我使用触摸和鼠标事件在HTML / CSS / JS中创建了拖放操作。如果用户将对象拖动到盒子外面，则该对象应返回到拖动开始之前的原始位置。但是，我不知道该怎么做。
当前，我正在使用setTranslate(0, 0, dragItem);使对象移到红色框的左上角。我尝试使用setTranslate(initialX, initialY, dragItem);将其恢复到原始位置，但这似乎不起作用，因为我相信变量initialX和initialY会跟踪鼠标或手指而不是对象的原始位置。当我使用setTranslate(initialX, initialY, dragItem);时，对象从鼠标“逃跑”。
下面和this link处的完整代码。
<!DOCTYPE html>
<html>
<head>
<!--<meta name="viewport"
content="width=device-width,
initial-scale=1.0,
user-scalable=no" />
<title>Drag/Drop/Bounce</title>-->
<style>
#item {
width: 100px;
height: 100px;
background-color: rgb(245, 230, 99);
border: 10px solid rgba(136, 136, 136, .5);
border-radius: 50%;
touch-action: none;
user-select: none;
position: absolute;
}
#box1 {
width: 200px;
height: 200px;
background-color: red;
}
#box2 {
width: 200px;
height: 200px;
background-color: lightblue;
}
</style>
</head>
<body>
<h1>Drag and Drop</h1>
<div id="item"></div>
<div id="box1">
</div>
<br>
<div id="box2"></div>
<script>
var dragItem = document.querySelector("#item");
var box1 = document.querySelector("#box1");
var box2 = document.querySelector("#box2");
var container = dragItem;
//Declare Variables
var active = false;
var currentX;
var currentY;
var initialX;
var initialY;
var xOffset = 0;
var yOffset = 0;
//Add Event Listeners for Touchscreens
container.addEventListener("touchstart", dragStart, false);
container.addEventListener("touchend", dragEnd, false);
container.addEventListener("touchmove", drag, false);
//Add Event Listeners for Mice
container.addEventListener("mousedown", dragStart, false);
container.addEventListener("mouseup", dragEnd, false);
container.addEventListener("mousemove", drag, false);
function dragStart(e) { //when the drag starts
if (e.type === "touchstart") { //if its a touchscreen
initialX = e.touches[0].clientX - xOffset; //set initial x-cordinate to where it was before drag started
initialY = e.touches[0].clientY - yOffset; //set initial y-cordinate to where it was before drag started
} else { //if its not a touchscreen (mouse)
initialX = e.clientX - xOffset; //set initial x-cordinate to where it was before drag started
initialY = e.clientY - yOffset; //set initial y-cordinate to where it was before drag started
}
if (e.target === dragItem) { //if user is dragging circle
active = true; //the drag is active
}
}
function dragEnd(e) { //when the drag ends
const box1Size = box1.getBoundingClientRect(); //the size of box1
const box2Size = box2.getBoundingClientRect(); //the size of box2
const elementSize = dragItem.getBoundingClientRect(); //the size of the circle
if (elementSize.left >= box1Size.left && elementSize.right <= box1Size.right && elementSize.top >= box1Size.top && elementSize.bottom <= box1Size.bottom) { //if the circle is in box1
initialX = currentX; //set the initial x-cordinate to where it is now
initialY = currentY; //set the initial y-cordinate to where it is now
} else if (elementSize.left >= box2Size.left && elementSize.right <= box2Size.right && elementSize.top >= box2Size.top && elementSize.bottom <= box2Size.bottom) { //if the circle is in box2
initialX = currentX; //set the initial x-cordinate to where it is now
initialY = currentY; //set the initial y-cordinate to where it is now
}
else { //if the circle is in neither box1 nor box2
currentX = 0;
currentY = 0;
initialX = 0;
initialY = 0;
xOffset = 0;
yOffset = 0;
setTranslate(0, 0, dragItem);
}
active = false; //the drag is no longer active
}
function drag(e) { //when the circle is being dragged
if (active) { //if the drag is active
e.preventDefault(); //the user cant do anything else but drag
if (e.type === "touchmove") { //if its a touchscreen
currentX = e.touches[0].clientX - initialX; //set current x-cordinate to where it is now
currentY = e.touches[0].clientY - initialY; //set current y-cordinate to where it is now
} else { //if its not a touchscreen (mouse)
currentX = e.clientX - initialX; //set current x-cordinate to where it is now
currentY = e.clientY - initialY; //set current y-cordinate to where it is now
}
//Im not sure what this does but it dosnt work without it
xOffset = currentX;
yOffset = currentY;
setTranslate(currentX, currentY, dragItem);
}
}
function setTranslate(xPos, yPos, el) { //Im not sure what this does but it dosnt work without it
el.style.transform = "translate3d(" + xPos + "px, " + yPos + "px, 0)";
}
</script>
</body>
</html>
所以我的理解是，您想拖放球。当球掉到盒子外面时，它必须回到拖动位置，对吗？
为什么不使用Jquery的拖放功能？
// DRAG AND DROP Function
$("#item").draggable({ cursor: "crosshair", revert: "invalid" });
$(".box").droppable({
accept: "#item",
drop: function(event, ui) {
$(ui.draggable).detach().appendTo($(this));
}
});