java - 如何防止闪烁？

Question

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Racing extends JFrame {
private static final long serialVersionUID = -198172151996959655L;

//makes the screen size
final int WIDTH = 900, HEIGHT = 650;

//keeps track of player speed
double plSpeed = .5;

//numbers that represent direction
final int UP = 0, RIGHT = 1, DOWN = 2, LEFT = 3, STOP = 5, START = 6;

//keeps track of player direction
int p1Direction = START;

//makes player 1's car
Rectangle p1 = new Rectangle ( 100, 325, 30, 30 );
Rectangle foreground = new Rectangle( 500, 500, 200, 200 );

//constructor
public Racing() {
    //define defaults for the JFrame
    super ("Racing");
    setSize( WIDTH, HEIGHT );
    setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    setBackground(Color.BLACK);

    //start the inner class
    Move1 m1 = new Move1();
    m1.start();
}

//draws the cars and race track
public void paint(Graphics g) {

    super.paint(g);
    //draw p1
    g.setColor(Color.RED);
    g.fillRect(p1.x,p1.y,p1.width,p1.height);
    g.setColor(Color.GREEN);
    g.fillRect(foreground.x,foreground.y,foreground.width,foreground.height);

}
private class Move1 extends Thread implements KeyListener {
    public void run() {
        //makes the key listener "wake up"
        addKeyListener(this);

        //should be done in an infinite loop, so it repeats
        while (true) {
            //make try block, so it can exit if it errors
            try {
                //refresh screen
                repaint();

                //makes car increase speed a bit
                if (plSpeed <= 7) {
                    plSpeed += .2;
                }

                //lets the car stop
                if (plSpeed==0) {
                    p1Direction = STOP;
                }

                //moves player based on direction
                if (p1Direction==UP) {
                    p1.y -= (int) plSpeed;
                }
                if (p1Direction==DOWN) {
                    p1.y += (int) plSpeed;
                }
                if (p1Direction==LEFT) {
                    p1.x -= (int) plSpeed;
                }
                if (p1Direction==RIGHT) {
                    p1.x += (int) plSpeed;
                }
                if (p1Direction==STOP) {
                    plSpeed = 0;
                }

                //delays refresh rate
                Thread.sleep(75);

            }
            catch(Exception e) {
                //if an error, exit
                break;
            }
        }
    }

    //have to input these (so it will compile)
    public void keyPressed(KeyEvent event) {
        try {
            //makes car increase speed a bit
            if (event.getKeyChar()=='w' ||
                event.getKeyChar()=='a' ||
                event.getKeyChar()=='s' ||
                event.getKeyChar()=='d') {
                    plSpeed += .2;
                    repaint();
            }
        } catch (Exception I) {}
    }
    public void keyReleased(KeyEvent event) {}

    //now, to be able to set the direction
    public void keyTyped(KeyEvent event) {
        if (plSpeed > 0) {
            if (event.getKeyChar()=='a') {
                if (p1Direction==RIGHT) {
                    p1Brake();
                } else {
                    if (p1Direction==LEFT) {
                    } else {
                        p1Direction = LEFT;
                    }
                }
            }
            if (event.getKeyChar()=='s') {
                if (p1Direction==UP) {
                    p1Brake();
                } else {
                    if (p1Direction==DOWN) {
                    } else {
                        p1Direction = DOWN;
                    }
                }
            }
            if (event.getKeyChar()=='d') {
                if (p1Direction==LEFT) {
                    p1Brake();
                } else {
                    if (p1Direction==RIGHT) {
                    } else {
                        p1Direction = RIGHT;
                    }
                }
            }
            if (event.getKeyChar()=='w') {
                if (p1Direction==DOWN) {
                    p1Brake();
                } else {
                    if (p1Direction==UP) {
                    } else {
                        p1Direction = UP;
                    }
                }
            }
            if (event.getKeyChar()=='z') {
                p1Brake();
            }
        }
    }

    public void p1Brake () {
        try {
            while (plSpeed != 0) {
                plSpeed -= .2;
                Thread.sleep(75);
            }
        } catch (Exception e) {
            plSpeed = 0;
        }
    }
}

//finally, to start the program
public static void main(String[] args) {
    Racing frame = new Racing();
    frame.setVisible( true );
    frame.setLocationRelativeTo( null );
    frame.setResizable( false );
}

这是我的代码的 SSCCE。如果我添加 super.paint(g);最重要的是，在类里面，一切都变得浮华。如果我不考虑它，那么每当你移动玩家时，它都会创建一条玩家去过的地方的线 - 无需重新绘制。我需要知道如何 - 以及在哪里重新粉刷。我在这里最接近我的答案:

http://www.java-forums.org/awt-swing/37406-repaint-without-flashing.html

但是他们有一个小程序(我以前从未处理过，并且假设将代码从小程序转换为框架会相当棘手)。有人可以帮我解决这个问题吗？

注意事项:

