我有一个名为“机会”的类的列表，其中填充了扩展“机会”的对象。该列表可以具有CommunityOpportunites或SponsorshipOpportunities。
我重写getItemViewType并根据相关位置中对象的子类为每个项目分配一个值，并对每个项目使用不同的ViewHolder:
override fun getItemViewType(position: Int): Int {
return if (opportunityList[position] is SponsorshipOpportunity){
Log.i(TAG,"Item type is sponsorshipId")
SPONSORSHIP
} else{
Log.i(TAG,"Item type is community")
COMMUNITY
}
}
inner class CommunityViewHolder(var view: CommunityTileBinding):RecyclerView.ViewHolder(view.root)
inner class SponsorshipViewHolder(var view: SponsorshipTileBinding):RecyclerView.ViewHolder(view.root)
companion object{
private const val COMMUNITY = 0
private const val SPONSORSHIP = 1
}
在onCreateViewHolder()中，为项目的类创建正确的ViewHolder，在onBindViewHolder()中，我尝试将列表中的项目(在构造函数中为Opportunity类型)转换为 View 中项目的子类:
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val inflater = LayoutInflater.from(parent.context)
return when (viewType){
COMMUNITY->CommunityViewHolder(DataBindingUtil.inflate(inflater, R.layout.community_tile, parent, false))
SPONSORSHIP-> SponsorshipViewHolder(DataBindingUtil.inflate(inflater, R.layout.sponsorship_tile, parent, false))
else-> throw IllegalArgumentException()
}
}
override fun getItemCount(): Int = opportunityList.size
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
when(holder.itemViewType){
COMMUNITY-> {
(holder as CommunityViewHolder).view.communityOpportunity = opportunityList[position] as CommunityOpportunity
}
SPONSORSHIP->{
(holder as SponsorshipViewHolder).view.sponsorship = opportunityList[position] as SponsorshipOpportunity
holder.view.postActionText.text = context.resources.getString(R.string.watch_respond)
}
}
}
但是，我得到以下类强制转换异常
java.lang.ClassCastException: com.example.model.Opportunity cannot be cast to com.example.model.CommunityOpportunity
当我尝试onBindViewHolder中的相关行时，即使打印了确认该项目是getItemViewType()中的CommunityOpportunity的日志语句。
有没有更好的方法问我，还是有更好的方法让我在RecyclerView中显示多个ViewHolder / Object类型？
编辑:这是相关的xml布局:
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="sponsorship"
type="com.example.weare8sample.model.SponsorshipOpportunity"/>
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:elevation="2dp"
android:orientation="vertical"
android:background="@drawable/tile_background">
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:foreground="@drawable/tile_background"
android:imageUrl="@{sponsorship.coverTileUri}">
</ImageView>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:gravity="center_vertical"
android:padding="10dp">
<TextView
android:id="@+id/postActionText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:fontFamily="@font/lato_bold"
tools:text="@string/watch_respond">
</TextView>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:src="@drawable/ic_chevron_right_black_36dp">
</ImageView>
</RelativeLayout>
</LinearLayout>
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="communityOpportunity"
type="com.example.weare8sample.model.CommunityOpportunity" />
</data>
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:background="@drawable/tile_background"
android:imageUrl="@{communityOpportunity.mediaImageUri}">
</ImageView>
最佳答案
在getItemViewType中为所有类型添加显式类型检查，如果类型未知，则抛出该异常，以正确处理所有情况。
现在，如果存在第三种商机，则将其视为COMMUNITY类型。
关于android - 将类转换为Kotlin的子类，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/60936738/