javascript——拖拽原理小实例

CSS代码:

#div1{ width: 100px; height: 100px; background: green; position: absolute;}

HTML代码:

<div id="div1"></div>

JS代码:

/*
        onmousedown : 选择元素
        onmousemove : 移动元素
        onmouseup     : 释放元素
    */
    window.onload = function(){

        var oDiv = document.getElementById('div1');

        //鼠标按下时
        oDiv.onmousedown = function(ev){

            var ev = ev || event;

            // 获取鼠标点击时的距离位置
            var disX = ev.clientX - this.offsetLeft;
            var disY = ev.clientY - this.offsetTop ;

            //鼠标移动时
            document.onmousemove = function(ev){

                var ev = ev || event;

                oDiv.style.left = ev.clientX - disX + 'px';
                oDiv.style.top = ev.clientY - disY + 'px';
            };
            //鼠标释放时
            document.onmouseup = function(){
                document.onmousemove = document.onmouseup = null;
            }
        };

    };

  JS-demo2:

window.onload = function(){
        /*
            1.拖拽的时候,如果有文字被选中,会产生问题
            原因:当鼠标按下的时候,如果页面中有文字被选中,那么会触发浏览器默认拖拽文字的效果
            解决:
                标准:阻止默认行为
                非标准ie:全局捕获
        */
        var oDiv = document.getElementById('div1');

        oDiv.onmousedown = function(ev){

            var ev = ev || event;

            var disX = ev.clientX - this.offsetLeft;
            var disY = ev.clientY - this.offsetTop;

            if(oDiv.setCapture){
                oDiv.setCapture();
            }

            document.onmousemove = function(ev){

                var ev = ev || event;

                oDiv.style.left = ev.clientX - disX + 'px';
                oDiv.style.top = ev.clientY - disY + 'px';
            };

            document.onmouseup = function(){

                document.onmousemove = document.onmouseup = null;

                if(oDiv.releaseCapture){
                    oDiv.releaseCapture();
                }
                return false;
            };

        };

    };

 

posted @ 2015-03-23 16:59  波克比520  阅读(153)  评论(0编辑  收藏  举报