对象中的 Javascript 键盘事件

Question

我的键盘以一种简单的方式工作:

rightPressed = false;

onKeyDown = function(pressEvent) {
  if (pressEvent.keyCode == 39) rightPressed = true;
}
onKeyUp = function(pressEvent) {
  if (pressEvent.keyCode == 39) rightPressed = false;
}

$(document).keydown(onKeyDown);
$(document).keyup(onKeyUp);

它奏效了。然后我试图把它全部放在一个类中:

function Tkeyboard(){
this.rightPressed = false;

this.onKeyDown = function(pressEvent) {
  if (pressEvent.keyCode == 39) { this.rightPressed = true; alert("boom!"); }
}
this.onKeyUp = function(pressEvent) {
  if (pressEvent.keyCode == 39) { this.rightPressed = false; }
}

$(document).keydown(this.onKeyDown);
$(document).keyup(this.onKeyUp);
}

在初始化中，我创建了一个对象:

keys = new Tkeyboard;

在主循环中，我采取了行动:

if ( keys.rightPressed ) { rx+=1;}

而现在它失败了。问题的有趣部分是 alert("boom!") 被调用，所以变量也应该被修改......

我会很感激任何想法。

Answer 1

keydown/up 回调在实际运行时会失去其原始范围。您需要 bind回调到 this .在 Prototype Framework ，你会这样做:

function Tkeyboard() {
    this.rightPressed = false;

    $(document).keydown(this.onKeyDown.bind(this));
    $(document).keyup(this.onKeyUp.bind(this));
}

Tkeyboard.prototype.onKeyDown = function(pressEvent) {
  if (pressEvent.keyCode == 39) { this.rightPressed = true; alert("boom!"); }
};
Tkeyboard.prototype.onKeyUp = function(pressEvent) {
  if (pressEvent.keyCode == 39) { this.rightPressed = false; }
};

jQuery 中应该类似.

如果您需要了解如何构建完整的键盘类，请查看 the one I wrote .