Question

Apple docs have this to say:

UIBarButtonSystemItemFlexibleSpace
Blank space to add between other items. The space is distributed equally between the other items. Other item properties are ignored when this value is set.

That’s a little vague (exactly what space is distributed equally?) So I wrote a test method:

-(void) createToolbar {
    BOOL stuffInTopLeftCorner = NO;
    UIToolbar* bar = [[UIToolbar alloc]initWithFrame:CGRectMake(0, 0, 1024, 44)];
    self.bar = bar;
    [self addSubview:bar];
    UILabel* titleLabel = [[UILabel alloc]initWithFrame:CGRectZero];
    titleLabel.text = @"Centered title";
    titleLabel.font = [UIFont systemFontOfSize:30];
    [titleLabel sizeToFit];
    CGSize titleSize = [titleLabel bounds].size;
    NSLog(@"titleSize is %g %g", titleSize.width, titleSize.height);
    UIBarButtonItem* titleItem = [[UIBarButtonItem alloc]initWithCustomView:titleLabel];
    UIBarButtonItem* flexibleSpace = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
    UILabel* leftLabel = [[UILabel alloc]initWithFrame:CGRectZero];
    leftLabel.text = @"Stuff in top left corner";
    leftLabel.font = [UIFont systemFontOfSize:30];
    [leftLabel sizeToFit];
    UIBarButtonItem* topLeftCornerItem = [[UIBarButtonItem alloc]initWithCustomView:leftLabel];
    NSMutableArray* items = [NSMutableArray arrayWithObjects: flexibleSpace, titleItem, flexibleSpace, nil];
    if (stuffInTopLeftCorner) {
        [items insertObject:topLeftCornerItem atIndex:0];
    }
    bar.items = items;
}

Here is what it looks like with the code as above:

And here is what it looks like if I change stuffInTopLeftCorner to YES:

It appears that adding something to the left of the title did not cause said title to move at all.

My question is — does that mean it will always center the title, regardless of what goes on either side of it?

Answer 1

As best I can tell, yes, it always centers the title, assuming that is possible.