我试图开发一个JavaScript游戏引擎,我遇到了这个问题:

当我按空格键时,角色会跳跃。 当我按下→角色向右移动。

问题是,当我按右键,然后按空格键时,角色会跳跃,然后停止移动。

我使用keydown函数来按下键。如何检查是否同时按下了多个键?


当前回答

对于任何使用React的人,这里是我的解决方案:

import { useEffect, useState } from "react";
import Backdrop from '@mui/material/Backdrop';

export const Example = () => {
  const [backdropOpen, setBackdropOpen] = useState(false);

  useEffect(() => {
    // Keys that need to be pressed at the same time in order for
    // the 'backdropOpen' variable to be 'true'
    const keysArr = ['ControlLeft', 'ShiftLeft', 'AltLeft'];
    const keysMap = {};
    let backdropOpenLocal = false;

    const keydownEvent = 'keydown';
    const keyupEvent = 'keyup';

    const checkKeys = () => {
      const keysArePressed = keysArr.every((value) => keysMap[value] === keydownEvent);
      if (keysArePressed !== backdropOpenLocal) {
        backdropOpenLocal = keysArePressed;
        setBackdropOpen(keysArePressed);
      }
    }

    const handleKeyDown = (event) => {
      const keyCode = event.code;
      if (keysArr.includes(keyCode) && keysMap[keyCode] !== keydownEvent) {
        keysMap[keyCode] = keydownEvent;
      }
      checkKeys();
    }

    const handleKeyUp = (event) => {
      const keyCode = event.code;
      if (keysArr.includes(keyCode) && keysMap[keyCode] !== keyupEvent) {
        keysMap[keyCode] = keyupEvent;
      }
      checkKeys();
    }

    document.addEventListener('keydown', handleKeyDown);
    document.addEventListener('keyup', handleKeyUp);

    return () => {
      document.removeEventListener('keydown', handleKeyDown);
      document.removeEventListener('keyup', handleKeyUp);
    }
  }, []);

  return (
    <React.Fragmemnt>
      <div>
        <Backdrop
          open={backdropOpen}
        >
          <span>
            It worked!
          </span>
        </Backdrop>
      </div>
    </React.Fragmemnt>
  );
}

请记住,我们需要在useEffect函数中使用backdropOpenLocal而不是backdropOpen,因为我们只想更新局部作用域变量并保持作用域的状态。

如果我们更新Example组件的状态并尝试访问backdropOpen,我们将得到与之前相同的值,除非我们在useEffect的依赖数组中传递backdropOpen;这将导致useEffect内的作用域变量被重置,我们不希望这样。

其他回答

    $(document).ready(function () {
        // using ascii 17 for ctrl, 18 for alt and 83 for "S"
        // ctr+alt+S
        var map = { 17: false, 18: false, 83: false };
        $(document).keyup(function (e) {
            if (e.keyCode in map) {
                map[e.keyCode] = true;
                if (map[17] && map[18] && map[83]) {
                    // Write your own code here, what  you want to do
                    map[17] = false;
                    map[18] = false;
                    map[83] = false;
                }
            }
            else {
                // if u press any other key apart from that "map" will reset.
                map[17] = false;
                map[18] = false;
                map[83] = false;
            }
        });

    });

这是布雷登斯答案的一个实现。

Var键= {} handleKeyPress(evt) { let {keyCode, type} = evt ||事件;//处理IE let isKeyDown = (type == 'keydown'); keys[keyCode] = isKeyDown; // test: enter键被按下,shift键没有被按下 if(isKeyDown && keys[13] && !keys[16]){ Console.log('用户按下enter没有shift') } }; 窗口。addEventListener(“弹起”,handleKeyPress); 窗口。addEventListener(“keydown”,handleKeyPress);

谁需要完整的示例代码。左+右补充道

var keyPressed = {};
document.addEventListener('keydown', function(e) {

   keyPressed[e.key + e.location] = true;

    if(keyPressed.Shift1 == true && keyPressed.Control1 == true){
        // Left shift+CONTROL pressed!
        keyPressed = {}; // reset key map
    }
    if(keyPressed.Shift2 == true && keyPressed.Control2 == true){
        // Right shift+CONTROL pressed!
        keyPressed = {};
    }

}, false);

document.addEventListener('keyup', function(e) {
   keyPressed[e.key + e.location] = false;

   keyPressed = {};
}, false);

我喜欢使用这个片段,它对于编写游戏输入脚本非常有用

var keyMap = [];

window.addEventListener('keydown', (e)=>{
    if(!keyMap.includes(e.keyCode)){
        keyMap.push(e.keyCode);
    }
})

window.addEventListener('keyup', (e)=>{
    if(keyMap.includes(e.keyCode)){
        keyMap.splice(keyMap.indexOf(e.keyCode), 1);
    }
})

function key(x){
    return (keyMap.includes(x));
}

function checkGameKeys(){
    if(key(32)){
        // Space Key
    }
    if(key(37)){
        // Left Arrow Key
    }
    if(key(39)){
        // Right Arrow Key
    }
    if(key(38)){
        // Up Arrow Key
    }
    if(key(40)){
        // Down Arrow Key
    }
    if(key(65)){
        // A Key
    }
    if(key(68)){
        // D Key
    }
    if(key(87)){
        // W Key
    }
    if(key(83)){
        // S Key
    }
}

我使用case, if和bool。我有一个项目,这对我很有效


window.addEventListener("keydown", onKeyDown, false);
window.addEventListener("keyup", onKeyUp, false);

function onKeyDown(event) {
  var keyCode = event.keyCode;
  switch (keyCode) {
    case 68: //D
      keyd = true;
      break;
    case 32: //spaaaaaaaaaaaaaaace
      keyspace = true;
      break;
    case 65: //A
      keya = true;
      break;
    case 37:
      keya = true;
      break;
    case 38:
      keyspace = true;
      break;
    case 39:
      keyd = true;
      break;
  }
}

function onKeyUp(event) {
  var keyCode = event.keyCode;

  switch (keyCode) {
    case 68: //dddddd
      keyd = false;
      break;
    case 32: //spaaaaaaaaaaaaaaaaaaaaaace
      keyspace = false;
      break;
    case 65: //aaaaa
      keya = false;
      break;
    case 37:
      keya = false;
      break;
    case 38:
      keyspace = false;
      break;
    case 39:
      keyd = false;
      break;
  }
}