AWT KeyListener 反应慢

Question

我正在使用 Java Swing 创建一个简单的游戏。我有一个问题 - KeyListener 的反应似乎有点不稳定/缓慢。角色使用以下代码移动：

// player control
    public void keyPressed(KeyEvent e) {
        int key = e.getKeyCode();
        switch(key){
        case(KeyEvent.VK_LEFT): dx = -speed; break;
        case(KeyEvent.VK_RIGHT): dx = speed; break;
        case(KeyEvent.VK_UP): dy = -speed; break;
        case(KeyEvent.VK_DOWN): dy = speed; break;
        }
    }

public void keyReleased(KeyEvent e) {
    int key = e.getKeyCode();
    switch(key){
    case(KeyEvent.VK_LEFT): dx = 0; break;
    case(KeyEvent.VK_RIGHT): dx = 0; break;
    case(KeyEvent.VK_UP): dy = 0; break;
    case(KeyEvent.VK_DOWN): dy = 0; break;
    }
}

// this method is performed each time before redrawing the screen
public void step() {
    x += dx;
    y += dy;
}

大多数时候一切都很好，但有时角色会在对键盘做出反应之前停止一段时间。如何让键盘输入更流畅？

Answer 1

感谢大家的回答！他们帮助我走上正轨。

正如我在评论中所说，这里发生的情况如下： 例如，如果我们按住右键 - 角色向右移动，那么我们按下左键，它开始向左移动。现在，如果我们松开右键，xSpeed 将重置为零，KeyListener 必须等到再次触发keyPressed()，因为我们仍然按住左键。 “按键重复速度”是默认设置的，据我了解无法调整。

所以解决方案是跟踪当前按下了哪些键，这样当我们仍然按住左键时，我们不必在释放右键时将角色的速度降为零。

抱歉，举了一个有点神秘的例子，只是尽量保持代码小：

// Define keys: up, right, down, left
// 0 - not pressed, 1 - pressed
private int[] keys = {0, 0, 0, 0};

// player control
public void keyPressed(KeyEvent e) {
    int key = e.getKeyCode();
    // we set the corresponding 'key indicator' to 1 when it is pressed
    switch(key){
        case(KeyEvent.VK_LEFT): dx = -speed; keys[3] = 1; break; 
        case(KeyEvent.VK_RIGHT): dx = speed; keys[1] = 1; break;
        case(KeyEvent.VK_UP): dy = -speed; keys[0] = 1; break;
        case(KeyEvent.VK_DOWN): dy = speed; keys[2] = 1; break;
        case(KeyEvent.VK_SPACE): fireOn = true; break;
    }
}

public void keyReleased(KeyEvent e) {
    int key = e.getKeyCode();
    // now before resetting the speed we check if the opposite key
    // is still pressed
    switch(key){
        case(KeyEvent.VK_LEFT): if(keys[1]==0){dx = 0;} keys[3] = 0; break;
        case(KeyEvent.VK_RIGHT): if(keys[3]==0){dx = 0;} keys[1] = 0; break;
        case(KeyEvent.VK_UP): if(keys[2]==0){dy = 0;} keys[0] = 0; break;
        case(KeyEvent.VK_DOWN): if(keys[0]==0){dy = 0;} keys[2] = 0; break;
        case(KeyEvent.VK_SPACE): fireOn = false; break;
    }
}

Answer 2

另一种方法可能会有所帮助：

object.addKeyListener(new KeyAdapter() {
    @Override
    public void keyTyped(KeyEvent e) {
        updateOpreation();
    }

    @Override
    public void keyReleased(KeyEvent e) {
        updateOpreation();
    }

    @Override
    public void keyPressed(KeyEvent e) {
        updateOpreation();
    }

}