如何在 Java 中检查按键？

Question

基本上，我正在学习 Java，我正在尝试使用 JavaFX 在 Netbeans 中制作一个简单的游戏。现在，我设置了一个窗口，其中绘制了一个矩形。 （我设置了一个画布来绘制。）我已经创建了一个播放器类和全局类，但我需要知道如何读取关键输入。我是由一位非常擅长 Java 的朋友教我的，所以他给我的信息很好。我阅读了 KeyEvent，但我不知道如何实现它。

非常感谢任何帮助。

Answer 1

几周前我也有同样的问题。问题在于如何随时检查某个键是否被按住。有多种解决方案，我通过使用 bitset 解决了它：

package game.input;

import java.util.BitSet;

import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;

public class Input {

    /**
     * Bitset which registers if any {@link KeyCode} keeps being pressed or if it is released.
     */
    private BitSet keyboardBitSet = new BitSet();

    // -------------------------------------------------
    // default key codes
    // will vary when you let the user customize the key codes or when you add support for a 2nd player
    // -------------------------------------------------

    private KeyCode upKey = KeyCode.UP;
    private KeyCode downKey = KeyCode.DOWN;
    private KeyCode leftKey = KeyCode.LEFT;
    private KeyCode rightKey = KeyCode.RIGHT;
    private KeyCode primaryWeaponKey = KeyCode.SPACE;
    private KeyCode secondaryWeaponKey = KeyCode.CONTROL;

    Scene scene;

    public Input( Scene scene) {
        this.scene = scene;
    }

    public void addListeners() {

        scene.addEventFilter(KeyEvent.KEY_PRESSED, keyPressedEventHandler);
        scene.addEventFilter(KeyEvent.KEY_RELEASED, keyReleasedEventHandler);

    }

    public void removeListeners() {

        scene.removeEventFilter(KeyEvent.KEY_PRESSED, keyPressedEventHandler);
        scene.removeEventFilter(KeyEvent.KEY_RELEASED, keyReleasedEventHandler);

    }

    /**
     * "Key Pressed" handler for all input events: register pressed key in the bitset
     */
    private EventHandler<KeyEvent> keyPressedEventHandler = new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent event) {

            // register key down
            keyboardBitSet.set(event.getCode().ordinal(), true);

        }
    };

    /**
     * "Key Released" handler for all input events: unregister released key in the bitset
     */
    private EventHandler<KeyEvent> keyReleasedEventHandler = new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent event) {

            // register key up
            keyboardBitSet.set(event.getCode().ordinal(), false);

        }
    };


    // -------------------------------------------------
    // Evaluate bitset of pressed keys and return the player input.
    // If direction and its opposite direction are pressed simultaneously, then the direction isn't handled.
    // -------------------------------------------------

    public boolean isMoveUp() {
        return keyboardBitSet.get( upKey.ordinal()) && !keyboardBitSet.get( downKey.ordinal());
    }

    public boolean isMoveDown() {
        return keyboardBitSet.get( downKey.ordinal()) && !keyboardBitSet.get( upKey.ordinal());
    }

    public boolean isMoveLeft() {
        return keyboardBitSet.get( leftKey.ordinal()) && !keyboardBitSet.get( rightKey.ordinal());  
    }

    public boolean isMoveRight() {
        return keyboardBitSet.get( rightKey.ordinal()) && !keyboardBitSet.get( leftKey.ordinal());
    }

    public boolean isFirePrimaryWeapon() {
        return keyboardBitSet.get( primaryWeaponKey.ordinal());
    }

    public boolean isFireSecondaryWeapon() {
        return keyboardBitSet.get( secondaryWeaponKey.ordinal());
    }

}