從ActionListener調用方法

Question

我想要一個按鈕，當按下該按鈕時，將調用一個方法。 這是一些代碼

public class Tester extends JPanel {              
    public void paintComponent(Graphics g){
        super.paintComponent(g);            
        g.fillRect(10, 10, 10, 10);

    }
    //The method which I wand invoke but can't, I don't know why.
    void setWidth(){
        //width -= 10 ;
        repaint();
    }

    public static void main(String[] args) {
            //Here some JFrame...
            Tester paint = new Tester();
            frame.add(paint);
            JButton click = new JButton("Click");

            click.addActionListener(new ActionListener(){

                @Override
                public void actionPerformed(ActionEvent e) {
                    paint.setWidth();//Here I Want invoke that method
                }

            });
    }
}

我希望ActionListener會調用方法setWidth() ，但不會。 不知道為什么。

Answer 1

paint變量不在匿名ActionListener類的范圍內，請嘗試更改paint類以使其實現ActionListener接口，並使其實例成為“ Click”按鈕的動作偵聽器，還應將該按鈕附加到面板實例上，如下所示：

public class Tester extends JPanel implements ActionListener {              

   @Override
   public void actionPerformed(ActionEvent e) {
         setWidth();
   }

    public static void main(String[] args) {
            //Here some JFrame...
            Tester paint = new Tester();            
            frame.add(paint);

            JButton click = new JButton("Click");
            paint.add(click);
            click.addActionListener(paint);

    }
}