Stop drawing of CATiledLayer - objective-c

Question

Is is possible to stop CATiledLayer to draw (drawLayer:inContext)?
It draws asynchronously and when i try to release CGPDFDocumentRef, which is used by CATiledLayer, the app crashes (EXC_BAD_ACCESS).
That's my view:
#implementation TiledPDFView
- (id)initWithFrame:(CGRect)frame andScale:(CGFloat)scale{
if ((self = [super initWithFrame:frame])) {
CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];
tiledLayer.levelsOfDetail = 4;
tiledLayer.levelsOfDetailBias = 4;
tiledLayer.tileSize = CGSizeMake(512.0, 512.0);
myScale = scale;
}
return self;
}
// Set the layer's class to be CATiledLayer.
+ (Class)layerClass {
return [CATiledLayer class];
}
- (void)stopDrawing{
CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];
[tiledLayer removeFromSuperlayer];
tiledLayer.delegate = nil;
}
// Set the CGPDFPageRef for the view.
- (void)setPage:(CGPDFPageRef)newPage
{
CGPDFPageRelease(self->pdfPage);
self->pdfPage = CGPDFPageRetain(newPage);
//self->pdfPage = newPage;
}
-(void)drawRect:(CGRect)r
{
}
// Draw the CGPDFPageRef into the layer at the correct scale.
-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context
{
// First fill the background with white.
CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
CGContextFillRect(context,self.bounds);
CGContextSaveGState(context);
// Flip the context so that the PDF page is rendered
// right side up.
CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Scale the context so that the PDF page is rendered
// at the correct size for the zoom level.
CGContextScaleCTM(context, myScale,myScale);
CGContextDrawPDFPage(context, pdfPage);
CGContextRestoreGState(context);
}
// Clean up.
- (void)dealloc {
CGPDFPageRelease(pdfPage);
[super dealloc];
}
And this is where i try to stop and release PDF in view controller:
v is instance of TiledPDFView
-(void) stopDwaring {
[v stopDrawing];
[v removeFromSuperview];
[v release];
[self.view removeFromSuperview];
self.view = nil;
CGPDFDocumentRelease(pdf);
}

Answer 1

this post helped me solving my own trouble with CATiledLayer. I used TiledPDFview.m from Apple's documentation as example.
Since I need to redraw the entire view and all tiles at some point, I use a CATiledLayer as property.
When exiting and deallocating the viewcontroller, it crashed with [CATiledLayer retain]: Message sent to deallocated instance.
Here is my dealloc method of the view controller:
- (void)dealloc {
self.tiledLayer.contents=nil;
self.tiledLayer.delegate=nil;
[self.tiledLayer removeFromSuperlayer];
// note: releasing the layer still crashes-
// I guess removeFromSuperlayer releases it already,
// but couldn't find documentation so far.
// So that's why it's commented out:
// [self.tiledLayer release], self.tiledLayer=nil;
//release the other viewcontroller stuff...
[super dealloc];
}
That works for me. Hope it helps someone.

Answer 2

Remove the CATiledLayer from its superlayer before releasing the CGPDFDocumentRef.
[yourTiledLayer removeFromSuperlayer];
Dont forget to set it's delegate to nil too.
yourTiledLayer.delegate = nil;
After that, you can safely release your CGPDFDocumentRef.
Edit after OP adds code:
Did you get pdfPage using CGPDFDocumentGetPage()? If so, you shouldn't release it, it is an autoreleased object.
Regarding how to add it as sublayer:
You don't actually need TiledPDFView. In your view controller, you can simply do this:
CATiledLayer *tiledLayer = [CATiledLayer layer];
tiledLayer.delegate = self; //sets where tiledLayer will look for drawLayer:inContext:
tiledLayer.tileSize = CGSizeMake(512.0f, 512.0f);
tiledLayer.levelsOfDetail = 4;
tiledLayer.levelsOfDetailBias = 4;
tiledLayer.frame = CGRectIntegral(CGRectMake(0.0f, 0.0f, 512.0f, 512.0f));
[self.view.layer addSublayer:tiledLayer];
Then move your drawLayer:inContext: implementation to your view controller.
Then in your view controller's dealloc, release it as:
[tiledLayer removeFromSuperlayer];
tiledLayer.delegate = nil;
CGPDFDocumentRelease(pdf);
Note that you can't do this on a UIView subclass, as the drawLayer:inContext: will conflict with the UIView's main layer.

Answer 3

object.layer.contents = Nil
This should wait for the thread to finish. It helped in my case.

Answer 4

TiledPDFView *pdfView;
In dealloc of pdfView's superview class, write below line of codes.
- (void)dealloc {
if (nil != self.pdfView.superview) {
self.pdfView.layer.delegate = nil;
[self.pdfView removeFromSuperview];
}
}
This works for me. Hope it will help.

Answer 5

I've had a similar problem.
I ended up setting a float variable "zoom" in my TiledPDFView which I set as the zoomScale of PDFScrollView in the UIScrollview Delegate method: scrollViewDidZoom
Then in my drawLayer method inside TiledPDFView I only called the contents of that method if the float variable "zoom" was above 2.
This fixes any issues of someone leaving the view without zooming. It may not be ideal for your case as this error still occurs if someone zooms above 2 then releases the viewcontroller quickly, but you might be able to find a similar technique to cover all bases.

Answer 6

It looks like you're doing the same thing I am, which is borrowing the ZoomingPDFView code and integrating it into your project. If your UIScrollView delegate methods in PDFScrollView are unchanged, you can solve your problem by just commenting both lines of your dealloc method (in TiledPDFView). That stuff should only be happening when you kill the parent view, anyway.