((int) (endCalendar.getTimeInMillis()-startCalendar.getTimeInMillis()));
    aA.setRight(answerArea.getText());
    JOptionPane.showMessageDialog(null, aA.toString());
    answerArea.setEditable(false);
    qz.setAnswersAnalysis(index, aA);
    index++;
    removeAll(); 
    if( index<qz.getLength() ) createVisualElements(index);
    else {
        removeAll();
        JOptionPane.showMessageDialog(null, qz.toFriendlyString());
        addQuizResultsToUserProgress();
        JOptionPane.showMessageDialog(null, qz.toFriendlyString());
        UserProgress uP = new UserProgress(user);
        System.out.println(uP.toString());
    }
    repaint();
    startCalendar = Calendar.getInstance();
    //JOptionPane.showMessageDialog(null, isStarted);
}

public void addQuizResultsToUserProgress(){
    UserProgress userProgress = new UserProgress(user);
    ArrayList<AnswerAnalysis> asA = userProgress.getAnswersAnalysis();
    for (int i=0; i<qz.getLength(); i++){
        asA.add( qz.getAnswersAnalysis()[i]);
    }
    userProgress.setAnswersAnalysis(asA);
    userProgress.saveProgress();
}



/**
 * This method creates/recreates all the text boxes, buttons etc. without resetting the quiz and
 * the objects in memory.
 */
private void createVisualElements(int index){
    if (TabbedQuiz.getUser().getNumLogins()<0) 
        JOptionPane.showMessageDialog(null, "There was an error. You may have done this quiz before.");
    removeAll();
    repaint();
    startCalendar = Calendar.getInstance();
    this.index=index;
    setBackground(new Color(112, 128, 144)); 
    setBounds(0,0,728,380);
    setLayout(null);

    questionArea = new JTextArea();
    questionArea.setFont(TabbedQuiz.getDefaultFont().deriveFont(20));//new Font("Courier New", 0, 20));
    questionArea.setEditable(false);
    questionArea.setLineWrap(true);
    questionArea.setWrapStyleWord(true);
    questionArea.setBounds(295, 11, 423, 74);
    add(questionArea);
    //int index=0;
    Question q = qz.getQuestions().get(index);
    aA = new AnswerAnalysis(q.getQuestionID());
    questionArea.setText(q.getQuestionText() );

    clueArea = new JTextArea();
    clueArea.setFont(TabbedQuiz.getDefaultFont().deriveFont(20));
    clueArea.setEditable(false);
    clueArea.setLineWrap(true);
    clueArea.setWrapStyleWord(true);
    clueArea.setBounds(295, 104, 423, 55);
    add(clueArea);

    JLabel lblQuestion = new JLabel("QUESTION:");
    lblQuestion.setFont(TabbedQuiz.getDefaultFont().deriveFont(40));
    lblQuestion.setBounds(43, 11, 216, 61);
    add(lblQuestion);

    answerArea = new JTextArea();//index+"");
    answerArea.setFont(TabbedQuiz.getDefaultFont().deriveFont(20));
    answerArea.setLineWrap(true);
    answerArea.setWrapStyleWord(true);
    answerArea.setBounds(295, 301, 423, 50);
    answerArea.addKeyListener(new KeyAdapter() {
        @Override
        public void keyPressed(KeyEvent e) {
            if(e.getKeyCode() == KeyEvent.VK_ENTER) offerAnswer();
        }
    });

    add(answerArea);
    answerArea.setFocusable(true);
    answerArea.requestFocusInWindow();

    clueButton = new JButton("CLUE?");
    clueButton.setFont(TabbedQuiz.getDefaultFont().deriveFont(40));
    clueButton.addMouseListener(this);
    clueButton.setBounds(15, 104, 244, 55);
    add(clueButton);

    multiButton = new JButton("MULTIPLE CHOICE?");
    multiButton.setFont(TabbedQuiz.getDefaultFont().deriveFont(20));
    multiButton.addMouseListener(this);
    multiButton.setBounds(15, 195, 244, 55);
    add(multiButton);

    answerButton = new JButton("ANSWER!");
    answerButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
        }
    });
    answerButton.setFont(TabbedQuiz.getDefaultFont().deriveFont(40));
    answerButton.setBounds(15, 301, 244, 55);
    answerButton.addMouseListener(this);
    add(answerButton);

    backPanel = new JPanel();
    backPanel.setBounds(0, 0, 728, 380);
    //add(backPanel);

