使用绑定中断 RecyclerView 项目布局

Question

我正在使用 Kotlin 构建一个 Android 应用程序，并决定替换对 findViewById 的调用并使用绑定。这一切都很好，但特别是，当我为 RecyclerView 更改适配器时，它会破坏项目布局。

带有findViewById的原始代码：

class WeightListAdapter(val weights: List<WeightWithPictures>, val onWeightItemClickListener: OnWeightItemClickListener) : RecyclerView.Adapter<WeightListAdapter.WeightHolder>()  {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WeightListAdapter.WeightHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.list_item_weight, parent, false)
        return WeightHolder(view)
    }

    override fun onBindViewHolder(holder: WeightListAdapter.WeightHolder, position: Int) {
        val weightWithPictures = weights[position]
        holder.bind(weightWithPictures)
    }

    override fun getItemCount() = weights.size

    inner class WeightHolder(itemView: View) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
        private lateinit var weight: Weight
        private val weightValueView: TextView = this.itemView.findViewById(R.id.weightValue)
        private val weightDateView: TextView = this.itemView.findViewById(R.id.weightDate)
        private val weightImageView: ImageView = this.itemView.findViewById(R.id.weightImage) as ImageView

这是布局：

但是每当我使用绑定时：

class WeightListAdapter(val weights: List<WeightWithPictures>, val onWeightItemClickListener: OnWeightItemClickListener) : RecyclerView.Adapter<WeightListAdapter.WeightHolder>()  {

    private var _binding: ListItemWeightBinding? = null
    private val binding get() = _binding!!

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WeightListAdapter.WeightHolder {
        _binding = ListItemWeightBinding.inflate(LayoutInflater.from(parent.context))
        val view = binding.root
        return WeightHolder(view)
    }

    override fun onBindViewHolder(holder: WeightListAdapter.WeightHolder, position: Int) {
        val weightWithPictures = weights[position]
        holder.bind(weightWithPictures)
    }

    override fun getItemCount() = weights.size

    inner class WeightHolder(itemView: View) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
        private lateinit var weight: Weight
        private val weightValueView: TextView = binding.weightValue
        private val weightDateView: TextView = binding.weightDate
        private val weightImageView: ImageView = binding.weightImage

布局中断：

关于我在这里做错了什么有什么想法吗？是bug吗？

P.S - 现在，我只是为项目视图添加注释以忽略绑定为 documented here，但我真的很想了解问题所在。

Answer 1

您的绑定需要在其父级的上下文中进行扩展，以便其根视图的布局参数生效：

binding = ListItemWeightBinding.inflate(LayoutInflater.from(parent.context), parent, false)

如果您尝试长期使用它，我认为您正在为适配器创建binding 属性也会给您带来问题。每个 ViewHolder 都拥有一个具有不同绑定实例的不同视图。它现在可以工作了，因为您只在设置每个实例后立即将它用于 ViewHolder 实例化。但如果这就是你的全部意图，你应该只将绑定传递给 ViewHolder 的构造函数并省略适配器的属性。

顺便说一下，这是我用于 ViewHolders 的那种模式。更少的代码。请注意，它不必是 inner 类。

class WeightHolder(binding: ListItemWeightBinding) : RecyclerView.ViewHolder(binding.root), View.OnClickListener {

    fun bind(item: WeightWithPictures) {
        with (binding) {
            // set data for views here
        }
    }
}

Answer 2

我同意@Tenfour04，使用相同的绑定实例是错误的，但我相信您的问题的根本原因在于绑定逻辑。通过绑定，数据将绑定到视图，但不会立即。所以你的视图被夸大了，但由于绑定发生在稍后阶段，计划在不久的将来发生，item_view 的宽度被缩小了。

所以试试下面的，

// oncreate view logic 
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WeightListAdapter.WeightHolder {
        val binding = ListItemWeightBinding.inflate(LayoutInflater.from(parent.context), parent, false)
        return WeightHolder(binding)
    }

// onBindViewHolder logic remains the same

// this remains same as suggested by @Tenfour04 but a change in the bind function
 
class WeightHolder(binding: ListItemWeightBinding) : RecyclerView.ViewHolder(binding.root), View.OnClickListener {

    fun bind(item: WeightWithPictures) {
        with (binding) {
            // set data for views using databindig
            customVariable = item           
            executePendingBindings() // this is important
        }
    }
}

// define the customvariable in your `item_list_view.xml`
        <variable
            name="customVariable"
            type="packagename.WeightWithPictures" />

executePendingBindings() 是我们强制绑定立即发生而不是稍后安排的方式

编辑：

这个答案来自Databinding，而不是ViewBinding