iphone - How do I use a UIWebView in a Table Cell?

Question

I'm building a table with some text that is HTML, so I am using a UIWebView as a subview of my custom table cells. I already ran into one problem - as I scrolled down in the table, it would take the UIWebViews a second to update. For example, I'd be viewing Cells at rows numbered 1, 2, and 3. I'd scroll down to say 8, 9, and 10. For a moment, the content of the UIWebView that was visible in cell #8 was the content from cell #1, the content in cell #9 was that from cell #2, and so on.

I learned that the problem was that UIWebViews simply render their text slowly. It was suggested to instead preload the content into the UIWebView as soon as I could instead of waiting until the table receives the cellForRowAtIndexPath. So now, I have a Domain Object which before just had the text content of the WebView - but now it actually has a reference to the UIWebView itself.

But now some of the content in the UIWebView renders, and when I scroll through the table the UIWebView shows only as a grey box. If I touch the grey box, it will actually receive the touch and update the WebView - for example if I touch a link (which I may or may not do, since the box is gray and it would be by a stroke of luck), the page that was linked to will be requested and displayed properly.

- (id)initWithFrame:(CGRect)frame reuseIdentifier:(NSString *)reuseIdentifier {
if (self = [super initWithFrame:frame reuseIdentifier:reuseIdentifier]) {
            // I suppose this isn't necessary since I am just getting it from the
            // Domain Object anyway
    content = [[UIWebView alloc] initWithFrame:CGRectZero];
    content.backgroundColor = [UIColor blackColor];
    [self addSubview:content];
    [content release];
}
return self;
}

// called by cellForRowAtIndexPath 
- (void)setMyDomainObject:(MyDomainObject*)anObject {
UIWebView *contentWebView = anObject.contentWebView;
int contentIndex = [self.subviews indexOfObject:content];
[self insertSubview:contentWebView atIndex:contentIndex];
}

Answer 1

One way to deal with this would be to use several UILabels, each with different fonts. Then strategically place them within the cell as to make them seem like contiguous text. I've seen this done in a UITableView with very good results.

Another performance problem may be that you are overiding UItableViewCell and it's init method. This almost always leads to poor performance in a UITableView. Instead just use the regular UITableViewCell instances and add subviews to it's contentView.

This has been covered extensively by Matt Gallagher's Easy Custom UITableView Drawing.

Another method described was to use Three20, which can give you styled text as well.

What you are attempting currently can't be done with UIWebview.

Preloading won't help: this would slow down the UI when UIWebviews are being rendered offscreen; you should always practice lazy loading on the iPhone.

Putting UIWebviews in a UITableView will come with a potentially unacceptable performance hit. You will need to use other means to accomplish your goal.

Unfortunately, NSAttributedString is unavailable in UIKit, which could easily solve your problem.