当您拖动蓝色div时，我希望它在释放鼠标按钮时"捕捉"到绿色高亮显示的正方形的中间.我似乎找不到从box[](Path2D())界面读取坐标的方法.那么，有没有一种简单的方法来实现这一点？我应该单独保存正方形的坐标吗？或者我还能以某种方式从Path2D界面中获取点吗？
const board = document.getElementById("board");
const ctxB = board.getContext("2d");
var Grid = false;
const boxsize = 64;
const amountOfrows = 8;
const amountOfHorBoxes = 7;
const totalAmountOfBoxes = amountOfrows * amountOfHorBoxes;
board.width = boxsize * 7.5;
board.height = boxsize * 8;
var addHorBox = 0;
var addVertBox = 0;
let boxes = [];
function drawGrid(){
Grid=true;
// for the amout of rows
for (let rowcount = 0; rowcount < amountOfrows; rowcount++) {
ctxB.lineWidth = 1;
ctxB.strokeStyle = "black";
ctxB.fillStyle = "white";
// filling the rows
if(rowcount%2==0){
for (let boxcount = 0; boxcount < amountOfHorBoxes; boxcount++) {
let box = new Path2D();
box.rect(addHorBox, addVertBox, boxsize, boxsize);
boxes.push(box);
ctxB.fill(box);
ctxB.stroke(box);
addHorBox+=boxsize;
}
}
addHorBox=0;
addVertBox+=boxsize;
}
}
MoveUnit(document.getElementById("unit"));
function MoveUnit(unit){
const rect = board.getBoundingClientRect();
const checkX = unit.clientWidth/2 - rect.left;
const checkY = unit.clientHeight/2 - rect.top;
var initialX;
var initialY;
var tile;
unit.onmousedown = mouseDown;
function mouseDown(e){
e = e || window.event;
e.preventDefault();
initialX = e.clientX;
initialY = e.clientY;
document.onmouseup = mouseUp;
document.onmousemove = moveMouse;
}
function moveMouse(e){
e = e || window.event;
e.preventDefault();
unit.style.top = (unit.offsetTop + e.clientY - initialY) + "px";
unit.style.left = (unit.offsetLeft + e.clientX - initialX) + "px";
boxes.forEach(box => {
if (ctxB.isPointInPath(box, unit.offsetLeft + checkX, unit.offsetTop + checkY)) {
ctxB.lineWidth = 2;
ctxB.fillStyle = 'green';
ctxB.fill(box);
ctxB.stroke(box);
tile=box;
}else{
ctxB.lineWidth = 1;
ctxB.strokeStyle = "black";
ctxB.fillStyle = 'white';
ctxB.fill(box);
ctxB.stroke(box);
}
});
// saving new mousepos after moving the unit
initialX = e.clientX;
initialY = e.clientY;
}
function mouseUp(){
document.onmousemove = false;
}
}
function loop(timestamp){
// draw once
if(Grid==false) drawGrid();
requestAnimationFrame(loop);
}
loop();#board{
background-color: #999;
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
#unit{
background-color: rgb(134, 162, 224);
position: absolute;
cursor: pointer;
z-index: 1;
width: 30px;
height: 30px;
}<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="testing.css"/>
<title>Gridding</title>
</head>
<body>
<div id="unit"></div>
<canvas id="board"></canvas></div>
<script src="testing.js"></script>
</body>
</html>