Question

i m pulling an image from an url and showing it in an imageview.what i want is an fadein animation effect when the image gets loaded from the url.i m using a background threading below is the code..

    NSOperationQueue *theQueue=[[[NSOperationQueue alloc]init]autorelease];

    NSInvocationOperation *theOp=[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(loadImage) object:nil]; 

    [theQueue addOperation:theOp];  
}

-(void)loadImage
{

    NSAutoreleasePool *pool=[[NSAutoreleasePool alloc]init];
    [activityIndicator startAnimating];
    NSString *imagefile = [image  objectAtIndex:0]; 
    NSURL *url1=[NSURL URLWithString:imagefile];
    NSData *data = [NSData dataWithContentsOfURL:url1];
    UIImage *ui=[[UIImage alloc]initWithData:data];
    NSLog(@"awesome:%@",ui);
    [ui beginAnimations:@"" context:nil];
    bigbanner.image=ui;
    [activityIndicator stopAnimating];
    [pool release];
}

Answer 1

Yes what you say is absolutely correct and thats the way to do it. I wrote this method & always use this to Fade in my image. I deal with CALayer for this. You need to import Quartz framework for this.

#import <QuartzCore/QuartzCore.h>

...

- (void)fadeInLayer:(CALayer *)l
{
    CABasicAnimation *fadeInAnimate   = [CABasicAnimation animationWithKeyPath:@"opacity"];
    fadeInAnimate.duration            = 0.5;
    fadeInAnimate.repeatCount         = 1;
    fadeInAnimate.autoreverses        = NO;
    fadeInAnimate.fromValue           = [NSNumber numberWithFloat:0.0];
    fadeInAnimate.toValue             = [NSNumber numberWithFloat:1.0];
    fadeInAnimate.removedOnCompletion = YES;
    [l addAnimation:fadeInAnimate forKey:@"animateOpacity"];
    return;
}

Usage: If you are using this from your current file, then –

    [self fadeInLayer:imageView.layer];

Hope this helps