CODEWITHSUNDEEP
objective-ciosxcodetagsuiimage
James Anderson
James Anderson

Reputation: 566

Identify UIImages Individually

I've got an app where multiple UIImages can be added to the view. Those images can then be dragged around the screen. How can I check which image has been dragged and then save that image's coordinates to a file and no other UIImage in the same view. I need a way of tagging each UIImage if possible to separate them out and identify them each individually. Hopefully this makes sense!

This is how I'm adding each UIImage to the view:

CGRect imageFrame = CGRectMake(activeView.center.x - 50, activeView.center.y - 50, 200, 200);
imageResizableView = [[SPUserResizableView alloc] initWithFrame:imageFrame];
UIImage *image = [UIImage imageNamed:@"galaxy.jpg"];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
imageResizableView.contentView = imageView;
imageResizableView.delegate = self;
[activeView addSubview:imageResizableView];

Upvotes: 0

Views: 433

Answers (3)

David Hoerl
David Hoerl

Reputation: 41642

UIImageViews are UIView subclasses, so have a tag property. Set that for each image, then when you want that one image [self.subViews viewWithTag:number]; to find it.

EDIT: If I understand this, there are many UIImageViews, but multiple imageViews may show the same image.

Assuming that, then you partition the tag's 32 bits to say 16 bits upper as the unique imageView number, and the lower 16 are the image number. You will then need to iterate through all subviews looking for the image. You can use macros to make this easier:

#define TAG_NUMBER(imageViewNum, imageNum) ((imageViewNum << 16) | imageNum)
#define IMAGE_FROM_TAG(tag) (tag & 0xFFFF)
etc

when you want to find all imageviews showing that image:

for(UIVIew *view in self.subviews) {
if(![view isKindOf:[UIIMageView class]]) continue;

int imageNum = IMAGE_FROM(view.tag);
if(imageNum == theOneIwant) {
  save frame of "view"
}
}

Upvotes: 1

Jody Hagins
Jody Hagins

Reputation: 28349

If integer tags are good enough, then use the tag property which already exists for UIViews.

However, if you want something more, you can use obj_setAssociatedObject to add a tagName property to UIView.

@interface UIView (tagName)
@property (nonatomic, copy) NSString *tagName;
@end

--

#import <objc/runtime.h>

@implementation UIView (tagName)
static char tagNameKey[1];

- (NSString*)tagName {
    return objc_getAssociatedObject(self, tagNameKey);
}

- (void)setTagName:(NSString *)tagName {
    objc_setAssociatedObject(self, tagNameKey, tagName, OBJC_ASSOCIATION_COPY_NONATOMIC);
}
@end

which can then be used like so...

NSString *imageName = @"galaxy.jpg";
UIImage *image = [UIImage imageNamed:imageName];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
imageView.tagName = imageName;

and later...

NSString *imageName = imageView.tagName;

EDIT

Of course, you can add whatever you want, for example to mimic viewWithTag

- (UIView*)viewWithTagName:(NSString *)tagName {
    if ([self.tagName isEqualToString:tagName]) {
        return self;
    }

    UIView *result = nil;
    for (UIView *view in self.subviews) {
        if ((result = [view viewWithTagName:tagName]) != nil) {
            return result;
        }
    }

    return nil;
}

Upvotes: 1

tiguero
tiguero

Reputation: 11537

You can use the tag property on UIVIew.

As per mentioned in the official doc:

tag An integer that you can use to identify view objects in your application.

@property(nonatomic) NSInteger tag Discussion The default value is 0. You can set the value of this tag and use that value to identify the view later.

Upvotes: 2

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