如何检查用户是否按了某个键？

Question

在java中,我有一个程序需要连续检查用户是否按了一个键.所以在伪代码中,有点像

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

提前致谢!

Answer 1

在Java中,你不检查是否有键被按下,而不是你听到KeyEvent秒.实现目标的正确方法是注册KeyEventDispatcher并实现它以维护所需键的状态:

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>")密钥映射及其内部包含的状态IsKeyPressed.

Answer 2

尝试这个：

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());

    }

}