iOS-tableHeaderView利用自动布局自适应高度

效果：

关键点0：

headerView的子View的布局一定要从headerView的最上面开始填充，然后依次往下面设置布局

private func setupSubViews(){
        topView = UIView()
        topView.backgroundColor = YZJRandomColor()
        addSubview(topView)
        topView.snp.makeConstraints { (make) in
            make.left.right.top.equalTo(self)
            make.height.equalTo(99)
        }
        
        middleView = UIView()
        middleView.backgroundColor = YZJRandomColor()
        addSubview(middleView)
        middleView.snp.makeConstraints { (make) in
            make.top.equalTo(topView.snp.bottom)
            make.left.right.equalTo(self)
            make.height.equalTo(103)
        }
        
        bottomView = UIView()
        bottomView.backgroundColor = YZJRandomColor()
        addSubview(bottomView)
        bottomView.snp.makeConstraints { (make) in
            make.top.equalTo(middleView.snp.bottom)
            make.left.right.equalTo(self)
            make.height.equalTo(129)
        }
}

关键点1：

第一次显示的时候，需要在headerView类的didMoveToSuperview里面设置布局（宽度的布局一定要设置）

override func didMoveToSuperview() {
        super.didMoveToSuperview()
        if superview != nil{
            snp.remakeConstraints { (make) in
                make.width.equalTo(superview!)
                make.bottom.equalTo(bottomView)
            }
            layoutIfNeeded()
        }
}

关键点2：

headerView布局修改后需要调用superview?.layoutIfNeeded()，并重新赋值tableView的tableHeaderView

        topView.snp.remakeConstraints { (make) in
            make.left.right.top.equalTo(self)
            make.height.equalTo(randomHeight())
        }
        middleView.snp.remakeConstraints { (make) in
            make.top.equalTo(topView.snp.bottom)
            make.left.right.equalTo(self)
            make.height.equalTo(randomHeight())
        }
        
        bottomView.snp.remakeConstraints { (make) in
            make.top.equalTo(middleView.snp.bottom)
            make.left.right.equalTo(self)
            make.height.equalTo(randomHeight())
        }
        superview?.layoutIfNeeded()

        headerView.change()
        tableView.tableHeaderView = headerView

关键点3（iOS9会有影响）：

• 使用自动布局的时候先设置tableView的布局再给tableView.tableHeaderView赋值

        tableView.snp.makeConstraints { (make) in
            make.edges.equalTo(view)
        }
        tableView.tableHeaderView = headView

• headerView里面只能有一个外包的容器View，不能容器View再套容器View进行自适应（外部的容器View布局依赖于里面容器View的布局）

demo地址