UILabel set to center of view

Question

How come the UILabel drawn in this code is not in the center of the view?

//create the view and make it gray
UIView *view = [[UIView alloc] init];
view.backgroundColor = [UIColor darkGrayColor];

//everything for label
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0,0,42,21)];

//set text of label
NSString *welcomeMessage = [@"Welcome, " stringByAppendingString:@"username"];
welcomeMessage = [welcomeMessage stringByAppendingString:@"!"];
label.text = welcomeMessage;

//set color
label.backgroundColor = [UIColor darkGrayColor];
label.textColor = [UIColor whiteColor];

//properties
label.textAlignment = NSTextAlignmentCenter;
[label sizeToFit];

//add the components to the view
[view addSubview: label];
label.center = view.center;

//show the view
self.view = view;

The line, label.center = view.center; should move the label to the center of the view. But instead moves it to where the center of the label is in the left hand corner of the view as shown below.

_{(source: gyazo.com)}

Does anyone know why?

Solution 1

You need to init your view with a frame:

UIView *view = [[UIView alloc] initWithFrame:self.view.frame];

Solution 2

This is caused by your view variable not having a frame defined. By default it has a frame set to (0, 0, 0, 0), so its center is (0, 0).

Hence when you do label.center = view.center;, you set the center of your label to (0 - label.width / 2, 0 - label.height /2). (-80.5 -10.5; 161 21) in your case.

There is no need for a new UIView if your UIViewController already have one, just work with self.view.

- (void)viewDidLoad
{
    [super viewDidLoad];

    //create the view and make it gray
    self.view.backgroundColor = [UIColor darkGrayColor];

    //everything for label
    UILabel *label = [[UILabel alloc] init];

    //set text of label
    // stringWithFormat is useful in this case ;)
    NSString *welcomeMessage = [NSString stringWithFormat:@"Welcome, %@!", @"username"];
    label.text = welcomeMessage;

    //set color
    label.backgroundColor = [UIColor darkGrayColor];
    label.textColor = [UIColor whiteColor];

    //properties
    label.textAlignment = NSTextAlignmentCenter;
    [label sizeToFit];

    //add the components to the view
    [self.view addSubview: label];
    label.center = self.view.center;
}

Also note that doing label.center = self.view.center will not work properly when rotating to landscape mode.