常用的幾種監聽器

1.鍵盤監聽器：

class KeyFrame extends Frame {
    public KeyFrame() {
        setBounds(1,2,300,400);
        setVisible(true);
        
        this.addKeyListener(new KeyAdapter() {
            //鍵盤按下
            public void keyPressed(KeyEvent e) {
                int keyCode = e.getKeyCode();
                if (keyCode == KeyEvent.VK_UP) {
                    System.out.println("按了上鍵");
                }
            }
        });
    }

 

2.鼠標監聽器：

//適配器模式
    private class MyMouseListener extends MouseAdapter{
        public void mousePressed(MouseEvent e) {
            MyFrame frame = (MyFrame)e.getSource();
            //鼠標點擊時，將會在界面上產生一個點
            //這個點就是鼠標的點
            frame.addPoint(new Point(e.getX(),e.getY()));
            
            //每次點擊鼠標都重新畫一遍
            frame.repaint();
        }
    }

通過鼠標監聽器實現畫筆的功能：

class MyFrame extends Frame{
    ArrayList points;
    //需要畫筆，需要監聽鼠標當前的位置，需要集合存儲這個點
    public MyFrame(String title) {
        super(title);
        setBounds(200,200,400,300);
        setVisible(true);
        //存鼠標點擊的點
        points = new ArrayList<>();
        //添加一個鼠標監聽器
        this.addMouseListener(new MyMouseListener());
    }
    
    public void paint(Graphics g) {
        //畫畫，監聽鼠標的事件
        Iterator iterator = points.iterator();
        while (iterator.hasNext()) {
            Point point = (Point) iterator.next();
            g.setColor(Color.BLUE);
            g.fillOval(point.x, point.y, 10, 10);
        }
    }
    
    //添加一個點到界面上
    public void addPoint(Point point) {
        points.add(point);
    }
    
    //適配器模式
    private class MyMouseListener extends MouseAdapter{
        public void mousePressed(MouseEvent e) {
            MyFrame frame = (MyFrame)e.getSource();
            //鼠標點擊時，將會在界面上產生一個點
            //這個點就是鼠標的點
            frame.addPoint(new Point(e.getX(),e.getY()));
            
            //每次點擊鼠標都重新畫一遍
            frame.repaint();
        }
    }
}

 

3.窗口監聽器：

class MyWindowListener extends WindowAdapter {
        public void windowClosing(WindowEvent e) {
            setVisible(false);
            System.exit(0);
        }
        
    }

實例使用：

class WindowFrame extends Frame{
    public WindowFrame() {
        setBackground(Color.blue);
        setBounds(100,100,200,200);
        setVisible(true);
        addWindowListener(new MyWindowListener() {
            public void windowClosing(WindowEvent e) {
                setVisible(false);
            }
            
            public void windowActiated(WindowEvent e) {
                System.out.println("windowActivated");
            }
        });
    }
    
    class MyWindowListener extends WindowAdapter {
        public void windowClosing(WindowEvent e) {
            setVisible(false);
            System.exit(0);
        }
        
    }
}