Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
- Subject: Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
- From: Motti Shneor <email@hidden>
- Date: Mon, 22 Apr 2013 10:26:07 +0300
Hello everyone. I asked this several times before, but no one gave any hint -- I'd like to know if anyone here has any clue, at least where to search for an answer.
I need to observe the visible contents of a UIWebView dIsplayed in my iOS application. Each time the visible contents changes, I need to capture the contents as image, and transmit it to our server. A bit like screen-sharing on the Mac, but not for the whole screen contents, just a single view.
I already succeeded in capturing the contents of the view as an image-buffer (out of the CALAyer's context) and I can (brutally) solve my problem by setting up a timer that will sample the view's contents N times a second. However, I'd like to avoid transmitting anything when the view doesn't change, and I want to avoid comparing image-buffers N times a second (frame-differencing) on iOS devices, which is battery abuse.
I DO NOT wish to re-transmit when the user rotates his iOS device and the view rotates. However I DO want to re-transmit when the user pinches to zoom in and out, or scroll through the view's contents. Also, I do not want the whole contents transmitted. just the visible part of it. This is why I'm not sure I need to "ride" the "drawRect" thing. I'm not sure a view must redraw when it undergoes visual translation/rotation/scaling etc.
I started looking for the right delegate call, and quite soon got lost. My background is Cocoa on MacOS and iOS view/CALayer system still confuses me.
This UIWebView might have subviews I'm not aware of, and it will usually be rendering a document file (such as PDF) via a given URL.
The "right" way as I see it, is to get notified when the UIWebView decides to re-display or redraw its contents after something changes. (either content change - redrawing, or some user manipulation zoom, rotate, translate, animation).
Can anyone hint on where to start here?
I'll be grateful for any hint or direction.
Thanks.
Motti Shneor
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