Fix bug that when view is not loaded or not attached to a window, the…

… CA animation completion callback is immediately called.

ios/sdk/WeexSDK/Sources/Module/WXAnimationModule.m

@@ -355,28 +355,53 @@ - (void)transitionWithArgs:(NSDictionary *)args withProperty:(NSString *)propert
 
 - (void)animation:(WXComponent *)targetComponent args:(NSDictionary *)args callback:(WXModuleKeepAliveCallback)callback
 {
+    /* Check if view of targetComponent is created, if not, we do not do animation and
+     simulate delay of 'duration' and callback.
+     For a view in list, the view migth be recycled, and if view is not attached to a window,
+     the CATransaction completion block will be called immediately, which may cause CPU overload
+     problem if JS code do any logic in the completion callback.
+     */
+
+    BOOL shouldDoAnimation = NO;
+    if ([targetComponent isViewLoaded]) {
+        UIView* view = targetComponent.view;
+        if ([view window] != nil) {
+            shouldDoAnimation = YES;
+        }
+    }
+
     /**
        UIView-style animation functions support the standard timing functions,
        but they don’t allow you to specify your own cubic Bézier curve. 
        CATransaction can be used instead to force these animations to use the supplied CAMediaTimingFunction to pace animations.
      **/
     [CATransaction begin];
     [CATransaction setAnimationTimingFunction:[WXConvert CAMediaTimingFunction:args[@"timingFunction"]]];
-    [CATransaction setCompletionBlock:^{
-        if (callback) {
-            NSDictionary *message;
-            if (_isAnimationedSuccess) {
-                message = @{@"result":@"Success",
-                            @"message":@"Success"};
-            }
-            else
-            {
-                message = @{@"result":@"Fail",
-                            @"message":@"Animation did not complete"};
+
+    if (shouldDoAnimation) {
+        [CATransaction setCompletionBlock:^{
+            if (callback) {
+                NSDictionary *message;
+                if (_isAnimationedSuccess) {
+                    message = @{@"result":@"Success",
+                                @"message":@"Success"};
+                }
+                else
+                {
+                    message = @{@"result":@"Fail",
+                                @"message":@"Animation did not complete"};
+                }
+                callback(message, NO);
             }
-            callback(message,NO);
-        }
-    }];
+        }];
+    }
+    else if (callback) {
+        double duration = [[args objectForKey:@"duration"] doubleValue] / 1000.f;
+        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(duration * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
+            callback(@{@"result":@"Success",
+                       @"message":@"Success"}, NO);
+        });
+    }
 
     BOOL needLayout = NO;
     WXTransition* transition = nil;
@@ -387,6 +412,7 @@ - (void)animation:(WXComponent *)targetComponent args:(NSDictionary *)args callb
     }
 
     [CATransaction commit];
+
     if (needLayout && transition) {
         WXPerformBlockOnComponentThread(^{
             [transition _handleTransitionWithStyles:transitionDic resetStyles:nil target:targetComponent];