CATiledLayer drawing delay

I am developing an iphone app. It has following page structure, 1.List of game levels in a UITableView 2.Game page

I use "UIViewAnimationTransitionFlipFromRight" between pages

Game page has 3 views, One is a scrollView in that my game grid is drawn. Game grid is a sub class of UIView ,that added to Scrollview. To support zooming i use CATiledLayer to draw the grid(20*20).

MY problem is GameGrid shows white or last played puzzles grid contents for a few seconds and then refresh(flashing) to the new content.

My GameGrid class as follows

`

 @implementation GameGrid

+(Class)layerClass
{    
 return [CATiledLayer class];
}

 - (id)initWithFrame:(CGRect)frame {   
        if ((self = [super initWithFrame:frame])) {
           CATiledLayer *tempTiledLayer = (CATiledLayer*)self.layer;
           tempTiledLayer.levelsOfDetail = 5;
           tempTiledLayer.levelsOfDetailBias = 2;        
              self.opaque=YES;  
           }
             return self;
}

-(void)drawRect:(CGRect)r
{
 //empty
}

-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context
{
 // here i am drawing grid
// filling rect
 // lines
// string etc..
}