CGSize constraintSize;
constraintSize.width = 320;
constraintSize.height = MAXFLOAT;
CGSize sizeFrame =[infoTextView.text sizeWithFont:infoTextView.font = [UIFont systemFontOfSize:12.0] constrainedToSize:constraintSize lineBreakMode:NSLineBreakByWordWrapping];
infoTextView.frame = CGRectMake(10,titleLabel.frame.origin.y+titleLabel.frame.size.height,sizeFrame.width,sizeFrame.height+5);
注：这个方法在 textFiledView中不是非常精确