如何每5秒更新一次ViewPager2

Question

我需要在Viewpager2中不断更新数据我这样做，每五秒呼叫一次

adapter?.updateData(it)      
fun updateData(items: List<TestDataObject>) {
list = items
notifyDataSetChanged()
}

问题是页面在notifyDataSetChange之后显示错误的文本我认为问题是在notifyDataSetChange，但我不知道如何修复它。

• 完整代码github
• 视频演示问题photos.google.com

MainActivity

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.lifecycleScope
import by.lwo.viewpagertest.databinding.ActivityMainBinding
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch

class MainActivity : AppCompatActivity() {

lateinit var binding: ActivityMainBinding
private var adapter: ViewPagerAdapter? = null
val testList: MutableList<TestDataObject> = emptyList<TestDataObject>().toMutableList()

private val _testLiveData = MutableLiveData<Event<List<TestDataObject>>>()

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
setDataToList()
setAdapter()
constantlyUpdateList()

_testLiveData.observeEvent(this) {
adapter?.updateData(it)
constantlyUpdateList()
}

}

private fun constantlyUpdateList() {
lifecycleScope.launch {
delay(5000)
setDataToList()
_testLiveData.value = Event(testList)
}
}

private fun setDataToList() {
testList.clear()
repeat(6) {
testList.add(
TestDataObject(
titleText = "title for page $it",
infoText = "infoText for page $it"
)
)
}
}

private fun setAdapter(){
binding.apply {
adapter = ViewPagerAdapter(testList)
viewPager.adapter = adapter
viewPager.offscreenPageLimit = testList.size
}
}
}

适配器

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.recyclerview.widget.RecyclerView
import by.lwo.viewpagertest.databinding.HolderTestBinding
class ViewPagerAdapter(var list: List<TestDataObject>) : RecyclerView.Adapter<ViewPagerAdapter.TestHolder>() {
lateinit var binding: HolderTestBinding
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewPagerAdapter.TestHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.holder_test, parent, false)
binding = DataBindingUtil.bind(view)!!
return TestHolder(view)
}
override fun onBindViewHolder(holder: ViewPagerAdapter.TestHolder, position: Int) {
holder.bind(list[position])
}
override fun getItemCount(): Int = list.size
fun updateData(items: List<TestDataObject>) {
list = items
notifyDataSetChanged()
}
inner class TestHolder(containerView: View) : RecyclerView.ViewHolder(containerView) {
fun bind(testDataObject: TestDataObject) {
binding.apply {
titleTv.text = testDataObject.titleText
textTv.text = testDataObject.infoText
}
}
}
}
data class TestDataObject(val titleText: String = "", val infoText: String = "")

Answer 1

我看到两个主要问题:

1. notifyDataSetChanged方法将强制你的适配器重新渲染你的活动上的所有项目。您的列表与新列表仅在一个元素上有所不同并不重要:它将在整体上重新呈现。
   我建议使用ListAdapter，它将使用submitList方法处理您的设置。它是优化的用例，您将经常更新您的列表。

2. 最重要的是，适配器的构建方式。你有属性:

lateinit var binding: HolderTestBinding

在每次onCreateViewHolder调用中设置。然而，它是一个类字段，每次设置时，旧的持有人的引用将丢失，在每个TestHolder实例中，您将引用最后一个膨胀的绑定，因此，所有的视图持有人将引用完全相同的视图持有人，而不是他们自己的。
更好的方法是将绑定传递给每个holder的构造函数:

class ViewPagerAdapter(...) : ListAdapter(...) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewPagerAdapter.TestHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.holder_test, parent, false)
val holder = DataBindingUtil.bind(view)?.let {
TestHolder(it)
}
return holder!!
}
// 'inner' modifier is not needed
class TestHolder(private val binding: TestHolderBinding) : RecyclerView.ViewHolder(binding.root) {
fun bind(testDataObject: TestDataObject) {
// this 'binding' will reference their own binding, and not the 'global' one :)
binding.apply {
titleTv.text = testDataObject.titleText
textTv.text = testDataObject.infoText
}
}
}
}