使用数组按下按钮时更改JButton图像

Question

我的actionPerformed方法有问题。每次按下按钮时，我都想更改按钮图像。如果我这样做了一个按钮（button[0][0]例如）它的工作原理，但我得到了

java.lang.ArrayIndexOutOfBoundsException

我被困在这里，我不知道如何解决问题...

public class ExButtons { 


JButton[][] button = new JButton[4][5]; 
ImageIcon[][] img = new ImageIcon[4][5]; 
ImageIcon cardTurned = new ImageIcon(); 

private final JPanel panel = new JPanel(); 
private final JFrame frame = new JFrame(); 
private int i, j; 

public ExButtons() { 

    img[0][0] = new ImageIcon("..."); 
    img[0][1] = new ImageIcon("..."); 
    img[0][2] = new ImageIcon("..."); 
    img[0][3] = new ImageIcon("..."); 
    img[0][4] = new ImageIcon("..."); 
    img[1][0] = new ImageIcon("..."); 
    img[1][1] = new ImageIcon("..."); 
    img[1][2] = new ImageIcon("..."); 
    img[1][3] = new ImageIcon("..."); 
    img[1][4] = new ImageIcon("..."); 
    img[2][0] = new ImageIcon("..."); 
    img[2][1] = new ImageIcon("..."); 
    img[2][2] = new ImageIcon("..."); 
    img[2][3] = new ImageIcon("..."); 
    img[2][4] = new ImageIcon("..."); 
    img[3][0] = new ImageIcon("..."); 
    img[3][1] = new ImageIcon("..."); 
    img[3][2] = new ImageIcon("..."); 
    img[3][3] = new ImageIcon("..."); 
    img[3][4] = new ImageIcon("..."); 
    cardTurned = new ImageIcon("..."); 

    for (i = 0; i < button.length; i++) { 
     for (j = 0; j < button[0].length; j++) { 
      button[i][j] = new JButton(img[i][j]); 

     } 
    } 

    int x = 100, y = 100; 

    for (i = 0; i < button.length; i++) { 
     for (j = 0; j < button[0].length; j++) { 

      button[i][j].setBounds(x, y, 60, 60); 
      panel.add(button[i][j]); 

      x += 80; 

      if (j == 4) { 

       x = 100; 
       y += 80; 
      } 
     } 
    } 

    for (i = 0; i < button.length; i++) { 
     for (j = 0; j < button[0].length; j++) { 

      button[i][j].addActionListener(new ActionListener() { 

       @Override 
       public void actionPerformed(ActionEvent e) { 

        System.out.println("Button[" + i + "][" + j + "] was pressed"); 
        button[i][j].setIcon(button[i][j].getIcon() == img[i][j] ? cardTurned : img[i][j]); 

       } 
      }); 
     } 
    } 

    frame.setSize(600, 600); 
    frame.setLocationRelativeTo(null); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    panel.setLayout(null); 
    for (i = 0; i < button.length; i++) { 
     for (j = 0; j < button[0].length; j++) { 
      panel.add(button[i][j]); 
     } 
    } 

    frame.add(panel); 
    frame.setVisible(true); 

} 

public static void main(String[] args) { 
    new ExButtons().frame.setVisible(true); 
} 
} 

Answer 1

在循环结束时，i和j都出界了。所以你所有的听众对我和j使用这些出界值。

我和j不应该是字段。它们应该是局部变量。而且，由于听众需要最后的变量，你需要这些变量的最终副本：

for (int i = 0; i < button.length; i++) { 
    for (int j = 0; j < button[0].length; j++) { 

     final int i2 = i; 
     final int j2 = j; 

     button[i][j].addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 

       System.out.println("Button[" + i2 + "][" + j2 + "] was pressed"); 
       button[i2][j2].setIcon(button[i2][j2].getIcon() == img[i2][j2] ? cardTurned : img[i2][j2]); 

      } 
     }); 
    } 
} 

或者简单：

for (int i = 0; i < button.length; i++) { 
    for (int j = 0; j < button[0].length; j++) { 

     final JButton btn = button[i][j]; 
     final ImageIcon image = img[i][j]; 

     btn.addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 

       btn.setIcon(btn.getIcon() == image ? cardTurned : image); 

      } 
     }); 
    } 
} 

你也一定要抛弃你设定按钮的界限的想法。改用布局管理器。这是它的工作。