您好，我正在尝试编写一个简单的程序来娱乐..但是我无法获得旋转角度并将其转换为针跟随十字线后降落的数字。我让针跟随表盘内。我包括我的 javascript 代码。有人可以帮我吗？
function alienEye(x, y, size, append, img, theNum) {
var self = this;
var i = 0;
var myintID;
this.x = x;
this.y = y;
this.size = size;
//Create the Eye Dom Node using canvas.
this.create = function create(x, y, size, append) {
//Create dom node
var eye = document.createElement('canvas');
eye.width = size;
eye.height = size;
eye.style.position = 'relative';
eye.style.top = y + 'px';
eye.style.left = x + 'px';
document.getElementById(append).appendChild(eye);
//Get canvas
canvas = eye.getContext("2d")
radius = size / 2;
//draw eye
//canvas.beginPath();
//canvas.arc(radius, radius, radius, 0, Math.PI*2, true);
//canvas.closePath();
//canvas.fillStyle = "rgb(255,255,255)";
//canvas.fill();
//draw pupil
//canvas.beginPath();
//canvas.arc(radius, radius/2, radius/4, 0, Math.PI*2, true);
//canvas.closePath();
//canvas.fillStyle = "rgb(0,0,0)";
//canvas.fill();
//var img = new Image();
canvas.drawImage(img, - 20, - 20, 100, 100);
img.onload = function () {
canvas.drawImage(img, - 20, - 20, 100, 100);
}
img.src = 'Stuff/needle.png';
return eye;
}
//Rotate the Dom node to a given angle.
this.rotate = function (x) {
this.node.style.MozTransform = "rotate(" + x + "deg)";
this.node.style.WebkitTransform = "rotate(" + x + "deg)";
this.node.style.OTransform = "rotate(" + x + "deg)";
this.node.style.msTransform = "rotate(" + x + "deg)";
this.node.style.Transform = "rotate(" + x + "deg)";
}
this.letsBegin = function () {
//Update every 100 miliseconds
myintID = setInterval(function () {
//Math!
angleFromEye = Math.atan2((cursorLocation.y - self.my_y), cursorLocation.x - self.my_x) * (180 / Math.PI) + 90;
//Rotate
self.rotate(angleFromEye);
//Refresh own position every 25th time (in case screen is resized)
i++;
if (i > 25) {
self.locateSelf();
i = 0;
}
}, 20);
}
this.letsEnd = function () {
clearInterval(myintID);
}
this.locateSelf = function () {
this.my_x = this.node.offsetLeft + (this.size / 2);
this.my_y = this.node.offsetTop + (this.size / 2);
//If it has offsetParent, add em up to get the objects full position.
if (this.node.offsetParent) {
temp = this.node;
while (temp = temp.offsetParent) {
this.my_x += temp.offsetLeft;
this.my_y += temp.offsetTop;
}
}
}
//Call the node create function when the AlienEye Object is created.
this.node = this.create(x, y, size, append);
this.locateSelf();
//Now the node has been added to the page, lets figure out exact where
//it is relative to the documents top.
//Get the basic position
var cursorLocation = new function () {
this.x = 0;
this.y = 0;
//This function is called onmousemove to update the stored position
this.update = function (e) {
var w = window,
b = document.body;
this.x = e.clientX + (w.scrollX || b.scrollLeft || b.parentNode.scrollLeft || 0);
this.y = e.clientY + (w.scrollY || b.scrollTop || b.parentNode.scrollTop || 0);
}
//Hook onmousemove up to the above update function.
document.onmousemove = function (e) {
cursorLocation.update(e);
};