当我改变它的颜色时，JButton不会改变颜色

Question

我有一排按钮，它们都具有相同的颜色，绿色，除了“selectedButton”，它是橙色的。当我点击一个按钮时，它变成了新选定的按钮，所以它变成橙色，其他所有变成绿色。我的代码正确地将新的JButton更改为橙色，但不会将前一个从橙色更改为绿色。

如果我在paintComponent（）方法中调用revalidate（）和repaint（），它可以很好地工作，但是由于repaint（）方法只是再次调用paintComponent（）方法，所以有些东西告诉我这是个糟糕的主意，可能会以某种无限的递归结束，但我还没有到目前为止，我不知道为什么。我相信，revalidate（）和repaint（）将解决问题，如果放在我的代码中的最佳位置，但我应该在哪里添加它们。在修改mouseReleased（）事件上按钮的颜色后，我厌倦了添加两者，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

感谢@Bo_Halim我已经意识到我打电话重绘（），并重新验证（）单StudentButton对象，而不是都该是在的mouseReleased（）方法改变的。我更改了mousePressed方法，以便重新绘制旧的选定按钮和新选定的按钮。

  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(); 
      }