Shake visual effect on iPhone (NOT shaking the device)

Question

On login failure, I\'d prefer to avoid showing an alert, it\'s too fleeting. Showing the alert and then showing the text somewhere on the login screen seems like duplication

Answer 1

This UIView category snippet worked for me. It's using 3 CABasingAnimations applied to view's layer.

#import 
#import 

#define Y_OFFSET 2.0f
#define X_OFFSET 2.0f
#define ANGLE_OFFSET (M_PI_4*0.1f)

@interface UIView (shakeAnimation)

-(BOOL)isShakeAnimationRunning;
-(void)startShakeAnimation;
-(void)stopShakeAnimation;

@end



@implementation UIView (shakeAnimation)

-(BOOL)isShakeAnimationRunning{
     return [self.layer animationForKey:@"shake_rotation"] != nil;
}

-(void)startShakeAnimation{
    CFTimeInterval offset=(double)arc4random()/(double)RAND_MAX;
    self.transform=CGAffineTransformRotate(self.transform, -ANGLE_OFFSET*0.5);
    self.transform=CGAffineTransformTranslate(self.transform, -X_OFFSET*0.5f, -Y_OFFSET*0.5f);

    CABasicAnimation *tAnim=[CABasicAnimation animationWithKeyPath:@"position.x"];
    tAnim.repeatCount=HUGE_VALF;
    tAnim.byValue=[NSNumber numberWithFloat:X_OFFSET];
    tAnim.duration=0.07f;
    tAnim.autoreverses=YES;
    tAnim.timeOffset=offset;
    [self.layer addAnimation:tAnim forKey:@"shake_translation_x"];

    CABasicAnimation *tyAnim=[CABasicAnimation animationWithKeyPath:@"position.y"];
    tyAnim.repeatCount=HUGE_VALF;
    tyAnim.byValue=[NSNumber numberWithFloat:Y_OFFSET];
    tyAnim.duration=0.06f;
    tyAnim.autoreverses=YES;
    tyAnim.timeOffset=offset;
    [self.layer addAnimation:tyAnim forKey:@"shake_translation_y"];

    CABasicAnimation *rAnim=[CABasicAnimation animationWithKeyPath:@"transform.rotation"];
    rAnim.repeatCount=HUGE_VALF;
    rAnim.byValue=[NSNumber numberWithFloat:ANGLE_OFFSET];
    rAnim.duration=0.15f;
    rAnim.autoreverses=YES;
    rAnim.timeOffset=offset;
    [self.layer addAnimation:rAnim forKey:@"shake_rotation"];
}
-(void)stopShakeAnimation{
    [self.layer removeAnimationForKey:@"shake_translation_x"];
    [self.layer removeAnimationForKey:@"shake_translation_y"];
    [self.layer removeAnimationForKey:@"shake_rotation"];
    [UIView animateWithDuration:0.2f animations:^{
        self.transform=CGAffineTransformRotate(self.transform, ANGLE_OFFSET*0.5);
        self.transform=CGAffineTransformTranslate(self.transform, X_OFFSET*0.5, Y_OFFSET*0.5f);
    }];
}

@end

Hope it helpes someone :)