Fix collection animation problem

Remove collection animation when beginRefreshing

MJRefresh.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = "MJRefresh"
-  s.version      = "1.4.0"
+  s.version      = "1.4.1"
   s.summary      = "The easiest way to use pull-to-refresh"
   s.homepage     = "https://github.com/CoderMJLee/MJRefresh"
   s.license      = "MIT"

MJRefreshExample/MJRefreshExample/MJRefresh/MJRefreshHeader.h

@@ -17,6 +17,8 @@ typedef enum {
     MJRefreshHeaderStatePulling,
     /** 正在刷新中的状态 */
     MJRefreshHeaderStateRefreshing,
+    /** 即将刷新的状态 */
+    MJRefreshHeaderStateWillRefresh
 } MJRefreshHeaderState;
 
 @interface MJRefreshHeader : MJRefreshComponent

MJRefreshExample/MJRefreshExample/MJRefresh/MJRefreshHeader.m

@@ -82,6 +82,13 @@
     }
 }
 
+- (void)drawRect:(CGRect)rect
+{
+    if (self.state == MJRefreshHeaderStateWillRefresh) {
+        self.state = MJRefreshHeaderStateRefreshing;
+    }
+}
+
 - (void)layoutSubviews
 {
     [super layoutSubviews];
@@ -219,7 +226,11 @@
 
 - (void)beginRefreshing
 {
-    self.state = MJRefreshHeaderStateRefreshing;
+    if (self.window) {
+        self.state = MJRefreshHeaderStateRefreshing;
+    } else {
+        self.state = MJRefreshHeaderStateWillRefresh;
+    }
 }
 
 - (void)endRefreshing