ios7以上自定义导航栏标题的字体大小及颜色的方法

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0,0,0,0)];//这个frame是初设的，没关系，后面还会重新设置其size。
    [label setNumberOfLines:0];
    UIFont *font = [UIFont fontWithName:@"Arial" size:17];
    label.font = font;
    label.text = @"二维码结果";
    CGSize size = CGSizeMake(320,2000); //设置一个行高上限
    NSDictionary *attribute = @{NSFontAttributeName: label.font};
    CGSize labelsize = [label.text boundingRectWithSize:size options: NSStringDrawingTruncatesLastVisibleLine|NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:attribute context:nil].size;  //动态根据文本内容设置lable的大小
    [label setFrame:CGRectMake(0,0, labelsize.width, labelsize.height)];
    self.navigationItem.titleView = label;

NSArray* fontFamilys = [UIFont familyNames];
    for (int i = 0; i<[fontFamilys count]; i++) {
        NSString* family = [fontFamilys objectAtIndex:i];
        NSLog(@"系统自带字体有:%@rn=====",family);
        NSArray* fonts = [UIFont fontNamesForFamilyName:family];
        for (int j = 0; j<[fonts count]; j++) {
            NSLog(@"%@",[fonts objectAtIndex:j]);
        }
    }