在 actionlistener 中使用非局部变量

Question

我想在它的动作侦听器中使用一个变量。这是我的代码：

public class Face {

public Face(){

    Btn1 =  new JToggleButton();
    Btn2 =  new JToggleButton();
    Btn3 =  new JToggleButton();
    Btn4 =  new JToggleButton();
    Btn5 =  new JToggleButton();
    Btn6 =  new JToggleButton();

}


public Start6(){

    JToggleButton[] Btn = new javax.swing.JToggleButton[5]; // An array for saving address of all buttons

    Btn[0] = Btn1 ;
    Btn[1] = Btn2 ;
    Btn[2] = Btn3 ;
    Btn[3] = Btn4 ;
    Btn[4] = Btn5 ;
    Btn[5] = Btn6 ;

   for (int i = 0 ; i < 36 ; i++) {
        Btn[i].addActionListener(new ActionListener() {     
        @Override
        public void actionPerformed(ActionEvent e) {
        Btn[i].setSize(150, 150);
        ImageIcon BtnImage = new ImageIcon(getClass().getResource("/GameImages/" + /* a picture name*/ + ".jpg" ));
        Image img = BtnImage.getImage();
        Btn[i].setIcon( new ImageIcon(img.getScaledInstance(225,160 ,Image.SCALE_FAST)));
        X6P.add(Btn[i]);
        }
    });
    }


   }
  public javax.swing.JToggleButton Btn1;
  public javax.swing.JToggleButton Btn2;
  public javax.swing.JToggleButton Btn3;
  public javax.swing.JToggleButton Btn4;
  public javax.swing.JToggleButton Btn5;
  }

当我想在 Btn 数组（相同数组）的动作侦听器中使用 Btn 数组时，出现此错误：

local variables referenced from an inner class must be final or effectively final i want when button clicked show it's icon ...

Answer 1

错误的意思正是它所说的：您的数组变量 Btn 不是 final，因此无法从内部 class 访问它。使其成为 final 将解决问题：

final JToggleButton[] Btn = new ...

另一个解决方案是将数组移动到 class:

public javax.swing.JToggleButton Btn1;
public javax.swing.JToggleButton Btn2;
public javax.swing.JToggleButton Btn3;
public javax.swing.JToggleButton Btn4;
public javax.swing.JToggleButton Btn5;
private javax.swing.JToggleButton[] Btn = new javax.swing.JToggleButton[] {
    Btn1, Btn2, Btn3, Btn4, Btn5
};

这会做同样的事情，并使您的代码更短。

I want when button clicked show its icon

您根本不需要使用数组：与其引用 Btn[i]，不如引用 e.getSource()。它被设置为被点击的按钮 - 你需要做的就是施放它：

javax.swing.JToggleButton sender = (javax.swing.JToggleButton)e.getSource();

在循环外部创建一个动作侦听器，并将其设置在所有按钮上。这将完全消除数组：

// The same listener instance can handle all buttons
ActionListener actListener = new ActionListener() {     
    @Override
    public void actionPerformed(ActionEvent e) {
        javax.swing.JToggleButton senderButton = (javax.swing.JToggleButton)e.getSource();
        ... // Do anything you want with senderButton here
    }
};
// Add the same listener to all buttons
for (int i = 0 ; i < 36 ; i++) {
    Btn[i].addActionListener(actListener);
}

在 actionlistener 中使用非局部变量

Use non-local variables in actionlistener

java

icons

actionlistener