設定 NavigationItem 的 title 字體、大小、位置

設定字體大小：
Label.font = [UIFont systemFontOfSize:50];

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設定字體與大小：
Label.font = [UIFont fontWithName:@"Helvetica" size:50];

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設定 NavigationItem 的 title 字體、大小、位置
UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 320/2, 44)];titleLabel.textAlignment = NSTextAlignmentCenter;titleLabel.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);titleLabel.font = [UIFont fontWithName:@"Helvetica" size:23];titleLabel.text = @“Title”;
UINavigationItem *naviItem = [[UINavigationItem alloc] init];naviItem.titleView = titleLabel;