addEventListener keydown不工作 [英] addEventListener keydown not working

问题描述

我在互联网上提供了一些基本的Pong代码并试图添加按键，代码在这里： http://cssdeck.com/labs/ping-pong-game-tutorial-with-html5-canvas-and-sounds

I took some basic Pong code available on the internet and tried to add keypresses, the code is here: http://cssdeck.com/labs/ping-pong-game-tutorial-with-html5-canvas-and-sounds

我添加了这个：

canvas.addEventListener("keydown", handlekeydown, true);

在此现有代码之后：

canvas.addEventListener("mousemove", trackPosition, true);
canvas.addEventListener("mousedown", btnClick, true);

我还添加了这个：

function handlekeydown(e) {
  console.log("debug");
  console.log("keycode: "+e.keyCode);
}

但即使我尝试按各种键，也不会调用该函数。为什么是这样？我很确定画布是焦点。

But the function is never called even though I try pressing various keys. Why is this? I'm pretty sure the Canvas is in focus.

推荐答案

你不能指定 keydown 事件到画布，因为您无法使用光标聚焦画布。您需要将事件分配给窗口：

You can't assign the keydown event to the canvas because you can't focus the canvas with the cursor. You will need to assign the event to the window:

window.addEventListener("keydown", handle, true);

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