android - 使用数据绑定(bind)在 PagerAdapter 中回收 View

Question

我一直在尝试在我的 PagerAdapter 中实现回收，多亏了 this question，我可以成功地做到这一点但是我遇到了一个问题，无法通过数据绑定(bind)来缓存 View 。

我试过这样，保持 Stack<View> :

class CustomAdapter : PagerAdapter() {
    private var recycledViews: Stack<View> = Stack()

    var items: List<Item> = ArrayList()
        set(value) {
            field = value
            notifyDataSetChanged()
        }

    override fun instantiateItem(container: ViewGroup, position: Int): Any {
        val binding = inflateOrRecycle(container)

        binding.item = items[position]
        binding.handler = this

        container.addView(binding.root)
        return binding.root
    }

    private fun inflateOrRecycle(container: ViewGroup): CustomBinding {
        val inflater = LayoutInflater.from(container.context)

        return if (recycledViews.isEmpty()) {
            CustomBinding.inflate(inflater, container, false)
        } else {
            val view = recycledViews.pop()
            CustomBinding.bind(view)
        }
    }

    override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
        val view = `object` as View

        container.removeView(view)
        recycledViews.add(view)
    }
}

但是，每当它第一次尝试使用回收 View 并调用 CustomBinding.bind(view) 时它崩溃是因为 View 必须有一个标签。我搜索过这个，但我找到的答案都没有完全解决我的问题。

我也试过保留 Stack<CustomBinding> ，但问题是我不确定如何处理 destroyItem方法。因为如果我这样做:

override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
    val view = `object` as View

    container.removeView(view)
    recycledViews.add(CustomBinding.bind(view))
}

我仍然会遇到同样的错误。我怎样才能像这样“回收”数据绑定(bind)对象？或者，如果我回收 View 本身，我如何将它们转换回绑定(bind)对象？

Answer 1

我猜你犯了一个简单的错误。 如果我错了，您可以纠正我，我尝试使用这个适配器并且它有效。

val demoAdapter = object : PagerAdapter() {
        private var recycledViews: Stack<View> = Stack()

        var items: List<String> = ArrayList()
            set(value) {
                field = value
                notifyDataSetChanged()
            }

        override fun instantiateItem(container: ViewGroup, position: Int): Any {
            val binding = inflateOrRecycle(container)


            container.addView(binding.root)
            return binding.root
        }

        private fun inflateOrRecycle(container: ViewGroup): DemoItemBinding {
            val inflater = LayoutInflater.from(container.context)

            return if (recycledViews.isEmpty()) {
                DemoItemBinding.inflate(inflater, container, false)
            } else {
                val view = recycledViews.pop()
                val custBinding = DataBindingUtil.getBinding<DemoItemBinding>(view)
                if(custBinding == null)
                    DemoItemBinding.bind(view)
                else
                    custBinding
            }
        }

        override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
            val view = `object` as View

            container.removeView(view)
            recycledViews.add(view)
        }

        override fun isViewFromObject(view: View, `object`: Any): Boolean {
            return `object` is View && view.equals(`object`)
        }

        override fun getCount(): Int {
            return 4
        }
    }

我从你的代码中更改的部分是这个

return if (recycledViews.isEmpty()) {
            CustomBinding.inflate(inflater, container, false)
        } else {
            val view = recycledViews.pop()
            CustomBinding.bind(view)
        }

到

return if (recycledViews.isEmpty()) {
                DemoItemBinding.inflate(inflater, container, false)
            } else {
                val view = recycledViews.pop()
                val custBinding = DataBindingUtil.getBinding<DemoItemBinding>(view)
                if(custBinding == null)
                    DemoItemBinding.bind(view)
                else
                    custBinding
            }

我认为，您试图绑定(bind)到一个已经附加了 Binding 的 View 。因此它给了你一个错误。我所做的是检查任何以前的绑定(bind)，如果存在则返回关联的绑定(bind)。