How to determine UIWebView height based on content, within a variable height UITableView?

Question

I am trying to create a UITableView with variable height rows as explained in the answer to this question

My problem is each cell contains a UIWebView with different (statically loaded) content I can't figure out how to calculate the proper height based on the content. Is there a way to do this? I've tried things like this:

   (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
       WebViewCell *cell = (WebViewCell*)[self tableView:tableView cellForRowAtIndexPath:indexPath];
       [cell setNeedsLayout];
       [cell layoutIfNeeded];
       return cell.bounds.size.height;
    }

The cells themselves are loaded from a nib, which is simply a UITableViewCell containing a UIWebView. (It would also be fine if the cells just adjusted themselves to the largest of the html content, though variable height would be nicer).

Solution 1

This code is probably too slow for table view use, but does the trick. It doesn't look like there's any alternative, as UIWebView offers no direct access to the DOM.

In a view controller's viewDidLoad I load some HTML in a webview and when the load is finished run some javascript to return the element height.

- (void)viewDidLoad
{
    [super viewDidLoad];
    webview.delegate = self;
    [webview loadHTMLString:@"<div id='foo' style='background: red'>The quick brown fox jumped over the lazy dog.</div>" baseURL:nil];
}

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    NSString *output = [webview stringByEvaluatingJavaScriptFromString:@"document.getElementById(\"foo\").offsetHeight;"];
    NSLog(@"height: %@", output);
}

Solution 2

I was very glad to find your answers, the javascript trick worked well for me.

However, I wanted to say that there is also the "sizeThatFits:" method :

CGSize goodSize = [webView sizeThatFits:CGSizeMake(anyWidth,anyHeigth)];

We have to set a preferred size different from zero, but apart from that, it usually always works !

Usually, because with the UIWebViews, it seems to work only on the second loading (I use the "loadHTMLString:" method, and yes I call "sizeThatFits:" from the delegate "didFinishLoad:" method).

So, that's why I was very happy to find your solution which works in any case.

Solution 3

This seems to work. For now.

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    CGFloat webViewHeight = 0.0f;
    if (self.subviews.count > 0) {
        UIView *scrollerView = [self.subviews objectAtIndex:0];
        if (scrollerView.subviews.count > 0) {
            UIView *webDocView = scrollerView.subviews.lastObject;
            if ([webDocView isKindOfClass:[NSClassFromString(@"UIWebDocumentView") class]])
                webViewHeight = webDocView.frame.size.height;
        }
    }
}

It should safely return 0 if it fails.

Solution 4

The better approach is to use scrollView.contentSize.height property, like below.

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
     NSLog(@"%f",webView.scrollView.contentSize.height);   
}

Solution 5

The problem with -sizeThatFits: is that it doesn't work out of the box, at least not on iOS 4.1. It just returns the current size of the webView (no matter whether it's called with CGSizeZero or an arbitrary non-zero size).

I found out that it actually works if you reduce the frame height of the webView prior to calling -sizeThatFits:.

See my solution: How to determine the content size of a UIWebView?

View more solutions

Comments

[frankodwyer]

Sounds like it can be made work, however I've tried this in the table view and it returns an empty string (I guess because the webview had not finished loading). I'm thinking I could precompute this with an offscreen webview perhaps and cache the results for the tableview.

[Erik B]

How is this better than: [webview stringByEvaluatingJavaScriptFromString:@"document.getElement‌​ById(\"foo\").offset‌​Height;"];? The problem is that the webview can't return its size until it has finished loading, which it might not have when the table needs to know its size.

[Erik B]

This is almost exactly what I do. Although I am having a problem with the fact that the webview can't return its size until it has finished loading, which it might not have when the table needs to know its size. Does anyone have an idea of how to solve this?

[BadPirate]

I used instead: NSString *output = [webView stringByEvaluatingJavaScriptFromString:@"document.body.scrol‌​lHeight;"];

[Ortwin Gentz]

@Shade: See my answer how to make this work on newer iOS versions.

[Shade]

thank you for the pointer. I did see your solution when I had this problem, but it doesn't work any better in my case. I don't really remember what I needed this for, but I did it in a different way in the end.

[Dirty Henry]

With iOS 4.3 I had to do the following : the a tiny height for my webView (ie 1px) and do the call recommended by BadPirate and adjust both the scroll view's content value and the web view's frame value afterwards.

[beetstra]

In my case it was not so much the CSS that was loaded late, but more specifically a font-file in the CSS.

[Stan]

That works! Thanks, I used before approach with javascript, but this one works better for me.

[Vadoff]

You must set the height of the initial UIWebView to at least 1px, otherwise when making the JS call you'll get the screen height returned instead.

[Andrey Gordeev]

BE CAREFUL with this answer! Sometimes it returns wrong height! I'm getting wrong value when use it with many images

[Itachi]

For me, it's scrollView.contentSize.height - CGRectGetHeight(scrollView.frame). stackoverflow.com/a/39386880/1677041