當我改變它的顏色時，JButton不會改變顏色

Question

我有一排按鈕，它們都具有相同的顏色，綠色，除了「selectedButton」，它是橙色的。當我點擊一個按鈕時，它變成了新選定的按鈕，所以它變成橙色，其他所有變成綠色。我的代碼正確地將新的JButton更改爲橙色，但不會將前一個從橙色更改爲綠色。

如果我在paintComponent（）方法中調用revalidate（）和repaint（），它可以很好地工作，但是由於repaint（）方法只是再次調用paintComponent（）方法，所以有些東西告訴我這是個糟糕的主意，可能會以某種無限的遞歸結束，但我還沒有到目前爲止，我不知道爲什麼。我相信，revalidate（）和repaint（）將解決問題，如果放在我的代碼中的最佳位置，但我應該在哪裏添加它們。在修改mouseReleased（）事件上按鈕的顏色後，我厭倦了添加兩者，但它不起作用。

class StudentButton extends JButton{ 
    private int index; 
    private Color startGradient, endGradient; //Used for colouring JButton 
    private static StudentButton selectedButton; 

    public StudentButton(int i, boolean isSelected) { this("", i, isSelected); } 
    public StudentButton(String text, int i, boolean isSelected){ 
     super(text); index = i; 
     if(isSelected) 
      StudentButton.setSelectedButton(this); 
      //Colour set to orange 
      startGradient = new Color(234, 249, 99); 
      endGradient = new Color(230, 252, 35); 
     } 
     else { 
      //Colour set to green 
      startGradient = new Color(159, 255, 76); 
      endGradient = new Color(101, 183, 29); 
     } 

     addMouseListener(new MouseListener() { 
      public void mouseEntered(MouseEvent e) {} 
      public void mouseExited(MouseEvent e) {} 

      //mouseReleased better than mouseClicked, since it always triggers for an attempted click 
      public void mouseReleased(MouseEvent e) { 
       StudentButton selButton = StudentButton.getSelectedButton(); 
       selButton.setColourGradients(new Color(159, 255, 76), new Color(101, 183, 29)); 

       StudentButton newSelButton = (StudentButton)(e.getSource()); 
       newSelButton.setColourGradients(new Color(234, 249, 99), new Color(230, 252, 35)); 
       StudentButton.setSelectedButton(newSelButton); 
       //////////////////////////////////////////////// 
       //////////////////////////////////////////////// 
       //////////////////////////////////////////////// 
       //tried adding revalidate() and repaint() here, wouldn't work 
       //////////////////////////////////////////////// 
       //////////////////////////////////////////////// 
       //////////////////////////////////////////////// 
      } 
      public void mouseClicked(MouseEvent e) {} 
      public void mousePressed(MouseEvent e) {} 
     }); 

     setContentAreaFilled(false); ///removes ugly button border 
    } 

    public static StudentButton getSelectedButton() { return selectedButton; } 
    public static void setSelectedButton(StudentButton sb) { selectedButton = sb; } 

    public void setColourGradients(Color start, Color end) { 
     startGradient = start; endGradient = end; 
     System.out.println("Button "+index+", set to colour"+start); 
    } 
    protected void paintComponent(Graphics g) { 
     Graphics2D g2 = (Graphics2D) g; 

     GradientPaint p; 
     p = new GradientPaint(0, 0, startGradient, 
       0, getHeight(), endGradient); 

     g2.setPaint(p); 
     g2.fillRect(0, 0, getWidth(), getHeight()); 
     g2.setPaint(g2.getPaint()); 
     //////////////////////////////////////////////// 
     //////////////////////////////////////////////// 
     //This makes the buttons change correctly, but seems like a very bad idea     
     revalidate(); repaint(); 
     //////////////////////////////////////////////// 
     //////////////////////////////////////////////// 
     //////////////////////////////////////////////// 

     super.paintComponent(g); 
    } 

    public int getIndex() {return index;} 
} 

Answer 1

感謝@Bo_Halim我已經意識到我打電話重繪（），並重新驗證（）單StudentButton對象，而不是都該是在的mouseReleased（）方法改變的。我更改了mousePressed方法，以便重新繪製舊的選定按鈕和新選定的按鈕。

  public void mousePressed(MouseEvent e) { 
       StudentButton selButton = StudentButton.getSelectedButton(); 
       selButton.setColourGradients(new Color(159, 255, 76), new Color(101, 183, 29)); 
       selButton.revalidate(); selButton.repaint(); 

       StudentButton newSelButton = (StudentButton)(e.getSource()); 
       newSelButton.setColourGradients(new Color(234, 249, 99), new Color(230, 252, 35)); 
       StudentButton.setSelectedButton(newSelButton); 
       newSelButton.revalidate(); newSelButton.repaint(); 
      }