If you can require iPhone OS 3.0 then you can experiment with the
CAShapeLayer which will automatically rerender when zoomed.
--
David Duncan @ My iPhone
On Aug 17, 2009, at 4:18 PM, Kaspar Fischer
<kaspar.fisc...@dreizak.com> wrote:
Any ideas?
Kaspar
On 16.08.2009, at 12:43, Kaspar Fischer wrote:
Dear list,
After some hours of research I realise that I need some advice on
how to tackle this: My goal is to render a graph [1] consisting of
at most 100 nodes and 300 edges (most of the time the graph will be
much smaller, though). I have an algorithm to position the nodes
and the algorithm works in iterations so that I can use
intermediate positions to animate the placement of the nodes.
Ultimately, I want a scrolling view that allows the user to view
the graph and pinch-zoom or double-tap zoom into it. When zooming
in and when the user scrolls, it's okay if the parts that become
visible are initially blurry and will get redrawn a little later. I
need to be able to catch touch events on the nodes.
I have played around with a UIScrollView and an associated
UIViewController<UIScrollViewDelegate>; the scroll view contains a
custom view that draws the complete graph in its -(void)drawRect:
(CGRect)rect method. I have two problems with this approach: On the
one hand, when the user zoomed in, even though drawRect: is called
again, it draws a blurry graph [2]. On the other hand, I am not
sure how to animate the graph with this approach: I have no layers
so I basically have to do the animation myself and I fear this does
not leverage any of the iPhone's hardware capabilities (layer
composition, etc).
I plan to have a background thread that runs the algorithm and at
the end of each iteration tells the main (UI) thread the new
positions of the nodes.
The questions I have:
1. Would you implement each graph node as a CALayer so that it can
easily be animated, or will that result in too many layers for the
iPhone's Core Animation framework?
2. Should I use UIScrollView? It already provides the scrollbars,
the zooming and panning but I could not remove the blurriness/
unsharpness.
I have also come across CATiledLayer but I am not sure whether they
were intended to have sublayers (representing the nodes and edges).
Thanks in advance for any advice on any of these questions!
Kaspar
--
[1] a drawing as you can see on http://en.wikipedia.org/wiki/Graph_(mathematics)
[2] http://halmueller.wordpress.com/2008/10/08/a-very-simple-uiscrollview-demo/
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