Android RecyclerView AsyncListDiffer DiffUtil，Kotlin（a）
Kotlin
import android.graphics.Color
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.AsyncListDiffer
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.RecyclerView
import kotlin.random.Random
const val ITEM_COUNT = 30
class MainActivity : AppCompatActivity() {
private var mAdapter: MyAdapter? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val rv = findViewById<RecyclerView>(R.id.rv)
val layoutManager = GridLayoutManager(this, 3)
rv.layoutManager = layoutManager
mAdapter = MyAdapter()
rv.adapter = mAdapter
}
override fun onResume() {
super.onResume()
val list = mutableListOf<MyItem>()
for (i in 0 until ITEM_COUNT) {
val item = MyItem()
item.pos = i
item.change = Random.Default.nextBoolean()
item.time = System.currentTimeMillis()
list.add(item)
}
mAdapter?.onChange(list)
}
class MyAdapter : RecyclerView.Adapter<MyVH> {
private var mDiffer = AsyncListDiffer(this, object : DiffUtil.ItemCallback<MyItem>() {
override fun areItemsTheSame(oldItem: MyItem, newItem: MyItem): Boolean {
return oldItem.pos == newItem.pos
}
override fun areContentsTheSame(oldItem: MyItem, newItem: MyItem): Boolean {
return oldItem == newItem
}
override fun getChangePayload(oldItem: MyItem, newItem: MyItem): Any? {
return super.getChangePayload(oldItem, newItem)
}
})
constructor() {
val list = mutableListOf<MyItem>()
for (i in 0 until ITEM_COUNT) {
val item = MyItem()
item.pos = i
item.change = false
item.time = 0L
list.add(item)
}
onChange(list)
}
fun onChange(list: MutableList<MyItem>) {
mDiffer.submitList(list)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyVH {
val view = LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_2, parent, false)
return MyVH(view)
}
override fun getItemCount(): Int {
return mDiffer.currentList.size
}
override fun onBindViewHolder(holder: MyVH, position: Int) {
holder.text1.text = "pos=${mDiffer.currentList[position].pos}"
holder.text2.text = "time=${mDiffer.currentList[position].time}"
if (mDiffer.currentList[position].change) {
holder.text1.setTextColor(Color.RED)
holder.text2.setTextColor(Color.RED)
} else {
holder.text1.setTextColor(Color.BLACK)
holder.text2.setTextColor(Color.BLACK)
}
}
}
class MyVH(itemView: View) : RecyclerView.ViewHolder(itemView) {
val text1: TextView = itemView.findViewById(android.R.id.text1)
val text2: TextView = itemView.findViewById(android.R.id.text2)
}
class MyItem {
var change = false
var pos = 0
var time = 0L
override fun equals(other: Any?): Boolean {
return pos == (other as MyItem).pos && time == other.time
}
}
}