我不知道你可以用 awt 制作框架，因为我很高兴并且熟悉 swing，所以我不想改变。对于那个很抱歉。如您所见，无论我绘制什么都会闪烁，而不仅仅是播放器。

安德鲁，这是我的截图:

哦，它没有注册 P2。

Answer 1

我做了一些改变。以下是我能记忆起的一些内容。

1. 将自定义绘画从顶级容器重构到 JPanel，并将绘画移动到 paintComponent()。
2. 删除了 Thread 和 Thread.sleep(n) 并替换为 Timer/ActionListener。<
3. 在 EDT 上构建了 GUI。
4. 删除了设置 JFrame 的大小。而是为 JPanel(实际绘图区域)设置首选大小并调用 JFrame.pack() 以获得正确的整体大小。
5. 使用 setLocationByPlatform(true) 代替 very splash-screen like setLocationRelativeTo(null)。

仔细检查代码以获取更多提示。

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Racing extends JPanel implements KeyListener {
private static final long serialVersionUID = -198172151996959655L;

//keeps track of player speed
double plSpeed = .5;

//numbers that represent direction
final int UP = 0, RIGHT = 1, DOWN = 2, LEFT = 3, STOP = 5, START = 6;

//keeps track of player direction
int p1Direction = START;

//makes player 1's car
Rectangle p1 = new Rectangle ( 100, 25, 30, 30 );

//constructor
public Racing() {
    //define defaults for the JFrame
    setBackground(Color.BLACK);

    //makes the screen size
    setPreferredSize(new Dimension(400,50));

    //makes the key listener "wake up"
    addKeyListener(this);
    setFocusable(true);

    ActionListener al = new ActionListener() {
        public void actionPerformed(ActionEvent ae) {
            //refresh screen
            repaint();

            //makes car increase speed a bit
            if (plSpeed <= 7) {
                plSpeed += .2;
            }

            //lets the car stop
            if (plSpeed==0) {
                p1Direction = STOP;
            }

            //moves player based on direction
            if (p1Direction==UP) {
                p1.y -= (int) plSpeed;
            }
            if (p1Direction==DOWN) {
                p1.y += (int) plSpeed;
            }
            if (p1Direction==LEFT) {
                p1.x -= (int) plSpeed;
            }
            if (p1Direction==RIGHT) {
                p1.x += (int) plSpeed;
            }
            if (p1Direction==STOP) {
                plSpeed = 0;
            }
        }
    };

    Timer t = new Timer(75,al);
    t.start();
}

//draws the cars and race track
@Override
public void paintComponent(Graphics g) {

    super.paintComponent(g);
    //draw p1
    g.setColor(Color.RED);
    g.fillRect(p1.x,p1.y,p1.width,p1.height);

}

//have to input these (so it will compile)
public void keyPressed(KeyEvent event) {
    System.out.println(event);
    try {
        //makes car increase speed a bit
        if (event.getKeyChar()=='w' ||
            event.getKeyChar()=='a' ||
            event.getKeyChar()=='s' ||
            event.getKeyChar()=='d') {
                plSpeed += .2;
                //repaint();
        }
    } catch (Exception I) {}
}
public void keyReleased(KeyEvent event) {}

//now, to be able to set the direction
public void keyTyped(KeyEvent event) {
    if (plSpeed > 0) {
        if (event.getKeyChar()=='a') {
            if (p1Direction==RIGHT) {
                p1Brake();
            } else {
                if (p1Direction==LEFT) {
                } else {
                    p1Direction = LEFT;
                }
            }
        }
        if (event.getKeyChar()=='s') {
            if (p1Direction==UP) {
                p1Brake();
            } else {
                if (p1Direction==DOWN) {
                } else {
                    p1Direction = DOWN;
                }
            }
        }
        if (event.getKeyChar()=='d') {
            if (p1Direction==LEFT) {
                p1Brake();
            } else {
                if (p1Direction==RIGHT) {
                } else {
                    p1Direction = RIGHT;
                }
            }
        }
        if (event.getKeyChar()=='w') {
            if (p1Direction==DOWN) {
                p1Brake();
            } else {
                if (p1Direction==UP) {
                } else {
                    p1Direction = UP;
                }
            }
        }
        if (event.getKeyChar()=='z') {
            p1Brake();
        }
    }
}

public void p1Brake () {
    try {
        while (plSpeed != 0) {
            plSpeed -= .2;
        }
    } catch (Exception e) {
        plSpeed = 0;
    }
}

//finally, to start the program
public static void main(String[] args) {
    SwingUtilities.invokeLater( new Runnable() {
        public void run() {
            JFrame f = new JFrame("Racing");
            f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
            f.add(new Racing());
            f.pack();
            f.setLocationByPlatform(true);
            f.setResizable( false );
            f.setVisible( true );
        }
    });
}
}