Question

I wrote the code below to make move an image from the top to the button by using NSTimer. However when I run it I cannot have the images separately. Basically, the image leaves trace. what I want is to have the image frame by frame it is moving. What am I missing?

-(void)printOut:(NSTimer*)timer1;
{

    image = [[UIImageView alloc] initWithFrame:CGRectMake(50, -50+m, 50, 50)];
    [image setImage:[UIImage imageNamed:[NSString stringWithFormat:@"image.png"]]];

    CGRect oldFrame = image.frame;
    image.frame = CGRectMake(oldFrame.origin.x+5, oldFrame.origin.y, oldFrame.size.width, oldFrame.size.height);

    [self.view addSubview:image];

    m++;
    if (m == 1000) {
        [timer1 invalidate];
    }

}

edit: I don’t want to use animation. Because later on I need to use collision detection and it is not possible to control the coordinates of the animations.

Answer 1

You are allocating and adding subView every time to the self. When are you removing the ImageView to disappear the Previous ImageView. So try removing the image before allocating. Try like this

-(void)printOut:(NSTimer*)timer1;
{
[image removeFromSuperview];
image = nil;
image = [[UIImageView alloc] initWithFrame:CGRectMake(50, -50+m, 50, 50)];
[image setImage:[UIImage imageNamed:[NSString stringWithFormat:@"image.png"]]];

CGRect oldFrame = image.frame;
image.frame = CGRectMake(oldFrame.origin.x+5, oldFrame.origin.y, oldFrame.size.width, oldFrame.size.height);

[self.view addSubview:image];

m++;
if (m == 1000) {
    [timer1 invalidate];
}
}