动画上的居中元素

Question

我正在开发一个简单的应用程序，它可以在选定的正方形内移动一个圆，首先你必须选择需要移动的圆，并选择它应该在的正方形，移动元素是可以的，我的问题是，即使在动画之后，元素在制作动画时也没有居中。

希望你能帮助我。

谢谢。

var selectedCircle = null;
$(".circle").click(function() {
$(this).addClass('selected').siblings().removeClass('selected').animate({ top: 0, left: 0 });
selectedCircle = $(this);
});
$(".container .square").click(function() {
if (selectedCircle) {
var selectedSquare = $(this);
selectedSquare.addClass("selected");
// 2.5 is for centering the circle in the square : width/height of square - width/height of circle / 2
// => (50 - 45) / 2
selectedCircle.animate({
top: selectedSquare.offset().top - selectedCircle.offset().top + 2.5,      
left: selectedSquare.offset().left - selectedCircle.offset().left + 2.5
}, 1200);
}
selectedCircle = null;
});

.container{
height: 200px;
width: 550px;
background-color: #eee;
padding: 10px;
position: relative;
border: 1px solid #DDD;
}
.round{
position: absolute;
bottom: 10px;
}
.square{
cursor: pointer;
display: inline-block;
width: 50px;
height: 50px;
border: 1px solid #f60;
position: relative;
}
.square:nth-child(2){
width: 65px;
}
.square:nth-child(3){
width: 75px;
}
.square:nth-child(4){
width: 85px;
}
.square:nth-child(5){
width: 95px;
}
.square:nth-child(6){
width: 105px;
}
.square:nth-child(7){
width: 115px;
}
.square:nth-child(8){
width: 125px;
}
.square .circle{
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
margin: auto;
}
.circle{
cursor: pointer;
display: inline-block;
width: 45px;
height: 45px;
border: 1px solid green;
border-radius: 100px;
text-align: center;
position: relative;
}
.circle span{
width: 10px;
height: 20px;
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
margin: auto;
}
.circle.selected{
background-color: #FFFF;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="container">
<div class="box">
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
</div>
<div class="round">
<div class="circle">
<span>1</span>
</div>
<div class="circle">
<span>2</span>
</div>
<div class="circle">
<span>3</span>
</div>
<div class="circle">
<span>4</span>
</div>
</div>
</div>

Answer 1

您的代码中注释了正确的计算：

width/height of square - width/height of circle / 2

您只需要执行该计算，而不是对2.5:进行硬编码

var xOffset = (selectedSquare.width() - selectedCircle.width()) / 2;
var yOffset = (selectedSquare.height() - selectedCircle.height()) / 2;

var selectedCircle = null;
$(".circle").click(function() {
$(this).addClass('selected').siblings().removeClass('selected').animate({ top: 0, left: 0 });
selectedCircle = $(this);
});
$(".container .square").click(function() {
if (selectedCircle) {
var selectedSquare = $(this);
selectedSquare.addClass("selected");
var xOffset = (selectedSquare.width() - selectedCircle.width()) / 2;
var yOffset = (selectedSquare.height() - selectedCircle.height()) / 2;
selectedCircle.animate({
top: selectedSquare.offset().top - selectedCircle.offset().top + yOffset,      
left: selectedSquare.offset().left - selectedCircle.offset().left + xOffset
}, 1200);
}
selectedCircle = null;
});

.container{
height: 200px;
width: 550px;
background-color: #eee;
padding: 10px;
position: relative;
border: 1px solid #DDD;
}
.round{
position: absolute;
bottom: 10px;
}
.square{
cursor: pointer;
display: inline-block;
width: 50px;
height: 50px;
border: 1px solid #f60;
position: relative;
}
.square:nth-child(2){
width: 65px;
}
.square:nth-child(3){
width: 75px;
}
.square:nth-child(4){
width: 85px;
}
.square:nth-child(5){
width: 95px;
}
.square:nth-child(6){
width: 105px;
}
.square:nth-child(7){
width: 115px;
}
.square:nth-child(8){
width: 125px;
}
.square .circle{
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
margin: auto;
}
.circle{
cursor: pointer;
display: inline-block;
width: 45px;
height: 45px;
border: 1px solid green;
border-radius: 100px;
text-align: center;
position: relative;
}
.circle span{
width: 10px;
height: 20px;
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
margin: auto;
}
.circle.selected{
background-color: #FFFF;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="container">
<div class="box">
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
<div class="square"></div>
</div>
<div class="round">
<div class="circle">
<span>1</span>
</div>
<div class="circle">
<span>2</span>
</div>
<div class="circle">
<span>3</span>
</div>
<div class="circle">
<span>4</span>
</div>
</div>
</div>