affine translation prevents CGPoint relocation

Question

I expanded and moved a label (instructionLabel), then returned it to its original size but left it in the new position.

 [UIView animateWithDuration:0.5   
                  animations:^{
                      CGAffineTransform scale = CGAffineTransformMakeScale(2.0, 2.0);
                      CGAffineTransform translate = CGAffineTransformMakeTranslation(0.0, -70.0); // up 70
                      self.instructionsLabel.transform = CGAffineTransformConcat(scale,translate);
                  }
                  completion:^(BOOL finished) {
                      [UIView animateWithDuration:0.25
                                       animations:^{
                                           CGAffineTransform scale = CGAffineTransformMakeScale(1.0,1.0);
                                           CGAffineTransform translate = CGAffineTransformMakeTranslation(0,-70.0); //left in place up 70
                                           self.instructionsLabel.transform = CGAffineTransformConcat(scale, translate);
                                       }
                                       completion:^(BOOL finished) {}
                      ];

Later, I explicitly use CGPointMake to put the label back in its original spot, but it remains in the translated position (70 pts up from its original place).

instructionsLabel.frame = CGRectMake(384, 601, 655, 40);
//Adding this doesn't make any difference, in or out.

instructionsLabel.center=CGPointMake(384, 601);

I have verified by Breaks and NSLog that the CGPointMake and CGRectMake statements are reached...they just don't work after that affine transformation. Does anyone know why? (I don't want to move the label back immediately after the translation routine, but I might have to if I can't figure out why the CGPointMake routine doesn't do it.)

Thanks for any suggestions. -Rob

score 1 · Accepted Answer · answered Apr 25 '12 at 18:21

Unless Im mistaken one of the major reason for using affine transform to scale, move etc views is that, that you can later set transform to CGAffineTransformIdentity this will cancel out any transforms you have applied. I believe that your problem here is that you are setting center to what ever position it of before you applied translate transform. View indeed moves to that point + whatever transform is applied to that view. So just set transform identity.

affine translation prevents CGPoint relocation

1 Answers1