Question

I am making application for iPad, only landscape mode will be supported. I am having a UIView and later I am dynamically adding UIImageView as a subview. However my goal is to add images in centre of the UIView. So I used this code,

[imageView setCenter:dynamicMainView.center];

where imageView is UIImageView(Obvious :)) and dynamicMainView is UIView, However final outcome docent seem to be in centre,

Visual Representation

---

Full method code for adding UIImageView in UIView is,

-(void) addImageIntoMainDynamicView:(UIImage *) image
{
    [self clearImageFromMainDynamicView];//Always clear Dynamic main view before adding new views
    imageView = [[UIImageView alloc] initWithImage:image];  
        if(imageView.bounds.size.width > dynamicMainView.bounds.size.width || imageView.bounds.size.height > dynamicMainView.bounds.size.height)
        {
            [imageView setFrame:[dynamicMainView bounds]];
        }

        [imageView setCenter:dynamicMainView.center];
        NSLog(@"Image : X = %f and Y = %f", imageView.center.x,imageView.center.y );
        NSLog(@"UIView : X = %f and Y = %f", dynamicMainView.center.x,dynamicMainView.center.y );
        [dynamicMainView addSubview:imageView];
    [imageView release];
}

And above log value is,

2011-12-21 21:07:11.850 Map1TestApp[94645:11603] Image : X = 512.000000 and Y = 371.500000
2011-12-21 21:07:11.853 Map1TestApp[94645:11603] UIView : X = 512.000000 and Y = 371.500000

Any clue about why it’s not adding in centre? Am I doing something wrong?

---

FOR FUTURE VIEWER THE ANWSER WAS :

[imageView setCenter:CGPointMake(CGRectGetMidX([dynamicMainView bounds]), CGRectGetMidY([dynamicMainView bounds]))];

Answer 1

The center of a view is expressed in it’s superview’s coordinate system. So you are centering your image view in the wrong coordinate system. (dynamic view’s superview as opposed to dynamic view)

To centre view A within view B, the centre point of view A has to be the centre of the bounds rectangle of view B. You can get this using (from memory!) CGRectGetMidX and CGRectGetMidY.