UIView animation completion block not called when animation is interrupted

Question

I'm trying to call a method whenever this animation ends but in some occasions for example, when user leaves the app, its completion block never gets called. Also when a VC appears with its animation at the same time as the UIView animation, the completion block never gets called.

What should I do to make sure the callback is called even if the animation is interrupted somehow? Should I not use UIView animation completion block at all and use something else instead? Please enlighten me..!

-(void)action {

[UIView animateWithDuration:0.3
                      delay:0.0
                    options:UIViewAnimationOptionCurveEaseOut
                 animations:^{

                     self.doorLeft.frame = CGRectMake(0, 0, self.doorLeft.frame.size.width, self.doorLeft.frame.size.height);
                     self.doorRight.frame = CGRectMake(self.frame.size.width -self.doorRight.frame.size.width, 0, self.doorRight.frame.size.width, self.doorRight.frame.size.height);

                 } completion:^(BOOL finished){
                     if (finished) {
                         switch (self.type) {
                             case 0:
                                 [self.delegate startTOship];
                                 break;
                             case 1:
                                 [self.delegate gameTOship];
                                 break;
                             case 2:
                                 [self.delegate shipTOgame];
                                 break;
                             case 3:
                                 [self.delegate shipTOmap];
                                 break;
                             case 4:
                                 [self.delegate gameTOmap];
                                 break;
                             case 5:
                                 [self.delegate mapTOgame];
                                 break;
                             case 6:
                                 [self.delegate mapTOship];
                                 break;
                         }

                         [UIView animateWithDuration:0.3
                                               delay:0.5
                                             options:UIViewAnimationOptionCurveEaseOut
                                          animations:^{

                                              self.doorLeft.frame = CGRectMake(-self.doorLeft.frame.size.width, 0, self.doorLeft.frame.size.width, self.doorLeft.frame.size.height);
                                              self.doorRight.frame = CGRectMake(self.doorRight.frame.size.width *2, 0, self.doorRight.frame.size.width, self.doorRight.frame.size.height);

                                          } completion:^(BOOL finished){
                                              if (finished) {

                                                  [self actionEnded];
                                              }
                                          }
                          ];
                     }
                 }
 ];}

Robert J. Clegg Robert J. Clegg · Accepted Answer · 2016-04-07T10:50:47

What you can do, is use CATransaction instead.

[CATransaction begin];

[CATransaction setCompletionBlock:^{
    [self actionEnded]
}];

[UIView animateWithDuration:8.3 delay:0.5 options:UIViewAnimationOptionCurveEaseOut animations:^{

    self.doorLeft.frame = CGRectMake(-self.doorLeft.frame.size.width, 0, self.doorLeft.frame.size.width, self.doorLeft.frame.size.height);
    self.doorRight.frame = CGRectMake(self.doorRight.frame.size.width *2, 0, self.doorRight.frame.size.width, self.doorRight.frame.size.height);

} completion:nil];

[CATransaction commit];

If the animation is interrupted at all, the completion block is called almost immediately The block is also called when animation completes uninterrupted.

P.S: CATransaction works with all UIView animations. As long as you say begin before the animation happens and commit after the animation code.

UIView animation completion block not called when animation is interrupted

1 Answers