一、DZNEmptyDataSet使用

// 偏移量 - 向上偏移64像素
func verticalOffset(forEmptyDataSet scrollView: UIScrollView) -> CGFloat {
    return -64.0
}

// 显示图片
func image(forEmptyDataSet scrollView: UIScrollView) -> UIImage? {
    return UIImage(named: "blank")
}

// 允许刷新
func emptyDataSetShouldAllowScroll(_ scrollView: UIScrollView) -> Bool {
    return true
}

// 文字显示
func title(forEmptyDataSet scrollView: UIScrollView) -> NSAttributedString? {
    let title = "暂时没有数据"
    let attributes = [NSFontAttributeName: UIFont.boldSystemFont(ofSize: 15),
                      NSForegroundColorAttributeName: UIColor(hexColor: "c5c5c5")]
    return NSAttributedString(string: title, attributes: attributes)
}
    
// 点击重试
func buttonTitle(forEmptyDataSet scrollView: UIScrollView, for state: UIControlState) -> NSAttributedString? {
    let title = "暂时没有数据，请点击重试哦~"
    let font = UIFont.systemFont(ofSize: 15)
    let attString = NSMutableAttributedString(string: title)
    attString.addAttribute(NSFontAttributeName, value: font, range: NSMakeRange(0, title.characters.count))
    attString.addAttribute(NSForegroundColorAttributeName, value: UIColor(hexColor: "c5c5c5"), range: NSMakeRange(0, title.characters.count))
    attString.addAttribute(NSForegroundColorAttributeName, value: UIColor(hexColor: "0093fa"), range: NSMakeRange(8, 4))
    return attString
}

// 自定义视图
func customView(forEmptyDataSet scrollView: UIScrollView) -> UIView? {
    // 当数据还没有加载完成的时候，显示空
    return isLoadDataFinish ? PlaceHolderView() : nil
}