iphone - iOS translation and scale animation

Question

I'm working on UIButton animation where:

The UIButton is set in the bottom center of the screen and scaled to a small size

_menuBtn.transform = CGAffineTransformMakeScale(0.1f, 0.1f);

When the app starts it should be moving to the bottom left side of the screen as it scales or grow to its original size.

- (void)viewDidLoad
{
    [super viewDidLoad];

    _menuBtn.frame = CGRectMake(160, 513, 30, 30); 
    _menuBtn.superview.frame = CGRectMake(160, 513, 30, 30);

    _menuBtn.transform = CGAffineTransformMakeScale(0.1f, 0.1f);
    NSLog(@"_menuBtn: %@ ; _menuBtn.superview: %@", _menuBtn, _menuBtn.superview);
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDuration:5];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
    CGAffineTransform scaleTrans  = CGAffineTransformMakeScale(1.0f, 1.0f);
    CGAffineTransform lefttorightTrans  = CGAffineTransformMakeTranslation(-200.0f,0.0f);
    _menuBtn.transform = CGAffineTransformConcat(scaleTrans, lefttorightTrans);
    [UIView commitAnimations];

}

problem

When the animation starts the button starts moving from the bottom right side of the screen and not in the bottom center where it is and should be. Any help ?

Log Result

NSLog(@"%@", _myBtn);

2013-08-14 09:22:38.913 GJCoolNavi[339:c07] <UIButton: 0x813ea30; frame = (0 0; 0 0); opaque = NO; autoresize = TM+BM; layer = <CALayer: 0x813eaf0>>

thats before doing the animation...and the result after the animation is:

2013-08-14 09:30:25.719 GJCoolNavi[612:c07] <UIButton: 0x71206d0; frame = (160 294; 0 0); opaque = NO; autoresize = TM+BM; animations = { transform=<CABasicAnimation: 0x7536a80>; position=<CABasicAnimation: 0x7537dd0>; }; layer = <CALayer: 0x7120790>>

Answer 1

Why don't you do this...

_menuBtn.transform = CGAffineTransformMakeScale(0.1, 0.1);

[UIView animateWithDuration:5.0
options:UIViewAnimationOptionCurveEaseOut
animations:^(){
    _menuBtn.transform = CGAffineTransformMakeScale(1.0, 1.0);
    _menuBtn.center = self.view.center;
}
completion:nil];

I'd avoid moving stuff using a transform. Change the frame instead.

EDIT

- (void)viewDidLoad
{
    [super viewDidLoad];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    // for convenience I'm pulling these values out in to variables.
    float buttonWidth = _menuBtn.frame.size.width;
    float buttonHeight = _menuBtn.frame.size.height;
    float viewWidth = self.view.frame.size.width;
    float viewHeight = self.view.frame.size.height;

    // set the button frame to be the bottom center
    // note you shouldn't have to do this as Interface Builder should already place it there.
    // place the button in the horizontal center and 20 points from the bottom of the view.
    _menuBtn.frame = CGRectMake((viewWidth - buttonWidth) * 0.5, viewHeight - buttonHeight - 20, buttonWidth, buttonHeight);

    // scale the button down before the animation...
    _menuBtn.transform = CGAffineTransformMakeScale(0.1, 0.1);

    // now animate the view...
    [UIView animateWithDuration:5.0
                          delay:0.0
                        options:UIViewAnimationOptionCurveEaseOut
                     animations:^{
                         _menuBtn.transform = CGAffineTransformIdentity;
                         _menuBtn.frame = CGRectMake(viewWidth - buttonWidth - 20, viewHeight - buttonHeight - 20, buttonWidth, buttonHeight);
                     }
                     completion:nil];
}

Try this and let me know what happens.