使用 Java Swing 进行双缓冲留下痕迹

Question

我正在从事的项目旨在展示一个.gif带有背景的可移动物体。目前，如果我使用的super.paint(g);话，角色和背景画就会闪烁。如果我不这样做，那么它会留下像所包含的图像一样的痕迹。我不知道为什么会发生这种情况，需要帮助。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Image;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.border.EmptyBorder;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JLabel;

public class keyboardinput extends JFrame implements ActionListener, KeyListener {
    private JPanel contentPane;

    private Image playerModelRight;
    private Image playerModelLeft;
    private Image playerModelAttackRight;
    private Image playerModelAttackLeft;
    private Image playerModelStandRight;
    private Image playerModelStandLeft;
    private Image background;
    private Image doubleBuffer;

    private int direction;

    private Timer timer;

    private boolean up;
    private boolean down;
    private boolean left;
    private boolean right;
    private boolean attack;

    private int x, y;
    private int speed = 4;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    keyboardinput frame = new keyboardinput();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public keyboardinput() {

        super("Keyboard input testing");

        x = 200;
        y = 200;

        ImageIcon playerModelIconRight = new    ImageIcon(keyboardinput.class.getResource("/images/bitdashright.gif"));
        playerModelRight = playerModelIconRight.getImage();

        ImageIcon playerModelIconLeft = new ImageIcon(keyboardinput.class.getResource("/images/bitdashleft.gif"));
        playerModelLeft = playerModelIconLeft.getImage();

        ImageIcon playerModelIconStandRight = new ImageIcon(keyboardinput.class.getResource("/images/bitdashstandright.gif"));
        playerModelStandRight = playerModelIconStandRight.getImage();

        ImageIcon playerModelIconStandLeft = new ImageIcon(keyboardinput.class.getResource("/images/bitdashstandleft.gif"));
        playerModelStandLeft = playerModelIconStandLeft.getImage();

        ImageIcon playerModelIconAttackRight = new ImageIcon(keyboardinput.class.getResource("/images/bitdashattackright.gif"));
        playerModelAttackRight = playerModelIconAttackRight.getImage();

        ImageIcon playerModelIconAttackLeft = new ImageIcon(keyboardinput.class.getResource("/images/bitdashattackleft.gif"));
        playerModelAttackLeft = playerModelIconAttackLeft.getImage();

        ImageIcon backgroundIcon = new ImageIcon(keyboardinput.class.getResource("/images/backgroundtest.png"));
        background = backgroundIcon.getImage();

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(50, 50, 800, 500);
        contentPane = new JPanel();

        addKeyListener(this);

        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        timer = new Timer(10, this);
        timer.start();
    }

    public void update(Graphics g) {
        Dimension size = getSize();
        if (doubleBuffer == null || doubleBuffer.getWidth(this) != size.width || doubleBuffer.getHeight(this) != size.height) {
            doubleBuffer = createImage(size.width, size.height);
        }

        if (doubleBuffer != null) {
            Graphics g2 = doubleBuffer.getGraphics();
            paint(g2);
            g2.dispose();

            g.drawImage(doubleBuffer, 0, 0, null);
        } else {
            paint(g);
        }
    }

    public void paint(Graphics g) {
        super.paintComponents(g);
        if (attack) {
            if (direction == 1)
                g.drawImage(playerModelAttackRight, x, y, this);
            if (direction == 0) {
                x -= 15;
                g.drawImage(playerModelAttackLeft, x, y, this);
                x += 15;
            }
        } else if (left && right)
            g.drawImage(playerModelStandRight, x, y, this);
        else if (right)
            g.drawImage(playerModelRight, x, y, this);
        else if (left)
            g.drawImage(playerModelLeft, x, y, this);
        else {
            if (direction == 1)
                g.drawImage(playerModelStandRight, x, y, this);
            if (direction == 0)
                g.drawImage(playerModelStandLeft, x, y, this);
        }
        // g.drawImage(background, 0, 0, this);

    }

    public void actionPerformed(ActionEvent arg0) {
        if (attack)
            return;
        if (up && y > 235)
            y -= speed;
        if (down && y < 430)
            y += speed;
        if (left && x > -10)
            x -= speed;
        if (right && x < 750)
            x += speed;
        repaint();
        System.out.println(x + ", " + y);
    }

    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
            right = true;
            direction = 1;
        }
        if (e.getKeyCode() == KeyEvent.VK_LEFT) {
            left = true;
            direction = 0;
        }
        if (e.getKeyCode() == KeyEvent.VK_DOWN)
            down = true;
        if (e.getKeyCode() == KeyEvent.VK_UP)
            up = true;
        if (e.getKeyCode() == KeyEvent.VK_SPACE)
            attack = true;

    }

    public void keyReleased(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_RIGHT)
            right = false;
        if (e.getKeyCode() == KeyEvent.VK_LEFT)
            left = false;
        if (e.getKeyCode() == KeyEvent.VK_DOWN)
            down = false;
        if (e.getKeyCode() == KeyEvent.VK_UP)
            up = false;
        if (e.getKeyCode() == KeyEvent.VK_SPACE)
            attack = false;
    }

    public void keyTyped(KeyEvent arg0) {
        // TODO Auto-generated method stub

    }

}

Answer 1

public void paint(Graphics g) {
    super.paintComponents(g);

1. 这肯定会带来麻烦。不要在重写中调用错误的超级方法。
2. 不要直接在 JFrame 中绘制，而是在 JPanel 的 PaintComponent 方法中绘制。
3. 不要update在 Swing 程序中重写。

请查看教程：

• 课程：执行自定义绘画：Swing 图形入门教程
• 在 AWT 和 Swing 中绘画：Swing 图形高级教程