Resizing UIWebView height to fit content

Question

I'm loading an HTML string of arbitrary length into a UIWebView which is then displayed in a UITableViewCell. I do not want this UIWebView to scroll independently of the UITableView so I must resize its height to fit the content.

This UITableViewCell is also collapsable, not showing the UIWebView when it's in its collapsed state.

The rub is, how do I know what this height is so that I can have heightForRowAtIndexPath return a proper value and allow the table to look and scroll correctly?

Here's some example code:

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
if (indexPath.row == 0)
    return 286;

if (indexPath.row == 1) {
    if (analysisExpanded)
        return analysisWebViewHeight + 39;
    else 
        return 52;
}

if (sourcesExpanded)
    return sourcesWebViewHeight + 39;

return 53;

}

Pretty simple. The 39 is the height of some header stuff I have in the cell with the webview.

I am loading the "expanded view" of the cell from a nib, so to get the webview I'm calling viewForTag:

        UIWebView* sourcesWebView = (UIWebView*)[cell viewWithTag:1];
        [sourcesWebView setBackgroundColor:[UIColor clearColor]];
        [sourcesWebView loadHTMLString:placeholder baseURL:[NSURL URLWithString:@"http://example.com/"]];
        sourcesWebViewHeight = [[sourcesWebView stringByEvaluatingJavaScriptFromString:@"document.documentElement.scrollHeight"] floatValue];
        [sourcesWebView setFrame:CGRectMake(sourcesWebView.frame.origin.x, sourcesWebView.frame.origin.y, sourcesWebView.frame.size.width, sourcesWebViewHeight)];

sourcesWebViewHeight is an iVar that is updated by the above code in cellForRowAtIndexPath. If the user taps the cell three times, expand-collapse-expand, and does a little scrolling, eventually it gets the correct height.

I tried "Preloading" the height by using a memory-only UIWebView object, but that never returned correct numbers for some reason.

Answer 1

The issue was that I was attempting to get the scroll size before the web view had a chance to render it.

After implementing the didFinishLoad delegate method, my original javascript worked fine to get the height.