Question

In my program , I set replace image when I swipe for animation

cate 1.png -> cate2.png->cate3.png->cate1.png-> ~

and set changing label’s frame by using setframe.

-(void) scrollViewDidScroll:(UIScrollView *)scrollView
{
  int offsetx=(int)scrollView.contentOffset.x;

if(offsetx>0 && offsetx<20)
{

    UIImage * image=[UIImage imageNamed:@"cate1.png"];  
    cateImageview.image=image;

    UIFont * font=[UIFont systemFontOfSize:14];
    [gameLabel setFont:font];

    [gameLabel setFrame:CGRectMake(140,18,50,50)];


    return ;

}

 if(offsetx>20 && offsetx<40)
{

    UIImage * image=[UIImage imageNamed:@"cate2.png"];  
    cateImageview.image=image;

    [gameLabel setFrame:CGRectMake(122,16,50,50)];

    return ;

}
    if(offsetx>40 && offsetx<60)
    {

        UIImage * image=[UIImage imageNamed:@"cate3.png"];  
        cateImageview.image=image;

        [gameLabel setFrame:CGRectMake(113,14,50,50)];

        return ;

    }

    if( offsetx>60 && offsetx<80)
    { 
        UIImage * image=[UIImage imageNamed:@"cate1.png"];  
        cateImageview.image=image;

        [gameLabel setFrame:CGRectMake(103,12,50,50)];

        return ;

    }

   if( offsetx>80 && offsetx<100)
   {

    UIImage * image=[UIImage imageNamed:@"cate2.png"];  
    cateImageview.image=image;

    [gameLabel setFrame:CGRectMake(92,10,50,50)];

       return ;

   }

   if( offsetx>100 && offsetx<120)
   {

    UIImage * image=[UIImage imageNamed:@"cate3.png"];  
    cateImageview.image=image;

    [gameLabel setFrame:CGRectMake(83,8,50,50)];

       return ;

   }

      .
      .
      .

 if(offsetx >820 && offset <840)
      .
      .
 }

1. Do using replace image way for animation have problem? I want to know a better way.

2. Do using label’s frame way for animation have problem? I want to know a better way.

3. label.frame=CGRectMake(~,~,~,~) vs [label setFrame:CGReckMake(~,~,~,~)]
   Is there differences? what?

Answer 1

1. Animating Image

You can’t animate changing the image using the image property. If you want to fade the image between one and another you can add a second imageView on the same frame, above your imageView and animate its opacity from 0 to 1. Then when the animation finishes, remove the old imageView or change the image and remove the animated imageView.

2. Animating Frame

The frame is an animatable property but simply setting a new value won’t cause an animation. There is no problem using the frame to animate. Look into UIView animations for simple animations like this one:

[UIView animateWithDuration:yourDurationInSeconds animations:^{
    // Changing the frame in here will cause the frame to animate over the specified duration
    [label setFrame:yourNewFrame];
}];

3. Dot-notation or not

label.frame = ...; and [label setFrame:...]; is exactly the same thing. Just two different ways of writing code.