iPhone UIWebView width does not fit after zooming operation + UIInterfaceOrientation change

Question

I created a bare bones iPhone app with a UIWebView (Scales Page to Fit = YES, shouldAutorotateToInterfaceOrientation = YES) and loaded a webpage, e.g. https://stackoverflow.com/

Rotating the device shows that UIWebView is auto-resized to fit the width. Good.

Incorrect: Zoom into the page and zoom out. Now rotating the device shows UIWebView in a weird width in one of the orientation (if u zoom in landscape, the portrait width is weird, vice versa). This behavior is fixed only when you navigate to another page.

Correct: Load the same URL in Mobile Safari. Rotating works & the width fits regardless of the zooming exercise.

Is this a UIWebView bug (probably not)? Or is there something that needs to be done to make things "just work" like in Mobile Safari?

Answer 1

I found something that worked for me. The problem is that when uiwebview changes its orientation web contents are zoommed to fit with viewport. But zoomscale parameter of scrollview subview is not updated correctly (nor are updated minimumZoomScale nor maximumZoomScale

Then we need to do it manually at willRotateToInterfaceOrientation:

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    CGFloat ratioAspect = webview.bounds.size.width/webview.bounds.size.height;
    switch (toInterfaceOrientation) {
        case UIInterfaceOrientationPortraitUpsideDown:
        case UIInterfaceOrientationPortrait:
            // Going to Portrait mode
            for (UIScrollView *scroll in [webview subviews]) { //we get the scrollview 
                // Make sure it really is a scroll view and reset the zoom scale.
                if ([scroll respondsToSelector:@selector(setZoomScale:)]){
                    scroll.minimumZoomScale = scroll.minimumZoomScale/ratioAspect;
                    scroll.maximumZoomScale = scroll.maximumZoomScale/ratioAspect;
                    [scroll setZoomScale:(scroll.zoomScale/ratioAspect) animated:YES];
                }
            }
            break;
        default:
            // Going to Landscape mode
            for (UIScrollView *scroll in [webview subviews]) { //we get the scrollview 
                // Make sure it really is a scroll view and reset the zoom scale.
                if ([scroll respondsToSelector:@selector(setZoomScale:)]){
                    scroll.minimumZoomScale = scroll.minimumZoomScale *ratioAspect;
                    scroll.maximumZoomScale = scroll.maximumZoomScale *ratioAspect;
                    [scroll setZoomScale:(scroll.zoomScale*ratioAspect) animated:YES];
                }
            }
            break;
    }
}

Hope this helps!

Answer 2

I've tried the solution from M Penades and this seems to work for me as well.

The only issue that I'm experiencing is that when running this on a 3Gs the rotation is unfortunately not very smooth.

I'm therefore now using a different approach:

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {

[super didRotateFromInterfaceOrientation:fromInterfaceOrientation];

CGFloat scale = browserWebView.contentScaleFactor;
NSString *javaStuff = [NSString stringWithFormat:@"document.body.style.zoom = %f;", scale];
[browserWebView stringByEvaluatingJavaScriptFromString:javaStuff];

}

Best Regards,
Ralph

Answer 3

- (UIScrollView *)findScrollViewInsideView:(UIView *)view
{
    for(UIView *subview in view.subviews){
        if([subview isKindOfClass:[UIScrollView class]]){
            return (UIScrollView *)subview;
        }

        UIScrollView *foundScrollView = [self findScrollViewInsideView:subview];
        if (foundScrollView){
            return foundScrollView;
        }
    }

    return nil;
}

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation
{
    switch (self.interfaceOrientation){
        case UIInterfaceOrientationLandscapeLeft:
        case UIInterfaceOrientationLandscapeRight:
        {
            UIScrollView *webViewScrollView = ([self.webView respondsToSelector:@selector(scrollView)])
                ? self.webView.scrollView
                : [self findScrollViewInsideView:self.webView];

            [webViewScrollView setZoomScale:1.01f animated:YES];
        }
            break;

        default:
            break;
    }
}

try this code, it insignificantly changes zoom level (1.01) to allow UIWebView increase content size in landscape mode

findScrollViewInsideView: method added to support ios4