弹性动画

-(CAMediaTimingFunction*) GetTiming:(NSString*) name
{
    return [CAMediaTimingFunction functionWithName:name];
}
- (void)showLeftLoweAnimation
{
// UIBezierPath *trackPath = [UIBezierPath bezierPath];
// [trackPath moveToPoint:self.leftLowView.center];
 CGFloat y;
 if (finsh == NO)
 {
  finsh =YES;
  y = 150;
 }
 else {
  y = -1;
 }
// CGFloat y =self.leftLowView.frame.origin.y+self.leftLowScrollView.frame.size.height;
 
 CAKeyframeAnimation * animation; 
    animation = [CAKeyframeAnimation animationWithKeyPath:@"position.y"]; 
    animation.duration = 2.0; 
    animation.removedOnCompletion = NO;
    animation.fillMode = kCAFillModeForwards;
 
    NSMutableArray *values = [NSMutableArray array];
    NSMutableArray *timings = [NSMutableArray array];
    NSMutableArray *keytimes = [NSMutableArray array];
 
    //Start
    [values addObject:[NSNumber numberWithFloat:0.0]];
//    [timings addObject:[self GetTiming:kCAMediaTimingFunctionEaseIn ]];
    [keytimes addObject:[NSNumber numberWithFloat:0.0]];
 
    //Drop down
    [values addObject:[NSNumber numberWithFloat:y]];
//    [timings addObject:[self GetTiming:kCAMediaTimingFunctionEaseOut]];
    [keytimes addObject:[NSNumber numberWithFloat:0.7]];
 
    // bounce up
    [values addObject:[NSNumber numberWithFloat:0.8 * y]];
//    [timings addObject:[self GetTiming:kCAMediaTimingFunctionEaseIn]];
    [keytimes addObject:[NSNumber numberWithFloat:0.8]];
 
    // fihish down
    [values addObject:[NSNumber numberWithFloat:y]];
    [keytimes addObject:[NSNumber numberWithFloat:1.0]];
    //[timings addObject:GetTiming(kCAMediaTimingFunctionEaseIn)];
 

    animation.values = values;
    animation.timingFunctions = timings;
    animation.keyTimes = keytimes;
 
    [self.leftLowView.layer addAnimation:animation forKey:nil];   
 
//    [CATransaction commit];
}