設置多行文字，每行文字大小，顏色不一樣，這個是比較常見的
1.導入YYKit框架
2.寫代碼
NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
style.lineSpacing = 3;//行距
//第一行的屬性字符串
NSMutableAttributedString *attri = [[NSMutableAttributedString alloc] initWithString: @"立即支付" attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:14.f],NSForegroundColorAttributeName:RGB(102, 102, 102),NSParagraphStyleAttributeName:style}];
//第二行的屬性字符串
NSMutableAttributedString *attri2 = [[NSMutableAttributedString alloc] initWithString: @"\n(第二行)" attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:8.f],NSForegroundColorAttributeName:RGB(102, 102, 102),NSParagraphStyleAttributeName:style}];
[attri appendAttributedString:attri2];
self.payBtn.titleLabel.attributedText = attri;
self.payBtn.titleLabel.numberOfLines=0;
self.payBtn.titleLabel.textAlignment =NSTextAlignmentCenter;
