如何设置可拖动 div 的起始位置？

Question

我有一个可拖动的div，只要我不通过top, right, … CSS 改变它的位置，它就可以正常工作。我的目标是将 div 的预拖动位置设置到其窗口的右上角，我使用top = 0, right = 0 完成了此操作；问题是，div 在拖动时会粘在那个位置，stretches。

dragElement(document.getElementById("myModal"));

function dragElement(elmnt) {
  var pos1 = 0, pos2 = 0, pos3 = 0, pos4 = 0;
  if (document.getElementById(elmnt.id + "header")) {
  document.getElementById(elmnt.id + "header").onmousedown = dragMouseDown;} 
  else {elmnt.onmousedown = dragMouseDown;}

  function dragMouseDown(w) {
    w = w || window.event;
    w.preventDefault();
    pos3 = w.clientX;
    pos4 = w.clientY;
    document.onmouseup = closeDragElement;
    document.onmousemove = elementDrag;}
    
  function elementDrag(w) {
    w = w || window.event;
    w.preventDefault();
    pos1 = pos3 - w.clientX;
    pos2 = pos4 - w.clientY;
    pos3 = w.clientX;
    pos4 = w.clientY;
    elmnt.style.top = (elmnt.offsetTop - pos2) + "px";
    elmnt.style.left = (elmnt.offsetLeft - pos1) + "px";}

  function closeDragElement() {
    document.onmouseup = null;
    document.onmousemove = null;}}

#myModal {
    position: absolute;
    z-index: 9;
    background-color: #f1f1f1;
    text-align: center;
    border: 1px solid #d3d3d3;
    top: 0;
    right: 0;}
#myModalheader {
    padding: 10px;
    cursor: move;
    z-index: 10;
    background-color: #2196F3;
    color: #fff;}

<div id="myModal">
  <div id="myModalheader">Click here to move</div>
  <p>Move</p><p>this</p><p>DIV</p>
</div>

有什么解决方法吗？感谢您的帮助。

Answer 1

给元素一个宽度和高度，你应该很好。

dragElement(document.getElementById("myModal"));

function dragElement(elmnt) {
  var pos1 = 0, pos2 = 0, pos3 = 0, pos4 = 0;
  if (document.getElementById(elmnt.id + "header")) {
  document.getElementById(elmnt.id + "header").onmousedown = dragMouseDown;} 
  else {elmnt.onmousedown = dragMouseDown;}

  function dragMouseDown(w) {
    w = w || window.event;
    w.preventDefault();
    pos3 = w.clientX;
    pos4 = w.clientY;
    document.onmouseup = closeDragElement;
    document.onmousemove = elementDrag;}
    
  function elementDrag(w) {
    w = w || window.event;
    w.preventDefault();
    pos1 = pos3 - w.clientX;
    pos2 = pos4 - w.clientY;
    pos3 = w.clientX;
    pos4 = w.clientY;
    elmnt.style.top = (elmnt.offsetTop - pos2) + "px";
    elmnt.style.left = (elmnt.offsetLeft - pos1) + "px";}

  function closeDragElement() {
    document.onmouseup = null;
    document.onmousemove = null;}}

#myModal {
    position: absolute;
    z-index: 9; height: 200px; width: 200px;
    background-color: #f1f1f1;
    text-align: center;
    border: 1px solid #d3d3d3;
    top: 0;
    right: 0;}
#myModalheader {
    padding: 10px;
    cursor: move;
    z-index: 10;
    background-color: #2196F3;
    color: #fff;}

<div id="myModal">
  <div id="myModalheader">Click here to move</div>
  <p>Move</p><p>this</p><p>DIV</p>
</div>

