如何在javascript中为我的可拖动对象设置"边界"区域？

Question

我正在制作一个拖放JavaScript引擎.我学会了如何将边界框设置为父元素.但是,现在我希望将边界框设置为任何父级的任何父级,或者设置为整个页面(无边界).

现在我的Javascript引擎看起来像:

// JavaScript Document

var dragObj;

document.addEventListener("mousedown", down, false);

function down(event) {
    if(~event.target.className.search(/drag/)) {
        dragObj = makeObj(event.target);
        dragObj.element.style.zIndex="100";
        document.addEventListener("mousemove", freeMovement, false);
    }
}

function freeMovement(event) {

    if (typeof(dragObj.element.mouseup) == "undefined")
        document.addEventListener("mouseup", drop, false);
    //Prevents redundantly adding the same event handler repeatedly

    dragObj.element.style.left = Math.max(0, Math.min(event.clientX - dragObj.posX, dragObj.boundX)) + "px";
    dragObj.element.style.top = Math.max(0, Math.min(event.clientY - dragObj.posY, dragObj.boundY)) + "px";
}

function drop() {
    dragObj.element.style.zIndex="1";

    document.removeEventListener("mousemove", freeMovement, false);
    document.removeEventListener("mouseup", drop, false);
    //alert("DEBUG_DROP");
}

function makeBoundlessObj(e) {
    var obj = new Object();
    obj.element = e;

    obj.boundX = e.parentNode.offsetWidth - e.offsetWidth;
    obj.boundY = e.parentNode.offsetHeight - e.offsetHeight;

    obj.posX = event.clientX - e.offsetLeft;
    obj.posY = event.clientY - e.offsetTop;

    return obj;
}

function makeObj(e) {
    obj = new Object();
    obj.element = e;

    obj.boundX = e.parentNode.offsetWidth - e.offsetWidth;
    obj.boundY = e.parentNode.offsetHeight - e.offsetHeight;

    obj.posX = event.clientX - e.offsetLeft;
    obj.posY = event.clientY - e.offsetTop;

    var curleft = curtop = 0;
    if (e.offsetParent) {
        do {
            curleft += e.offsetLeft;
            curtop += e.offsetTop;
            //alert(e.id + ":" + e.innerHTML);
            if(~e.className.search(/bound/)) {
                obj.boundX = curleft - obj.element.offsetLeft;
                obj.boundY = curtop - obj.element.offsetTop;
                return obj;
            }

        } while (e = e.offsetParent);
    }

    return obj;
}

function findPos(obj) { // Donated by `lwburk` on StackOverflow
    var curleft = curtop = 0;
    if (obj.offsetParent) {
        do {
            curleft += obj.offsetLeft;
            curtop += obj.offsetTop;
        } while (obj = obj.offsetParent);
        return { x: curleft, y: curtop };
    }
}

我的CSS如下:

@charset "utf-8";
/* CSS Document */


* {
    padding: 0px;
    margin: 0px;
}

.drag {
    position: absolute;
    -webkit-user-select: none;
    -moz-user-select: none;
    user-select: none;
}

.bound {
    position: relative;
}

.square {
    width: 100px;
    height: 100px;
    background: red;
    cursor:move;
}

#center {
    width: 500px;
    height: 300px;
    margin: auto;
    margin-top: 50px;
    background-color:#ccc;
    text-align: center;
    border-radius: 25px;
    -moz-border-radius: 25px;
}

#box {
    background-color: #FF3;
    height: 278px;
    border-radius: 0 0 25px 25px;
    -moz-border-radius: 0 0 25px 25px;
    opacity: 0.5;
}

我的HTML很干净:

<div id="center">
    <h1>Hello World! <hr /></h1>
    <div id="box" class="bound">
        <p class="drag square"> One </p>
        <p class="drag square"> Two </p>
    </div>
</div>

我试图多次制作正确的功能.我会给一个我做过的不起作用的东西,我会列出原因:

1. 如果它没有边界,我将默认边界设置为父元素(因为我不知道如何将边界设置为整个页面)

2. 如果其中一个父元素是一个绑定,那么我没有正确设置绑定坐标(再次,我不知道如何)

哦,我在创建drag_object时设置了界限.

JavaScript创建功能:

function makeObj(e) {
    var obj = new Object();
    obj.element = e;

    obj.boundX = e.parentNode.offsetWidth - e.offsetWidth;
    obj.boundY = e.parentNode.offsetHeight - e.offsetHeight;

    obj.posX = event.clientX - e.offsetLeft;
    obj.posY = event.clientY - e.offsetTop;

    var curleft = curtop = 0;
    if (e.offsetParent) {
        do {
            curleft += e.offsetLeft;
            curtop += e.offsetTop;
            //alert(e.id + ":" + e.innerHTML);
            if(~e.className.search(/bound/)) {
                obj.boundX = curleft - obj.element.offsetLeft;
                obj.boundY = curtop - obj.element.offsetTop;
                return obj;
            }

        } while (e = e.offsetParent);
    }

    return obj;
}

设置边界框的正确数学是什么？为什么？我可以摆脱position: relative在.bound上课吗？我可以.drag上课position: absolute吗？我知道所有这些事情可能会极大地影响边界函数的编写方式.如果我必须选择让.drag班级或.bound班级不需要某种类型position,我会选择将.bound班级设置为任何类型的定位.

谢谢大家的阅读和帮助!它对我意义重大; 我是一名全职(寄宿)高中生,空闲时间很少= /

编辑:

我应该注意到,我正在学习Javascript-或十五小时的第十天,这取决于你如何看待它,我想在开始使用像jQuery之类的库之前学习这门语言.这个引擎是我为了知识和学习语言而为自己做的学术练习=]

Answer 1

我注意到的第一件事是你没有最小边界.你需要它来强制执行上限和下限.

设置边界框的正确数学是什么？为什么？

首先,dragObj需要考虑两个边界(适用于position: absolute):

// parentNode is our bounding box
// the minimum boundary is based on the top left corner of our container
obj.minBoundX = e.parentNode.offsetLeft;
obj.minBoundY = e.parentNode.offsetTop;

// the maximum is the bottom right corner of the container
// or.. the top left (x,y) + the height and width (h,y) - the size of the square
obj.maxBoundX = obj.minBoundX + e.parentNode.offsetWidth - e.offsetWidth;
obj.maxBoundY = obj.minBoundY + e.parentNode.offsetHeight - e.offsetHeight;

执行边界是一个简单的更新freeMovement:

dragObj.element.style.left = Math.max(dragObj.minBoundX, Math.min(event.clientX - dragObj.posX, dragObj.maxBoundX)) + "px";
dragObj.element.style.top = Math.max(dragObj.minBoundY, Math.min(event.clientY - dragObj.posY, dragObj.maxBoundY)) + "px";

我可以摆脱位置:.bound类中的相对吗？对.

我可以让.drag类不是位置:绝对吗？对.您只想将您的头寸更改为相对位置,并将计算结果考虑在内.例如,您的最小界限现在为0.

// parentNode is our bounding box
// the minimum boundary is based on the top left corner of our container
obj.minBoundX = 0;
obj.minBoundY = 0;

这是position:absolute版本的JSFiddle :http://jsfiddle.net/feWcQ/(适用于Firefox 4).我还添加了两个显示边界的小盒子.希望我的回答可以帮到你!