事件深入应用

一、拖拽事件：onmousedown:选择元素

 onmousemove:移动元素

 onmouseup:释放元素

drag(oDiv);

        function drag(obj){  

obj.onmousedown = function(ev){

var ev = ev || event;

var disX = ev.clientX - this.offsetLeft;

var disY = ev.clientY - this.offsetTop;

//IE setCapture();

if(obj.setCapture){

obj.setCapture();

}

document.onmousemove = function(ev){

var ev = ev || event;

var Left = ev.clientX - disX;

var Top = ev.clientY - disY;

//控制在可视区内

if( Left < 50){

Left = 0;

}else if( Left >document.documentElement.clientWidth - obj.offsetWidth) {

Left = document.documentElement.clientWidth - obj.offsetWidth;

}

if( Top < 50){

Top = 0;

}else if (Top > document.documentElement.clientHeight - obj.offsetHeight){

Top = document.documentElement.clientHeight - obj.offsetHeight;

}

// 碰撞事件

var L1 = Left;

var R1 = L + obj.offsetWidth;

var T1 = Top;

var B1 = T + obj.offsetHeight;

var L2 = oImg.offsetLeft;

var R2 = L2 + oImg.offsetWidth;

var T2 = oImg.offsetTop;

var B2 = T2 + oImg.offsetHeight;

if( R1< L2 || L1 > R2 || B1 < T2 || T1 > B2){

oImg.src = '1.jpg';

}else{

oImg.src = '2.jpg';

}

obj.style.left = Left + 'px';

obj.style.top = Top + 'px';

}

document.onmouseup = function(){

document.onmousemove = document.onmousedown = null;

//全局捕获 releaseCapture();

if(obj.releaseCapture){

obj.releaseCapture();

}

}

return false;

}

}

1) 托转的时候，如果有文字被选中会出现问题

原因：当鼠标按下的时候，如果页面中有文字被选中，会触发浏览器默认拖拽文字效果

  标准：阻止默认事件

非标准： 全局捕获