Create README.md

Author: seedante

README.md

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+# CardAnimation
+[Design from Dribble](https://dribbble.com/shots/1265487-First-shot-in-Chapps-Animation)
+
+![Design from Dribble](https://d13yacurqjgara.cloudfront.net/users/32399/screenshots/1265487/attachments/173545/secret-project-animation_2x.gif)
+
+
+**Change Anchor Point of CALayer**
+
+like: (0.5, 0.5) ->(0.5, 1)
+
+Frame:
+
+There are many ways to do this: [link](http://stackoverflow.com/questions/1968017/changing-my-calayers-anchorpoint-moves-the-view)
+
+    subView.frame = frame
+    subView.layer.anchorPoint = CGPointMake(0.5, 1)
+    subView.frame = frame
+
+AutoLayout:
+
+Discussion on stackoverflow: [link](http://stackoverflow.com/questions/12943107/how-do-i-adjust-the-anchor-point-of-a-calayer-when-auto-layout-is-being-used/14105757#14105757), but I find a simple way:
+
+    let subViewHeight = 
+    let oldConstraintConstant = centerYConstraint.constant
+    subView.layer.anchorPoint = CGPointMake(0.5, 1)
+    //Like what you do with frame, you need to compensate for additional translation.
+    centerYConstraint.constant = subView.bounds.size.height/2 + oldConstraintConstant
+    
+**Transform and AutoLayout**
+
+From iOS8, transform and autolayout play nice. There is a blog for this: [Constraints & Transformations](http://revealapp.com/blog/constraints-and-transforms.html)
+
+Transform doesn't affect autolayout, only constraints can affect autolayout.
+
+Transformes affect view's frame, but do nothing to view's center and bounds.
+
+**Make flip animation background not transparent**
+
+Use a subview, and change the container view's background color to what color you want.
+
+When the container view is vertical to screen, make the subview hidden, and after the container view back, make subview visible.
+
+**Rotation Animation Bug in action method**
+
+    let flipTransform = CATransform3DRotate(CATransform3DIdentity, CGFloat(-M_PI), 1, 0, 0)
+    UIView.animateWithDuration(0.3, {
+      view.layer.transform = flipTransform
+    })
+    
+The animation will not execute and the view just change if you execute above code in an action method, like clip a button.
+You could use 'CGFloat(-M_PI) * 0.99' to fix this.
+
+**To-Do List**
+
+1. reuse card view
+
+2. reorder card view
+
+3. delete and add card view with pan gesture