下拉刷新修改

@@ -21,8 +21,7 @@ function PullRefresh(seclector, options) {
     var $window = $(window),
         $em,
         pullFormTop = false,
-        pullStart,
-        topOffset;
+        pullStart;
 
     $em = $(seclector);
 
@@ -34,15 +33,13 @@ function PullRefresh(seclector, options) {
         $em.height(options.height);
     }
 
-    topOffset = -$em.outerHeight();
-
     this.iScroll = new IScroll($em.get(0), {
         click: true,
         probeType: 3
     });
 
     this.iScroll.on('scrollStart', function() {
-        if (this.y >= topOffset) {
+        if (this.y === 0) {
             pullFormTop = true;
         }