如何检查用户是否按了某个键？

问题描述

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psuedocode中，类似于

In java I have a program that needs to check continuously if a user is pressing a key.So In psuedocode, somthing like

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

提前致谢！

推荐答案

在java中你不会检查是否按下了某个键，而是 listen 到 KeyEvent 秒。
实现目标的正确方法是注册 KeyEventDispatcher ，并实现它以维持所需密钥的状态：

In java you don't check if a key is pressed, instead you listen to KeyEvents.The right way to achieve your goal is to register a KeyEventDispatcher, and implement it to maintain the state of the desired key:

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;
                }
            }
        });
    }
}

然后你可以随时使用：

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

当然，您可以使用相同的方法来实现 isPressing（< some key>）带有键的映射及其状态包含在 IsKeyPressed 中。

You can, of course, use same method to implement isPressing("<some key>") with a map of keys and their state wrapped inside IsKeyPressed.

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