Question

I’ve looked around and it seems like people say you can re-render the data after you zoom in now that you know the scale factor for UIScrollView. I’ve also seen some posts about making your layer to a CATiledLayer and set the levelsOfDetailBias and levelsOfDetail.

What I have is a UIScrollView, and in it, a ResultsView which is a subclass of UIView:

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        CATiledLayer *tiledLayer = (CATiledLayer *)self.layer;
        tiledLayer.levelsOfDetailBias = 3;
        tiledLayer.levelsOfDetail = 3;
        self.opaque = YES;
    }
    return self;
}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
}
*/

+ (Class)layerClass {
    return [CATiledLayer class];
}

In my class where I have the UIScrollView and ResultsView, I do:

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    return self.ResultsView;
}

Is this enough to have the text rerendered (sharp)? Or do I need to implement something in

 - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
 }

If so, I’m not sure how to do that. In my class with UIScrollView and ResultsView, in ResultsView (in the XIB), I just have a couple of UILabels and UIViews (UIViews used for headings/footers for the view). So I do not know how to redraw those from ResultsView. Although ResultsView has the UILabels and UIViews as children of it in the XIB, I’m not sure how I would redraw those from the ResultsView class, and what I would need to do anyway.

Or is this the wrong approach? Do I just need to resize the UILabel and UIView by the scale factor in the scrollViewDidEndZooming: delegate method? TIA

Answer 1

I think you are taking the wrong approach. If your view consists of UILabels and UIViews that do not do any custom drawing, I would not mess with using a CATiledLayer backed view. Instead implement the scrollViewDidEndZooming:withView:atScale: delegate method and do something like this:

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
    scale *= [[[self.scrollView window] screen] scale];
    [view setContentScaleFactor:scale];
    for (UIView *subview in view.subviews) {
        [subview setContentScaleFactor:scale];
    }
}