Answer 2

您也可以使用 flex box 将容器放在右侧。

#parentContainer{
    display: flex; justify-content: flex-end
}

Answer 3

我还有两个选择：

1. 根本不要使用right:0;，而是使用left:100%; width:max-content;，后跟transform: translateX(-100%);，所以它基于子元素而不是父元素进行偏移： （仅对 css 文件进行了更改）

dragElement(document.getElementById("myModal"));

function dragElement(elmnt) {
  var pos1 = 0, pos2 = 0, pos3 = 0, pos4 = 0;
  if (document.getElementById(elmnt.id + "header")) {
  document.getElementById(elmnt.id + "header").onmousedown = dragMouseDown;} 
  else {elmnt.onmousedown = dragMouseDown;}

  function dragMouseDown(w) {
    w = w || window.event;
    w.preventDefault();
    pos3 = w.clientX;
    pos4 = w.clientY;
    document.onmouseup = closeDragElement;
    document.onmousemove = elementDrag;}
    
  function elementDrag(w) {
    w = w || window.event;
    w.preventDefault();
    pos1 = pos3 - w.clientX;
    pos2 = pos4 - w.clientY;
    pos3 = w.clientX;
    pos4 = w.clientY;
    elmnt.style.top = (elmnt.offsetTop - pos2) + "px";
    elmnt.style.left = (elmnt.offsetLeft - pos1) + "px";}

  function closeDragElement() {
    document.onmouseup = null;
    document.onmousemove = null;}}

#myModal {
    position: absolute;
    z-index: 9;
    background-color: #f1f1f1;
    text-align: center;
    border: 1px solid #d3d3d3;
    top: 0;
    left: 100%;                   /**Important*/
    transform: translateX(-100%); /**Important: offsets based on the element's width and not its parent*/
    width:max-content;            /**Important: prevents element from shrinking*/
    top:0;
}
    
#myModalheader {
    padding: 10px;
    cursor: move;
    z-index: 10;
    background-color: #2196F3;
    color: #fff;
}

<div id="myModal">
  <div id="myModalheader">Click here to move</div>
  <p>Move</p><p>this</p><p>DIV</p>
</div>

1. 第二个选项是在第一次拖动时计算元素右侧的偏移量，并在拖动完成后将right:0;设置为right:auto; （仅对 javascript 文件进行了更改）

dragElement(document.getElementById("myModal"));

function dragElement(elmnt) {
  var pos1 = 0, pos2 = 0, pos3 = 0, pos4 = 0;
  if (document.getElementById(elmnt.id + "header")) {
  document.getElementById(elmnt.id + "header").onmousedown = dragMouseDown;} 
  else {elmnt.onmousedown = dragMouseDown;}

  function dragMouseDown(w) {
    w = w || window.event;
    w.preventDefault();
    pos3 = w.clientX;
    pos4 = w.clientY;
    document.onmouseup = closeDragElement;
    document.onmousemove = elementDrag;}
    
  function elementDrag(w) {
    w = w || window.event;
    w.preventDefault();
    pos1 = pos3 - w.clientX;
    pos2 = pos4 - w.clientY;
    pos3 = w.clientX;
    pos4 = w.clientY;
    //Check if a right offset exists (will only be true
    //during the first time you drag it)
    if(elmnt.style.right != null && elmnt.style.right != "auto"){
      //calculate right offset
      var offsetright = window.innerWidth-elmnt.offsetLeft-elmnt.offsetWidth;
      //add the offset to the right of the element
      elmnt.style.right = (offsetright +pos1) + "px";
    }
    //end of change
    
    elmnt.style.top = (elmnt.offsetTop - pos2) + "px";
    elmnt.style.left = (elmnt.offsetLeft - pos1) + "px";}

  function closeDragElement() {
    document.onmouseup = null;
    document.onmousemove = null;
    elmnt.style.right = "auto";
  }}

#myModal {
    position: absolute;
    z-index: 9;
    background-color: #f1f1f1;
    text-align: center;
    border: 1px solid #d3d3d3;
    top: 0;
    right: 0;}
#myModalheader {
    padding: 10px;
    cursor: move;
    z-index: 10;
    background-color: #2196F3;
    color: #fff;}

<div id="myModal">
  <div id="myModalheader">Click here to move</div>
  <p>Move</p><p>this</p><p>DIV</p>
</div>