Trouble with CGRectMake

I have been trying to create a grid on the iPhone of 16x16 images.

- (void)viewDidLoad {
    [super viewDidLoad];

    int xLocation = 0;

    for (int i=0; i <= 619; i++) {


        if (((i % 30) == 0) && i != 0) { //if at end of column (30th row), moves x over 16 px to next column
            xLocation += 16;
        }
        else {;}


    CGRect imageRect 开发者_JAVA技巧= CGRectMake( xLocation, (16*i), 16, 16);
    UIImageView *image = [[UIImageView alloc] initWithFrame:imageRect];
    [image setImage:[UIImage imageNamed:@"Untitled-1.png"]];
    [image setOpaque:YES];

        NSLog(@"%d", xLocation);


    [self.view addSubview:image];
    [image release];
    }

The problem is the int xLocation. For some reason, CGRectMake uses 0 in the x-coordinate slot instead of xLocation. I say "instead of" because the NSLog below it reveals that the xLocation has the values that I want it to, so the assignment of the values is working fine. What is going on here?

Casting xLocation as an int in your NSLog will certainly work, but you could also use:

NSLog(@"imageRect %@", NSStringFromCGRect(imageRect));

There are a whole series of NSStringFromXXX helper functions that come in handy from time to time.

The xLocation is 0 for the first column and it is being increased for each column but the y coordinate is not being reset to 0 for each new column. It just keeps increasing based on i. So the columns from the second onward are just off screen at the right xLocation but a high y value.

Try changing the imageRect calculation to:

CGRect imageRect = CGRectMake( xLocation, (16*(i % 30)), 16, 16);

%d doesn't present float's properly. Use %f or convert xLocation to an int:

NSLog(@"%d", (int)xLocation);

You can also simplify your xLocation calculation readability by calculating it each time, something like

16 * (i / 30)

The overhead is minimal on modern processors.