當我按下按鈕時，為什么小球沒有在小球內移動？

Question

我對Java和程序設計非常陌生，因此我嘗試編寫一個簡單的程序，其唯一的工作就是用方向鍵使球移動並用空格鍵跳躍。 程序可以編譯，但是球不動。

我可能不完全了解Applet原理，您能向我解釋我犯的錯誤嗎？

小程序：

package test_game;

import java.applet.Applet;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

public class Starting_Point extends Applet implements Runnable, KeyListener {

    private static final long serialVersionUID = 1L;
    private static final int WIDTH = 700;
    private static final int HEIGHT = 300;
    Character Phil;
    Thread thread;

    @Override
    public void init() {
        setSize(WIDTH,HEIGHT);
        Phil = new Character(50, 200);
    }

    @Override
    public void start() {
        thread = new Thread(this);
        thread.start();
    }

    public void run() {
        while (true) {
            repaint();  
        }
    }

    @Override
    public void paint(Graphics arg0) {
        Phil.paint(arg0);
    }

    @Override
    public void keyPressed(KeyEvent arg0) {
        switch (arg0.getKeyCode()) {
            case (KeyEvent.VK_LEFT): Phil.setX(Phil.getX() - Phil.getDx());
                break;
            case (KeyEvent.VK_RIGHT): Phil.setX(Phil.getX() + Phil.getDx());
                break;
            case (KeyEvent.VK_SPACE): Phil.setDy(Character.gravity * Character.dt);
                Phil.setY(Phil.getY() + .5*Character.gravity*Character.dt*Character.dt + Phil.getDy()*Character.dt + Character.jump);
                break;
        }
    }

    @Override
    public void keyReleased(KeyEvent arg0) {
        // TODO Auto-generated method stub
    }

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

人物類：

package test_game;

import java.awt.Color;
import java.awt.Graphics;

public class Character {

    private int x;
    private int y;
    private int radius = 10;
    Graphics g;
    public static final int gravity = 15;
    private static final double dx = 4;
    public double dy;
    public static final double dt = .2;
    public static final int jump = 30;

    public Character(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public void setX(double d) {
        this.x = (int) d;
    }

    public void setY(double d) {
        this.y = (int) d;
    }

    public double getDx() {
        return dx;
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    public void setDy(double dy) {
        this.dy = dy;
    }

    public double getDy() {
        return dy;
    }

    public void paint(Graphics g) {
        g.setColor(Color.black);
        g.fillOval(x, y, radius, radius);   
    }
}

Answer 1

您已經在代碼內部定義了KeyListener 。 但是，您忘了將此事件偵聽器注冊到組件，因此它從未被調用。

如何注冊您的KeyListener：

將以下代碼放入start() ：

this.addKeyListener(this);

這解決了字符從左右移動的問題，但是跳轉並沒有固定，解決跳轉需要更多代碼來計算所需的正確y +，當前代碼始終加0（使用（int）（您使用的整數）到按空格鍵時的y坐標。