我有一个 class 对象TextManager
,它有一些xx
在构造函数中最初设置为零的数字。我希望能够xx
在文本区域更改时更新对象的变量。
class Drawer {
canvasElement: HTMLCanvasElement;
constructor(_canvasElement: HTMLCanvasElement) {
this.canvasElement = _canvasElement;
}
drawCircle(x:number,y:number,radius:number,color:string) {
var ctx = this.canvasElement.getContext("2d");
ctx.beginPath();
ctx.arc(x, y, radius, 0, 2 * Math.PI);
ctx.fillStyle = color;
ctx.closePath();
ctx.fill();
}
}
var canv;
var drawer;
var d = 0;
var textAreaElement;
var textManager;
class TextManager{
textAreaElement: HTMLAreaElement;
xx: number;
constructor(_textAreaElement: HTMLAreaElement) {
this.textAreaElement = _textAreaElement;
this.xx = 0;
this.textAreaElement.onchange = this.update;
}
update() {
this.xx += 10;
if (this.xx > 50) this.xx = 0;
drawer.drawCircle(95 + this.xx, 50, 40, "#FF0000");
}
}
window.onload = () => {
canv = <HTMLCanvasElement>document.getElementById("myCanvas");
drawer = new Drawer(canv);
textAreaElement = <HTMLAreaElement>document.getElementById("codeArea");
textManager = new TextManager(textAreaElement);
};
问题是在代码中使用这种方式会导致xx = NaN
. 因为我认为它没有访问成员,它只是访问类中的函数。
如何在xx
每次事件发生时更新对象?