java - 如何检查用户是否在按键？

Question

在 java 中，我有一个程序需要连续检查用户是否按下键。所以在伪代码中，类似

if (isPressing("w"))
{
 //do somthing
}

提前致谢！

Answer 1

在java中，您不检查是否按下了键，而是听sKeyEvent . 实现目标的正确方法是注册 aKeyEventDispatcher并实现它以维护所需密钥的状态：

import java.awt.KeyEventDispatcher;
import java.awt.KeyboardFocusManager;
import java.awt.event.KeyEvent;

public class IsKeyPressed {
    private static volatile boolean wPressed = false;
    public static boolean isWPressed() {
        synchronized (IsKeyPressed.class) {
            return wPressed;
        }
    }

    public static void main(String[] args) {
        KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(new KeyEventDispatcher() {

            @Override
            public boolean dispatchKeyEvent(KeyEvent ke) {
                synchronized (IsKeyPressed.class) {
                    switch (ke.getID()) {
                    case KeyEvent.KEY_PRESSED:
                        if (ke.getKeyCode() == KeyEvent.VK_W) {
                            wPressed = true;
                        }
                        break;

                    case KeyEvent.KEY_RELEASED:
                        if (ke.getKeyCode() == KeyEvent.VK_W) {
                            wPressed = false;
                        }
                        break;
                    }
                    return false;
                }
            }
        });
    }
}

然后你总是可以使用：

if (IsKeyPressed.isWPressed()) {
    // do your thing.
}

当然，您可以使用相同的方法来实现isPressing("<some key>")键映射及其包裹在IsKeyPressed.

Answer 2

试试这个：

import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.JFrame;
import javax.swing.JTextField;

public class Main {

    public static void main(String[] argv) throws Exception {

    JTextField textField = new JTextField();

    textField.addKeyListener(new Keychecker());

    JFrame jframe = new JFrame();

    jframe.add(textField);

    jframe.setSize(400, 350);

    jframe.setVisible(true);

}

class Keychecker extends KeyAdapter {

    @Override
    public void keyPressed(KeyEvent event) {

        char ch = event.getKeyChar();

        System.out.println(event.getKeyChar());

    }

}

Answer 3

通用方法

我基于@Elist 的方法构建了一个便利实用程序类，它适用于任何键。

import java.awt.*;
import java.awt.event.KeyEvent;
import java.util.HashMap;
import java.util.Map;

public class Keyboard {

    private static final Map<Integer, Boolean> pressedKeys = new HashMap<>();

    static {
        KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(event -> {
            synchronized (Keyboard.class) {
                if (event.getID() == KeyEvent.KEY_PRESSED) pressedKeys.put(event.getKeyCode(), true);
                else if (event.getID() == KeyEvent.KEY_RELEASED) pressedKeys.put(event.getKeyCode(), false);
                return false;
            }
        });
    }

    public static boolean isKeyPressed(int keyCode) { // Any key code from the KeyEvent class
        return pressedKeys.getOrDefault(keyCode, false);
    }
}

示例用法：

do {
    if (Keyboard.isKeyPressed(KeyEvent.VK_W)) System.out.println("W is pressed!");
} while (!Keyboard.isKeyPressed(KeyEvent.VK_ESCAPE));

Answer 4

你必须实现KeyListener，看看这里： http ://docs.oracle.com/javase/7/docs/api/java/awt/event/KeyListener.html

有关如何使用它的更多详细信息：http: //docs.oracle.com/javase/tutorial/uiswing/events/keylistener.html