    this.setVisible(true);
    repaint();
}

@Override
public void mouseClicked(MouseEvent e) {
    if      ( e.getSource().equals(startButton)  ) {
        remove(startButton); repaint(); isStarted=true;
        startCalendar = Calendar.getInstance();
    }
    else if ( e.getSource().equals(answerButton) ) offerAnswer();
    else if ( e.getSource().equals(clueButton )  ) {
        clueArea.setText(clueArea.getText() + qz.getQuestions().get(index).getClueText() + "\n");
        aA.setUsedClue(true);
        //JOptionPane.showMessageDialog(null, "hi");
        }
    else if ( e.getSource().equals(multiButton)  ) {            
        String[] answerOptions = qz.getQuestions().get(index).getAnswerOptions(3);
        JButton[] optionsButtons = new JButton[4];
        for(int j=0;j<4;j++){
            optionsButtons[j]=new JButton(answerOptions[j]);
            if(optionsButtons[j].getText().length()>13) 
                optionsButtons[j].setFont(TabbedQuiz.getDefaultFont().deriveFont(10));
            else optionsButtons[j].setFont(TabbedQuiz.getDefaultFont().deriveFont(15));
            if(j<2) optionsButtons[j].setBounds(295+211*j       , 170, 211, 55);
            else    optionsButtons[j].setBounds(295+211*(j-2)   , 226, 211, 55);
            optionsButtons[j].addMouseListener(this);
            optionsButtons[j].setName("optionsButton"+"["+j+"]");
            add(optionsButtons[j]);
            repaint();
        }
        aA.setMultipleChoice(true);
    }
    else if ( ( (JButton) e.getSource() ).getName().startsWith("optionsButton") ) {
        String answerOffered = ( (JButton) e.getSource() ).getText();
        answerArea.setText(answerOffered);
        offerAnswer();
    }
}

@Override
public void mouseEntered(MouseEvent e) {
    if(e.getSource()!=startButton && e.getSource().getClass().equals( answerButton.getClass()) ){
        ( (JButton) e.getSource() ).setBackground(Color.green);
    }if(index>0 && e.getSource()==startButton) remove(startButton);
}

@Override
public void mouseExited(MouseEvent e) {
    if(e.getSource()!=startButton && e.getSource().getClass().equals( answerButton.getClass()) ){
        ( (JButton) e.getSource() ).setBackground(UIManager.getColor("control"));
    }
}

@Override
public void mousePressed(MouseEvent e) {
}

@Override
public void mouseReleased(MouseEvent e) {
}
}

Answer 1

每个选项卡上都有一个面板，当用户执行单击按钮等操作时，该面板会发生变化。

在我更改 GUI 上的任何内容之前，我会执行 removeAll();

每当我看到这样的评论时，我觉得你应该使用 卡片布局让您不必担心所有这些问题。

Answer 2

如果使用布局管理器，则需要在向容器中删除或添加组件后调用revalidate。然后调用repaint。

您发布了很多代码，其中大部分与当前的问题完全无关，但另一方面，发布的代码不完整，无法编译，因此不是我们可以测试的代码。请下次尽量不要发布大量与问题无关的代码。尝试通过不断删除代码来隔离问题，然后如果仍然卡住，发布一个最小的可编译程序，我们可以自己研究、测试、运行和修改，一个sscce。

我已经浏览了您的一些 GUI 代码（天哪，不是全部！），并且在您进行 Swing 绘画时存在一些严重的问题，例如来自 ProgressPanel.java 的这段代码：

   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      Graphics2D g2d = (Graphics2D) g;
      createAndShowGUI(g2d);
      // drawDifficultyChart(g2d, fontComboBox.getSelectedIndex());
   }

   private void createAndShowGUI(Graphics2D g2d) {
      JButton showChartButton = new JButton("Show new chart!");
      user = TabbedQuiz.getUser();
      showChartButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            try {
               if (categoryComboBox.getSelectedIndex() == 0
                     && difficultyComboBox.getSelectedIndex() != 0) {
                  drawDifficultyChart((Graphics2D) getGraphics(),
                        difficultyComboBox.getSelectedIndex());
               } else if (difficultyComboBox.getSelectedIndex() == 0
                     && categoryComboBox.getSelectedIndex() != 0) {
                  drawCategoryChart((Graphics2D) getGraphics(),
                        (String) categoryComboBox.getSelectedItem());
               } else
                  drawGeneralChart((Graphics2D) getGraphics(),
                        (String) categoryComboBox.getSelectedItem(),
                        difficultyComboBox.getSelectedIndex());
            } catch (NullPointerException e1) {
               JOptionPane.showMessageDialog(null, "Sign in first.");
            }
         }
      });
      showChartButton.setBounds(10, 90, 96, 26);
      showChartButton.setFont(font);
      add(showChartButton);
   }

问题是您'从 Paint/paintComponent 方法中创建组件并将其添加到容器中，这是您永远不应该做的事情，而且肯定会弄乱程序的图形。

Answer 3

对于遇到此问题的其他人：我最终解决了问题。 setVisible(假); setVisible(true);。把它放在任何地方。