为什么我的Java游戏中的if语句不起作用？

Question

I am creating a modern version of breakout for PC in Java 7, but I have ran into a major problem that I can't seem to fix.

Why won't my if statement execute in this, even if the spacebar is pressed , lives IS greater than 0, and the y coord of the ball is greater than 600?

I already tested this with a lot of print statements and log files, but nothing seems to work.

  import javax.swing.ImageIcon;
  import javax.swing.JFrame;
  import javax.swing.JOptionPane;

  import java.awt.*;
  //import java.awt.event.KeyAdapter;
  import java.awt.event.KeyEvent;
  import java.awt.event.KeyListener;

  public class Game extends JFrame implements Runnable , KeyListener {
private static final long serialVersionUID = 1L;

private Graphics dbg;
private Image dbi;

int level = 0;
int lives = 6;
int powerup = 0;
int blocksGone = 0;
int vy = 0;
int vx = 0;
int by = 640;
int bx = 0;
int[] powerups = new int[8];

ImageIcon i0 = new ImageIcon("paddle.gif");
ImageIcon i1 = new ImageIcon("sidebar.gif");
ImageIcon i2 = new ImageIcon("laserpaddle.gif");
ImageIcon i3 = new ImageIcon("paddleCannon.gif");
ImageIcon i4 = new ImageIcon("laser.gif");
ImageIcon i5 = new ImageIcon("bullet.gif");
ImageIcon i6 = new ImageIcon("lifeIcon.gif");
ImageIcon i7 = new ImageIcon("ball.png");
ImageIcon i8 = new ImageIcon("bomb.png");
ImageIcon i9 = new ImageIcon("atomic.png");
//ImageIcon i10 = new ImageIcon("bullet.gif");

Image paddle;
Image side;
Image bullet;
Image bomb;
Image ball;
Image atomc;
Image life;
Image dead;

int paddlex = 400;
int pdx = 0;


public Game() {
    // TODO Auto-generated constructor stub

    setVisible(true);
    setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
    setTitle("Breakout Smash");
    setSize(1024,560);
    setResizable(false);

    this.addKeyListener(this);

}

@Override
public void run() {
    // TODO Auto-generated method stub

    try {

        init();

        while (true) {

            move();
            Thread.sleep(5);

        }

    } catch (Exception e) {

        System.out.println ("java.lang.Execption in line 25, class Game. Stacktrace:");
        e.printStackTrace();

    }
    }

    // TODO Auto-generated method stub

private void init() {
    // TODO Auto-generated method stub

    paddle = i0.getImage();
    side = i1.getImage();
    ball = i7.getImage();

}

public void paint (Graphics g) {

    dbi = createImage (getWidth(),getHeight());
    dbg = dbi.getGraphics();
    paintComponent(dbg);
    g.drawImage(dbi , 0 , 0 , this);

}

public void paintComponent(Graphics g) {
    // TODO Auto-generated method stub

    super.paint(g);

    g.setColor(Color.DARK_GRAY);
    g.fillRect(0,0,getWidth(),getHeight());
    g.drawImage(side, this.getWidth() - side.getWidth(null), 0, null);
    g.setColor(Color.CYAN);
    g.drawString("Score", 950, 50);
    g.drawString("Lives: " + lives , 880, 50);
    g.drawImage(paddle, paddlex, 520, null);

    g.drawImage(ball, bx, by, null);

    repaint();

}

public void move () {

    //if (by <= getHeight()) {

    if (paddlex > 0 && paddlex < getWidth() - side.getWidth(null) - 50) {

        paddlex += pdx;

    } if (paddlex >= getWidth() - side.getWidth(null) - 50) {

        paddlex-= 2;

    } if (paddlex <= 0) {

        paddlex++;

    }

    if (bx > 0 && bx < getWidth() - side.getWidth(null) && by > 10 && by < getHeight()) {

        bx += vx;
        by -= vy;

    } if (by > 560) {

        by = 575;

        bx = 0;

    } if (bx < 5) {

        bx += 3;
        vx = vx * -1;

    } if (bx > getWidth() - side.getWidth(null) - 5) {

        bx -= 3;
        vx = vx * -1;

    } if (by < 15) {

        by++;
        vy = vy * -1;

    } if (by >= 515 && by <= 515 + paddle.getHeight(null) && bx + 8 > paddlex && bx + 8 < paddlex + paddle.getWidth(null)) {

        vy = vy * -1;
        vy ++;
        vx *= pdx;

        /*if (pdx == -2) {

            vx = vx * -2;

        }

        if (pdx == 2) {

            vx = vx * 2;

        }*/

    }

    //} else {

        //vy = 0;
        //vx = 0;

    //}

}

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

}

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

    int keyCode = e.getKeyCode();

    if (keyCode == KeyEvent.VK_ESCAPE) {

        int quit = JOptionPane.showConfirmDialog(null, "Are you sure you want to quit?", "Quit?", JOptionPane.YES_NO_OPTION);
        if (quit  == 0) System.exit(0);

    }

    else if (keyCode == KeyEvent.VK_LEFT) {

        pdx = -2;

    }

    else if (keyCode == KeyEvent.VK_RIGHT) {

        pdx = 2;

    }       
}

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

    int keyCode = e.getKeyCode();

    if (keyCode == KeyEvent.VK_LEFT) {

        pdx = 0;

    }

    else if (keyCode == KeyEvent.VK_RIGHT) {

        pdx = 0;

    }

    else if (keyCode == KeyEvent.VK_SPACE) {

        //if (by > 600 && lives >= 0) { // this is my problem here

            lives--;

            vy = 1;
            vx = pdx;

            bx = paddlex + 10;
            by = 500;

            System.out.println ("Space hit!");

            /*if (lives == 0) {

                JOptionPane.showMessageDialog(null, "Game Over!" , "!", JOptionPane.WARNING_MESSAGE);

            }

        }   */      

    }

}

 }

There must be something I'm not seeing in my code. The big question is: Why won't the ball respawn on the spacebar press and subtract one life at the same time?

Answer 1

Put

System.out.println("by:"+by+"   lives:"+lives);

before the if.

cases:

if(you dont see anything in the console){
     something is wrong with the way you get the input
}
else if(the value of `by` OR `lives` are not correct){
     search somewhere else in your code where you are changing the by and lives
}