UILabel顶部对齐

在显示文字时，首先计算显示当前的文字需要多宽和多高，然后将对应的UILabel的大小改变成对应的宽度和高度.

该方法的代码如下:

UILabel *introduceLabel= [[UILabel alloc]init];

    CGSize maximumSize = CGSizeMake(screenBounds.size.width-20, 9999);

    NSString *dateString = self.businessInfo[0].vendorsIntroduction;

    UIFont *dateFont = [UIFont fontWithName:@"Helvetica" size:14];

    CGSize dateStringSize = [dateString sizeWithFont:dateFont 

                                   constrainedToSize:maximumSize 

                                       lineBreakMode:introduceLabel.lineBreakMode];

    CGRect dateFrame = CGRectMake(10.0f, 110.0f, screenBounds.size.width-20, dateStringSize.height);

    

    introduceLabel.text = self.businessInfo[0].vendorsIntroduction;

    introduceLabel.font = dateFont;

    introduceLabel.backgroundColor = [UIColor clearColor];

    introduceLabel.lineBreakMode = UILineBreakModeWordWrap;

    introduceLabel.numberOfLines = 0;

    introduceLabel.frame = dateFrame;

    [myscrollview addSubview:introduceLabel];

    [introduceLabel release];