thanks Matt, I did see your message and I did try layoutSublayersOfLayer: (I
assume that works because the UIView is automatically the CALayer's delegate)
and I still have the problem. However I agree your simple example is the
equivalent of what I'm doing, and I just compiled a version of it, and it works
and it doesn't flash. QED, despite having torn my code apart numerous times, I
must still be missing something.
Thanks for the example showing that it should work, I will now return to my
code and hunt harder to find what I've messed up here.
On 03-Feb-2011, at 4:32 AM, Matt Neuburg wrote:
> I really think you ought to try what I said. I just did and I'm not seeing
> any flash. Here's my code:
>
>
> - (IBAction) doButton: (id) sender { // toggle view size
> CGRect f = self->mmview.frame;
> if (f.size.height == 200) {
> f.size.height = f.size.width = 100;
> self->mmview.frame = f;
> return;
> }
> if (f.size.height == 100) {
> f.size.height = f.size.width = 200;
> self->mmview.frame = f;
> return;
> }
> }
>
> And here's the code for the view subclass:
>
> - (void) awakeFromNib {
> [super awakeFromNib];
> CALayer* lay = [CALayer layer];
> lay.frame = self.layer.bounds;
> [self.layer addSublayer: lay];
> lay.contents = (id)[[UIImage imageNamed:@"manny.jpg"] CGImage];
> self.which = @"manny";
> }
>
> - (void) layoutSublayersOfLayer: (CALayer*) layer {
> [CATransaction setDisableActions:YES]; // looks fine without this, too
> for (CALayer* lay in layer.sublayers) {
> lay.frame = layer.bounds;
> if (lay.contents) {
> if ([self.which isEqualToString:@"manny"]) {
> lay.contents = (id)[[UIImage imageNamed:@"moe.jpg"] CGImage];
> self.which = @"moe";
> }
> else if ([self.which isEqualToString:@"moe"]) {
> lay.contents = (id)[[UIImage imageNamed:@"manny.jpg"] CGImage];
> self.which = @"manny";
> }
> }
> }
> }
>
> So it seems to me I'm doing exactly what you said; when the view changes
> frame, I'm changing the sublayer frame to match, plus I'm changing the
> sublayer contents. And there's no flash.
>
> m.
>
> On Wed, 2 Feb 2011 18:29:48 +0800, Roland King <r...@rols.org> said:
>>
>> On 02-Feb-2011, at 1:38 AM, David Duncan wrote:
>>
>>> On Feb 1, 2011, at 4:32 AM, Roland King wrote:
>>>
>>>> I have a UIView subclass in my iOS app and the content for that UIView is
>>>> 3 CALayers, each with a bitmap image for their content, added as sublayers
>>>> of the UIView's layer. Each of the CALayers is the full size of the
>>>> UIView's layer (they have transparency to composite them together).
>>>>
>>>> When the UIView is resized the setFrame: method is called and I have a
>>>> custom implementation of that which sets the bounds of the sublayers so
>>>> they again fill the UIView's layer, and draws a new bitmap for each of
>>>> them of the right size and sets it into their contents.
>>>>
>>>> However, when I resize, there's a brief flash of the current content,
>>>> before it's been redrawn, stretched to fill the new sized window, before
>>>> the new content replaces it. Nothing I've tried has been able to stop that
>>>> brief flash and I can't figure out where it's coming from.
>>>
>>>
>>> I suppose my first question is why not just use UIViews instead? They
>>> should already abstract all of what you need to make this work away from
>>> you, and you should only need to set the view's contentMode property to
>>> UIViewContentModeRedraw to get the behavior you seem to desire. Then it
>>> would just be a matter of teaching the UIViews how to draw themselves to
>>> generate their own content instead of having the parent UIView do so and
>>> push it to them.
>>>
>>> As for overall, I'm not entirely certain what is happening, but it sounds
>>> like you have a timing issue, possibly one where the view's are resized on
>>> one runloop invocation and their contents replaced on the next. Instead of
>>> overriding -setFrame: you should override -layoutSubViews: which should
>>> catch more cases where layout is needed and allow you to do the work you
>>> need at the right time.
>>> --
>>> David Duncan
>>>
>>
>> Yeah I ended up with layers because I started constructing one UIImage by
>> drawing to a bitmap context and then split it up into three pieces
>> (backdrop, bit in the middle and an overlay) so I didn't have to keep
>> redrawing the bits that weren't changing and at that point I though layers
>> instead of images, but I certainly try to pull myself up the tree a bit and
>> move it back to UIViews. I'm just bothered that I can't figure this out,
>> CALayers should work ok for this.
>>
>> -layoutSubViews: doesn't work for this either, I tried that already, and
>> that does seem to ensure I end up with the calls on two different runloop
>> invocations, which is worse.
>>
>> I tend to agree that it's a timing issue, but I can't find it, I'm
>> explicitly doing everything in the one method, removing layers or removing
>> their contents before they are resized etc, so the only thought I'm left
>> with is that core animation is shifting the actual work to another thread,
>> even when I've turned off actions and put things in CATransactions and
>> whatever order I do things in makes little difference, that thread sees the
>> net change and animates between it, doing the resize first.
>>
>> Thanks for the reply though, if I can't sort this out (and I have perhaps
>> one more good idea) I'll try using UIImageViews instead.
>>
>>
>>
>>
>
> --
> matt neuburg, phd = m...@tidbits.com, <http://www.apeth.net/matt/>
> A fool + a tool + an autorelease pool = cool!
> AppleScript: the Definitive Guide - Second Edition!
> http://www.apeth.net/matt/default.html#applescriptthings
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