如果在didMoveToSuperview中使用，则UIImage + Retina4类别不起作用

Question

I'm using this UIImage category to automatically find the correct asset if the app's running on a retina 4 device: http://www.sourcedrop.net/FY53a14b0127f

It correctly finds the asset with the -568h@2x suffix if the UIImage is instantiated in a UIView subclass's init method:

-(id) init{
    self = [super init];
    if(self){
        myButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [myButton setImage:[UIImage imageNamed:@"go_back_image"] forState:UIControlStateNormal];
        [self addSubview:myButton];
    }
}

but if the UIImage is instantiated in the class's didMoveToSuperView then the category doesn't pick up the asset:

-(void)didMoveToSuperview{
    if(self.superview != nil){
            [myButton setImage:[UIImage imageNamed:@"otherImage"] forState:UIControlStateNormal];
            [myButton setImage:[UIImage imageNamed:@"otherImageHighlighted"] forState:UIControlStateHighlighted];
    }
}

If the UIImage is created in didMoveToSuperview then the normal size asset is shown...

Any thoughts?

Answer 1

Try working with breakpoints in the category code.

I had an issue where an image wasn't picked because I set an image as @"someImage.png" like

[myButton setImage:[UIImage imageNamed:@"someImage.png"] forState:UIControlStateNormal];

instead of simply "someImage" like so

[myButton setImage:[UIImage imageNamed:@"someImage"] forState:UIControlStateNormal];

Found this was the issue by debugging in the category class and used this one line to fix:

//removing png extension, if present
imageNameMutable = (NSMutableString *)[imageNameMutable stringByDeletingPathExtension];
NSString *imagePath = [[NSBundle mainBundle] pathForResource:imageNameMutable ofType:@"png"];

You might have to do something similar. Best of luck :)