Question

Goal : I wants when I drag image it become fade so we can see background view.

How we increase or decrease the alpha value of image on dragging time?

thanks

Answer 1

I think you are asking for sample code. you can make a class subclass of UIImageView. Like:

.h

@interface YourImageController : UIImageView
{
    CGPoint startLocation;
}
@end

.m

@implementation YourImageController
- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {   
    [self setAlpha:x.x];

    // Retrieve the touch point
    CGPoint pt = [[touches anyObject] locationInView:self];
    startLocation = pt;
}

-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    [self setAlpha:x.x];
    CGPoint pt = [[touches anyObject] locationInView:self];
    CGFloat dx = pt.x - startLocation.x;
    CGFloat dy = pt.y - startLocation.y;

    CGPoint newCenter = CGPointMake(self.center.x + dx, self.center.y + dy);

    self.center = newCenter;
}
 -(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
 {
    [self setAlpha:1.0];
 }