重新绘制会传送我的图形，而不是平滑地移动它

Question

因此，在我的代码中，当我按下W、A、S或D键之一时，我会按所需方向重新绘制图形。图形不是从左到右或上下平滑移动，而是变得不可见，有时还会再次可见，但如果我松开正在按下的键，它总是会变得可见。我在另一台电脑上创建了完全相同的程序，这个问题没有出现，但在我的个人电脑上，它总是存在。

    import com.sun.glass.events.KeyEvent;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Shape;
/**
 *
 * @author Admin
 */
public class mainFrame extends javax.swing.JFrame {
    public static int px,py,pwid,phei,ex,ey,ewid,ehei,speed,ppx,ppy;
    /**
     * Creates new form mainFrame
     */
    public mainFrame() {
        initComponents();
        px = 150;py = 150;pwid = 50;phei = 50;speed = 10000;
    }
    public void paint(Graphics g){
        super.paint(g);
        Graphics player = (Graphics)g;
        player.drawRect(px, py, pwid, phei);
    }
    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        addKeyListener(new java.awt.event.KeyAdapter() {
            public void keyPressed(java.awt.event.KeyEvent evt) {
                formKeyPressed(evt);
            }
        });
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 300, Short.MAX_VALUE)
        );
        pack();
    }// </editor-fold>                        
    private void formKeyPressed(java.awt.event.KeyEvent evt) {                                
        int keycode = evt.getKeyCode();
        if(keycode == KeyEvent.VK_D){    
            repaint(px++*speed);
        }if(keycode == KeyEvent.VK_A){    
            repaint(px--*speed);
        }if(keycode == KeyEvent.VK_W){    
            repaint(py--*speed);
        }if(keycode == KeyEvent.VK_S){    
            repaint(py++*speed);
        }
        if(px >= 400-42 || px <= 0+42){
            px = px - 1;
        }else if(py >= 300-42 || py <= 0+42){
            System.out.println("You Cant go there");
        }
    }                               
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(mainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(mainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(mainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(mainFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new mainFrame().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    // End of variables declaration                   
}

Answer 1

这并不是repaint(int)背后的想法，相反，您应该有一个"游戏循环"，它更新游戏的当前状态并安排重新绘制。

此外，您确实应该避免覆盖顶级容器的paint，因为正如您所发现的，它们不是双缓冲的，这可能会在更新时导致闪烁。JFrame还包含一组其他组件，由于绘画的工作方式，这些组件可以独立于容器进行绘画，这意味着它们可以找到你以前画过的

相反，从JPanel开始，覆盖其paintComponent方法，并在其中执行自定义绘制，然后将此面板添加到JFrame 的实例中

您还应该避免使用KeyListener，原因有很多（焦点相关的问题是主要问题），而更喜欢密钥绑定API

Answer 2

获取您的"player"对象，并为其创建一个名为player 的显式类

示例：

class Player extends JComponent {
    //unique player fields here
    /**
     * Method to draw this particular component.
     */
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        // insert content of your paint method here
    }
}

当您想将播放器组件添加到JFrame时，请使用：

this.getContentPane().add(new Player());

MadProgrammer介绍了我想说的关于键盘输入和缺少游戏循环的事情。