Comments on: Changing the range of the zoom factor for UIWebView objects

By: Alexander

Alexander — Tue, 24 Jul 2012 12:28:42 +0000

@Eric
Putting a UIWebView into a UIScrollView is highly discouraged by Apple for good reasons. While it seems to work at first glance, there will be conflicts with the gestures.

Of course you can get the reference to the scrollview of the WebView under iOS 4 as well, but this would mean that you have to make certain assumptions about the internal view hierarchy of UIWebView (you assume that there’s a UIScrollView internally), which is strictly speaking using “private” API. You could do this with only using the public API though, by checking all subviews of UIWebView and look for the scrollview. But because Apple has not documented the internals of UIWebView, be prepared that you might not always find want you’re looking for. Use the new iOS 5 API when available to get the reference to the scrollview. This is a safe way to get access to the scroll view.

By: Eric

Eric — Tue, 24 Jul 2012 02:56:21 +0000

My app is running ios4.x and higher,I have see someone have maked it true on ios 4.x.But i don’t know how can do that. If the UIWebView have two scrollViews? After contentView zoom it can move left or right and navigationBar can down or up.

By: Alexander

Alexander — Mon, 23 Jul 2012 10:15:34 +0000

@Eric
The Navigation toolbar is not sitting within the content area of the UIWebView and therefore does not zoom with the content area. In order to get a scrolling navigation toolbar like in Safari, you can get a reference to the internal UIScrollView of the UIWebView (requires iOS 5) and then use the scrollview properties and the scrollview delegate methods to move the navigation together with the content when it is scrolled. You can also set the content offset or insets for the scrollview to initially move the content down in order to make room for the navigation toolbar, so the navigation toolbar can be placed on top of the UIWebView without overlapping the content area of the UIWebView when it is scrolled to the top.
When scrolling down, the UIScrollView delegates will be called and will tell you how much the content area is scrolled. And so you know how much you need to move the navigation toolbar out of view.

By: Eric

Eric — Mon, 23 Jul 2012 02:55:36 +0000

Hi Alexander
I have met a trouble about UIWebView ,In the mobile/safari When i zoom the contentView it became larger or smaller,but the navigationbar have no effect like this .It does not change the size by the contentView zoom or not. I want to use UIWebView to do like this I found that when i scorlled the contentView the safari’s navigationbar scolling with the contentView, and I have dumped the UIWeView’ hierarchy ,only one scrollView in UIWebView,I don’t know how to do it. Any help will appricate.

By: Alexander

Alexander — Mon, 21 Mar 2011 15:38:10 +0000

@tiantian
Basically, parsing the main HTML file for other files is what you need to do.

It is true that the iOS doesn’t use a “disk” cache, but at least the NSURLCache object is called, which is prepared to maintain a disk cache, but just doesn’t cache any files on disk.
But iCab overwrites the NSURLCache to implement its own cache which can save files on disk (this is also used for the Offline mode). So iCab usually doesn’t need to download files again.

By: tiantian

tiantian — Mon, 21 Mar 2011 14:55:04 +0000

Thanks again. I’ve successed save data into webarchive file. But the way I get all the data is too complicate. I parse all image and js element in the main html document and start a NSURLConnection for each of them. Do you have a better way to get all the data from a url including image and js? BTW, I found UIWebview never cache any data automatically, did you use any cache mechanism for save page? I see the page can be immediately saved after I tab that button even I turn wifi off.

By: Alexander

Alexander — Tue, 01 Mar 2011 13:00:11 +0000

@tiantian
If you open an existing webarchive in the properties list editor, you’ll see how this works. Basically the webarchive is a structure of NSArrays, NSDictionaries which represents the page structure with all its files. And all the files data is stored as NSData objects. So you just need to store the raw data you’ve got from the NSURLResponses together with the meta data (MIME type, URL) in the correct array/dictionary structure. And to save this structure as binary property list, you can use the NSPropertyListSerialization class.

By: tiantian

tiantian — Tue, 01 Mar 2011 02:18:41 +0000

Thanks a lot for your replay, but how to get the binary property list of a web page? I can get all the data response from a url, but the data’s format is not a binary property list type . Is there a way to convent that data to a binary property list type?

By: Alexander

Alexander — Mon, 21 Feb 2011 13:00:46 +0000

@tiantian
Technically the webarchive file format is equal to the standard binary property list file format. So the webarchives can be created using the standard NSPropertyListSerialization class.

By: tiantian

tiantian — Mon, 21 Feb 2011 03:06:08 +0000

Sorry for asking here, because I don’t know your e-mail. It’s about the web page saving feature. I wander how you save page as webarchive file? It seems Webarchive is a class in Mac os API, not in IOS . Did you use private API to do that?

By: denizen

denizen — Fri, 04 Feb 2011 22:06:00 +0000

Thanks.
The problem is, I’m surpassing the memory limit before iOS frees the cache, so the app’s being killed due to memory usage. I’m testing on a relatively low-RAM device (iPod Touch 2G, running iOS4), so it might just be an issue with iOS. I’ll try to get ahold of a bigger device and see if the problem persists.

By: Alexander

Alexander — Fri, 04 Feb 2011 12:32:26 +0000

@denizen
You can’t do anything here. The iOS seems to use a shared cache for all UIWebView objects of an App and therefore when you release one UIWebView object, this hasn’t much impact on the memory usage because of this shared caches. But the iOS should nevertheless release (parts of) the cache when your App can’t free enough memory otherwise.

By: denizen

denizen — Fri, 04 Feb 2011 06:07:52 +0000

Great post. I’m writing a little iOS browser as a side project, and I need a little advice. (this probably isn’t the right area of the site to ask it, but I couldn’t find your email)
Anyway, I’m implementing multiple tabs, each comprising one UIWebView. When I receive a memory warning, I release all non-foreground tabs. Problem is, even when I’ve released them, quite a bit of memory stays behind. I’ve verified they’re being released in instruments, and I regain a bit of memory, but not nearly all of it. What can I do about this? I’m thinking this is an issue with a cache not being released; Instruments says the leftover memory is CFData that the webview created internally. What can I do about this? Os there something I can do to manually flush the cache?

By: Thomas

Thomas — Mon, 27 Dec 2010 22:00:53 +0000

Useful information, well explained. Thank you!