来自视图适配器的无条件布局膨胀。科特林

Question

我在 Android Studio 中收到以下警告： “来自视图适配器的无条件布局膨胀：应该使用 View Holder 模式（使用传递给此方法的回收视图作为第二个参数）以获得更平滑的滚动。”在 inflater.inflate(R.layout.animal_ticket, null) 行。

如何修复警告？我无法找到该问题的解决方案。

谢谢！

override fun getView(p0: Int, p1: View?, p2: ViewGroup?): View {
        val animal = listOfAnimals[p0]
        val inflater = LayoutInflater.from(context)
        var holder = ViewHolder()
        val myView = inflater.inflate(R.layout.animal_ticket, null)
        myView.tvName.text = animal.name!!
        myView.tvDes.text = animal.description!!
        myView.jvAnimalImage.setImageResource(animal.image!!)
        return myView
    }

Answer 1

如果之前有另一个相同视图类型的View（getItemViewType(position: Int) 返回相同的值）滚动到屏幕外，则列表视图可以在该实例中作为第二个参数传递给getView()。重用该视图比扩充一个新视图要快。

您还应该使用ViewHolder 来缓存有关视图的内容，例如相对昂贵的findViewById()。您可以通过标签将其附加到视图并从视图中检索它。

override fun getView(position: Int, convertView: View?, parent: ViewGroup?) {
    val animal = listOfAnimals[position]
    val myView = convertView ?:
        LayoutInflater.from(context).inflate(R.layout.animal_ticket, parent, false)
    val holder = myView.tag as? ViewHolder ?: ViewHolder(myView)
    myView.tag = holder
    holder.tvName.text = animal.name!! // etc
}

class ViewHolder(view: View) {
    val tvName: TextView = view.name // etc
}

Answer 2

对于任何 RecyclerView，您都需要自己的 ViewHolder 类，该类包含animal_ticket 中列出的所有视图。

基本上，它是这样工作的：

1) 创建 ViewHolder 以“保存”您要显示的项目的所有视图；

2) 将ViewHolder绑定到RecyclerView，并给里面的view赋值；

这是我写的一个示例适配器：

class MyActivity : Activity() {
//users is the list we're going to use to get information for the views
val users = ArrayList<User>()
//...getting user information
//.. your activity stuff here

//Creating our adapter
/* 
  Note that to extend the RecyclerView.Adapter, you need to specify a
  ViewHolder. The code becomes much easier to manage if you just put the 
  ViewHolder inside your adapter.
*/
inner class MyAdapter : RecyclerView.Adapter<MyAdapter.MyViewHolder>() {

    //This is the view holder
    inner class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        //Here you declare your views and get them from the itemView
        //The itemView is one that is passed each time to the RecyclerView
        //(the items inside your XML layout file)
        internal val userImageView = itemView.findViewById(R.id.userImage)
        internal val userFullName = itemView.findViewById(R.id.userName)
    }

    //This is where you return your own ViewHolder with your layout
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val layoutInflater = LayoutInflater.from(parent.context)
        //user_list_item.xml is below
        val itemView = layoutInflater.inflate(R.layout.user_list_item, parent, false))
        return MyViewHolder(itemView)
    }


    //In here is where you want to set your values for the views
    override fun onBindViewHolder(holder: SentRequestViewHolder, position: Int) {
        val currentUser = users[position]

        holder.userImage.drawable = currentUser.drawable
        holder.userFullName.text = currentUser.name
    }

    //You must override this method as well for the adapter to work properly
    override fun getItemCount() = users.size
}

你必须在使用 RecyclerView.Adapter 时重写这些方法

这里是 user_list_item.xml

<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="100dp">

    <ImageView
        android:id="@+id/userImage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <TextView
        android:id="@+id/userName"
        android:layout_below="@id/userImage"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

 </RelativeLayout>