UILable上的文字，根据frame的大小自动调整字体的大小，使字体最大（全部显示出来，字体是单行的，而不是自动换行）

UILabel * lbl1 = [[UILabel alloc] initWithFrame:CGRectMake(50, 50, 200, 100)];

    lbl1.text = @"高30，长100，设置自适应宽度";

//    lbl1.adjustsFontSizeToFitWidth = YES;

    lbl1.font = [UIFont systemFontOfSize:50.0];

    lbl1.textAlignment = NSTextAlignmentRight;

    [lbl1 setBackgroundColor:[UIColor lightGrayColor]];

    

    CGSize size = [lbl1 sizeThatFits:CGSizeMake(lbl1.frame.size.width, MAXFLOAT)];

    

    while (lbl1.frame.size.width < size.width) {

        lbl1.font = [UIFont systemFontOfSize:lbl1.font.pointSize-1];

        size = [lbl1 sizeThatFits:CGSizeMake(lbl1.frame.size.width, MAXFLOAT)];

    }