Jetpack Joyride 用户移动

Question

我正在尝试创建一个类似于喷气背包兜风的游戏，在该游戏中，用户可以按住空格键向上并松开向下旅行。我正在使用计时器来模拟重力并使用keyPressed 和keyReleased 来检查用户是否按住空格键。我正在使用打印语句来确定 keyPressed 和 keyReleased 都在工作，但我不知道为什么物理没有运行。我不知道问题是否是我的 if 语句没有更新，是否是在 if 语句中创建的新计时器。无论哪种方式，重力都没有改变，我被卡住了。感谢您的帮助。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Timer;
import java.util.TimerTask;
import java.util.Calendar;



public class Game implements KeyListener {
    JFrame frame;
    JLabel player;

    public boolean grounded = false;
    public int velocity = 0;
    public int finalY = 0;
    public boolean spaceHeld = false;


    Action spaceAction;

    Game() {
         
        frame = new JFrame("Nicholas Seow-Xi Crouse");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(1920, 1080);
        frame.setLayout(null);
        
        frame.setFocusable(true);
        frame.addKeyListener(this);

        player = new JLabel();
        player.setBackground(Color.red);
        player.setBounds(10, 1800, 50, 50);
        player.setOpaque(true);

        frame.add(player);
        frame.setVisible(true);
        
         Timer flightTime = new Timer();
         TimerTask flight = new TimerTask() {
         
            public void run() {
                  if(velocity > -5) {
                  velocity -= 1;
                  }
                  else{
                  velocity = -5;
                  }
                  if (finalY < -61) {
                   finalY = finalY + velocity;
                   }
                   else{
                   finalY = -61;
                   }
                   player.setLocation(player.getX(), player.getY() + finalY);
                   if (player.getY() <= 0){
                   cancel();
                   velocity = 0;
                   finalY = 0;
                   player.setLocation(player.getX(), 0);
                    
                   }  
            }
      };
         

         Timer gravityTime = new Timer();
         TimerTask gravity = new TimerTask() {


            //creates a timer run method that simulates the falling gravity when not grounded
            public void run() {
                if(velocity < 5){
                velocity += 1;
                }
                else{
                velocity = 5;
                }
                //creates the variable the tells where the player is located
                if (finalY < 61) {
                finalY = finalY + velocity;
                }
                else{
                finalY = 61;
                }
                player.setLocation(player.getX(), player.getY() + finalY);
                if (player.getY() >= 1000){
                cancel();
                velocity = 0;
                finalY = 0;
                player.setLocation(player.getX(), 990); 
                }
                
            }
        };

        if (spaceHeld == false ) {
            gravityTime.scheduleAtFixedRate(gravity, 0, 33);
        }
        if (spaceHeld == true ) {
            flightTime.scheduleAtFixedRate(flight, 0 ,33);
    }
}

public void keyTyped(KeyEvent e) {
}

public void keyPressed(KeyEvent e) {
if(e.getKeyCode() == KeyEvent.VK_SPACE){
spaceHeld = true;
//debug
System.out.println(spaceHeld);
}
}

public void keyReleased(KeyEvent e) {
if(e.getKeyCode() == KeyEvent.VK_SPACE){
spaceHeld = false;
//debug
System.out.println(spaceHeld);
}
}
}

Answer 1

代码是基于事件的，目前没有任何东西会触发您的计时器启动。为此，您只需在关键事件中移动计时器计划/开始操作：

public void keyPressed(KeyEvent e) {
    if(e.getKeyCode() == KeyEvent.VK_SPACE){

            //Cancel the other timer here so that they don't overlap
            gravity.cancel();
            gravityTime.cancel();

            //Create a new instance of the timer
            flightTime = new Timer();
            flight = new TimerTask() {
     
                public void run() {
                    if(velocity > -5) {
                        velocity -= 1;
                    }
                    else{
                        velocity = -5;
                    }
                    if (finalY < -61) {
                        finalY = finalY + velocity;
                    }
                    else{
                        finalY = -61;
                    }

                    player.setLocation(player.getX(), player.getY() + finalY);
                    if (player.getY() <= 0){
                        cancel();
                        velocity = 0;
                        finalY = 0;
                        player.setLocation(player.getX(), 0);
                    }  
                }
            };

            //Now start the timer
            flightTime.scheduleAtFixedRate(flight, 0 ,33);
        }
    }
    
    //Do the same for the gravity method
    public void keyReleased(KeyEvent e) {
        if(e.getKeyCode() == KeyEvent.VK_SPACE){

            ......

        }
    }
}

请注意，您还应该取消具有相反键事件的其他计划任务，以免它们相互重叠并重视奇怪的结果。

要使 keyPressed 方法可以访问 flightTime 和 gravityTime，只需将它们声明为类变量：

public class Game implements KeyListener {
    JFrame frame;
    JLabel player;

    public boolean grounded = false;
    public int velocity = 0;
    public int finalY = 0;
    public boolean spaceHeld = false;

    //Move them here but don't assign a value:
    public Timer flightTime;
    public TimerTask flight;
    public Timer gravityTime;
    public TimerTask gravity;

您仍然可以稍后在 Game 方法中创建对象：

flightTime = new Timer();
flight = new TimerTask() {
    ....
};