Question

您好，我有3个单独的类，一个用于框架，一个用于面板，一个用于keyListener

每当我按左键箭头时，我都希望它在框架上打印一些东西。我已经使用过getGraphics（），但是我已经读过它是不好的作法，而且我不确定如何正确地做到这一点。我阅读了有关以下内容的教程：https://docs.oracle.com/javase/tutorial/uiswing/painting/index.html

“ paintComponent方法是所有自定义绘画所用的地方地点。该方法由javax.swing.JComponent定义，然后由您的子类重写以提供其自定义行为。”

因此，我尝试在KeyboardListener中扩展DrawingBoard类但是在keyPressed方法中，我不知道如何调用paintCompoment（Graphics g）作为参数放置什么，这是正确的方法吗？

    public class Main {

        public static void main(String[] args) {

            SwingUtilities.invokeLater(new UserInterface());
        }
    }

    public class UserInterface implements Runnable {

        private JFrame frame;
        private DrawingBoard drawingBoard;

        @Override
        public void run() {
            // TODO Auto-generated method stub
            frame = new JFrame("");
            frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            createComponents(frame.getContentPane());
            addListener();
            frame.pack();
            frame.setVisible(true);

        }

        public void createComponents(Container container) {
            drawingBoard = new DrawingBoard();
            container.add(drawingBoard);
        }

        public void addListener() {
            frame.addKeyListener(new KeyboardListener(drawingBoard));
        }

    }

    public class DrawingBoard extends JPanel {

        public Dimension getPreferredSize() {
            return new Dimension(250, 200);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

        }

    }

public class KeyboardListener extends DrawingBoard implements KeyListener {

    private DrawingBoard drawingBoard;

    public KeyboardListener(DrawingBoard drawingBoard) {
        this.drawingBoard = drawingBoard;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawString("Hello", 50, 50);

    }

    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_LEFT) {
            // How do I call paintComponent
            // What do I put as a parameter ?
        }

    }

    @Override
    public void keyReleased(KeyEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void keyTyped(KeyEvent e) {
        // TODO Auto-generated method stub
    }
}

如何在不使用GetGraphics（）的情况下从KeyPressed绘制内容

0 个答案: