iOS動畫實現：彈簧效果

源碼地址：https://github.com/thermogl/TISpringLoadedViews,

這個比較複雜，我寫了個簡化版的：

https://www.dropbox.com/s/sv3yhm8dovh0adq/SpringDemo.zip

- ()simulateSpringWithDisplayLink:(CADisplayLink * (springEnabled && != CGPointMake(self.center.x --        CGPoint kx = CGPointMake(springConstant * displacement.x, springConstant *        CGPoint bv = CGPointMake(dampingCoefficient    * velocity.x, dampingCoefficient *        CGPoint acceleration = CGPointMake((kx.x + bv.x) / mass, (kx.y + bv.y) /-= (acceleration.x *-= (acceleration.y *        CGPoint newCenter =+= (velocity.x *+= (velocity.y *

這個方法由CADisplayLink負責調用，每秒鐘預設60次。要看懂這段代碼，首先你要瞭解彈簧的原理，比如拉起彈簧收到的力怎麼計算，往回彈收到的阻力怎麼計算。

 

下面是手勢操作的代碼，也就是拖動時觸發的方法：

- ()viewWasPanned:(UIPanGestureRecognizer *== CGPointMake(self.center.x + translation.x, self.center.y + (translation.x >  && (translatedCenter.x - restCenter.x) >-= (translatedCenter.x - restCenter.x) -  (translation.x <  && (restCenter.x - translatedCenter.x) >+= (restCenter.x - translatedCenter.x) - (translation.y >  && (translatedCenter.y - restCenter.y) >-= (translatedCenter.y - restCenter.y) -  (translation.y <  && (restCenter.y - translatedCenter.y) >+= (restCenter.y - translatedCenter.y) -+ translation.x, self.center.y +