基于libGDX的Java太空侵略者克隆：玩家飞船无法向右移动

我正在开发一个Java项目，制作《太空侵略者》（Space Invaders）的克隆版。在实现玩家飞船移动功能时，我从StackOverflow找到了一段代码：

if(Gdx.input.isKeyPressed(Input.Keys.LEFT) )
    x -= Gdx.graphics.getDeltaTime() * PlayerSpeed;
if(Gdx.input.isKeyPressed(Input.Keys.RIGHT) )
    x += Gdx.graphics.getDeltaTime() * PlayerSpeed;

我将这段代码应用到了PlayerShip类中：

public class PlayerShip extends Ship {
    private Animator animator;
    private float PlayerSpeed = 20.0f;
    private int x,y;

    public PlayerShip(SpriteBatch batch){
        this.animator=new Animator(batch,"ship.png", 5, 2);
    }

    public void create(){
        animator.create();
    }

    public void render(){
        this.animator.render(this.x,this.y);
        if(Gdx.input.isKeyPressed(Input.Keys.LEFT) )
            x -= Gdx.graphics.getDeltaTime() * PlayerSpeed;
        if(Gdx.input.isKeyPressed(Input.Keys.RIGHT) )
            x += Gdx.graphics.getDeltaTime() * PlayerSpeed;
    }

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

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

主游戏类Game代码如下：

public class Game extends ApplicationAdapter {
    private SpriteBatch batch;

    private BackgroundManagement backgroundManagement;
    private BitmapFont font;

    private PlayerShip player;
    private SmallShip smallShip;


    @Override
    public void create() {
        Gdx.graphics.setWindowedMode(600, 800);
        batch = new SpriteBatch();
        player = new PlayerShip(batch);
        smallShip = new SmallShip(batch);
        player.create();
        player.setX(300);
        player.setY(100);
        smallShip.create();
        smallShip.setX(200);
        smallShip.setY(400);
        font = new BitmapFont(Gdx.files.internal("gamefont.fnt"),
                Gdx.files.internal("gamefont.png"), false);
        backgroundManagement = new BackgroundManagement(batch);
    }

    @Override
    public void render() {
        Gdx.gl.glClearColor(0, 0, 0.2f, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        batch.begin();
        backgroundManagement.render();
        player.render();
        smallShip.render();
        batch.end();
    }

    @Override
    public void dispose() {
        batch.dispose();
    }
}

测试时发现飞船无法向右移动，尝试多种解决方案无效，恳请帮助。

核心问题：整数类型截断导致移动失效 #

你的PlayerShip类中，x和y被定义为int类型，但移动计算时Gdx.graphics.getDeltaTime() * PlayerSpeed是浮点数值：

• 向右移动时，比如PlayerSpeed=20，deltaTime通常在0.016左右，计算结果是0.32，加到int类型的x上时，小数部分会被直接截断，x的整数值不会变化，所以看起来飞船没动。
• 向左移动时，x -= 0.32会让整数x减1（比如300变成299），所以能看到移动效果。

修复步骤 #

1. 修改坐标类型为float
   把PlayerShip中的x、y类型从int改成float，同时更新对应的setter方法：

public class PlayerShip extends Ship {
    private Animator animator;
    private float PlayerSpeed = 20.0f;
    // 改成float类型
    private float x,y;

    public PlayerShip(SpriteBatch batch){
        this.animator=new Animator(batch,"ship.png", 5, 2);
    }

    public void create(){
        animator.create();
    }

    public void render(){
        this.animator.render(this.x,this.y);
        if(Gdx.input.isKeyPressed(Input.Keys.LEFT) )
            x -= Gdx.graphics.getDeltaTime() * PlayerSpeed;
        if(Gdx.input.isKeyPressed(Input.Keys.RIGHT) )
            x += Gdx.graphics.getDeltaTime() * PlayerSpeed;
    }

    // 更新setter为float参数
    public void setX(float x) {
        this.x = x;
    }

    public void setY(float y) {
        this.y = y;
    }
}

2. 调整主类中的坐标设置
   在Game类的create方法中，给player.setX()和player.setY()传入浮点数值（或者直接传int，会自动转float）：

player.setX(300f);
player.setY(100f);

3. 可选：提升移动速度
   当前PlayerSpeed=20移动速度偏慢，可以适当调高数值，比如改成200f，让移动效果更明显：

private float PlayerSpeed = 200.0f;

内容的提问来源于stack exchange，提问作者PedroPereira14