Java KeyEvent注册未按下的键

Question

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

public class IsKeyPressed {
    private static volatile boolean qPressed = false;
    private static volatile boolean wPressed = false;

    public static boolean isQPressed() {
        synchronized (IsKeyPressed.class) {
            return qPressed;
        }
    }

    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;
                        } else if (ke.getKeyCode() == KeyEvent.VK_Q) {
                            qPressed = true;
                        }
                        break;

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

    public void keyTyped(KeyEvent ke) {
        //test
    }

    public void keyPressed(KeyEvent ke) {
        //test
    }

    public void keyReleased(KeyEvent ke) {
        //test
    }
}

Java中的公共类

static boolean randomVariableName = true;

    public static void main(String[] args) {
        while (randomVariableName == true) {
            if (IsKeyPressed.isWPressed()); {
                System.out.println("keydown.W");
            }
            if (IsKeyPressed.isQPressed()); {
                System.out.println("keydown.Q");
            }
        }
    }

我希望在键盘上按Q会使控制台打印keydown.Q，但它只是垃圾邮件keydown.Q和keydown.w

Answer 1

以下将使您的代码成为垃圾邮件：

 if (IsKeyPressed.isWPressed()); {
     System.out.println("keydown.W");
 }

isWPressed（）后面的分号终止表达式，所以总是true...

无垃圾邮件：

 if (IsKeyPressed.isWPressed()) {
     System.out.println("keydown.W");
 }