placeHolderLabel.font = self.font;,设置多么大就是多大的,
if ( placeHolderLabel == nil )
{
placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
placeHolderLabel.lineBreakMode = UILineBreakModeWordWrap;
placeHolderLabel.numberOfLines = 0;
placeHolderLabel.font = self.font;
placeHolderLabel.backgroundColor = [UIColorclearColor];
placeHolderLabel.textColor = self.placeholderColor;
placeHolderLabel.alpha = 0;
placeHolderLabel.tag = 999;
[self addSubview:placeHolderLabel];
}