修改在scrollview有偏移量时刷新内容位置不正确的问题 (#1293)

MJRefresh/Base/MJRefreshComponent.m

@@ -55,13 +55,14 @@ - (void)willMoveToSuperview:(UIView *)newSuperview
     [self removeObservers];
     
     if (newSuperview) { // 新的父控件
+        // 记录UIScrollView
+        _scrollView = (UIScrollView *)newSuperview;
+        
         // 设置宽度
-        self.mj_w = newSuperview.mj_w;
+        self.mj_w = _scrollView.mj_w;
         // 设置位置
         self.mj_x = -_scrollView.mj_insetL;
-        
-        // 记录UIScrollView
-        _scrollView = (UIScrollView *)newSuperview;
+    
         // 设置永远支持垂直弹簧效果
         _scrollView.alwaysBounceVertical = YES;
         // 记录UIScrollView最开始的contentInset