Android Kotlin动态填充ExpandableListView问题及图片添加咨询

我正在学习Android的Kotlin/UI设计基础，尝试从数据库动态填充ExpandableListView。目前在displayInventory函数中调用elv.addView(txtView)时出现addView(View) is not supported in AdapterView错误。通过相关帖子了解到不能直接向ListView添加项，需向Adapter添加数据再设置到ListView，但仍难以将该概念转化为Kotlin代码实现。

疑问 #

1. 是否可以通过我尝试的这种函数方式动态填充ExpandableListView？
2. 如果后续要给ExpandableListView添加图片，是否容易实现？

CustomExpandableListAdapter类 #

class CustomExpandableListAdapter internal constructor(
    private val context: Context,
    private val titleList: List<String>,
    private val dataList: HashMap<String, List<Inventory>>
) : BaseExpandableListAdapter() {

private val inflater: LayoutInflater = LayoutInflater.from(context)
private lateinit var groupBinding: ListGroupBinding
private lateinit var itemBinding: ListItemBinding

override fun getChild(listPosition: Int, expandedListPosition: Int): Any {
    return this.dataList[this.titleList[listPosition]]!![expandedListPosition]
}

override fun getChildId(listPosition: Int, expandedListPosition: Int): Long {
    return expandedListPosition.toLong()
}

override fun getChildView(
    listPosition: Int,
    expandedListPosition: Int,
    isLastChild: Boolean,
    view: View?,
    parent: ViewGroup
): View {
    var convertView = view
    val holder: ItemViewHolder
    if (convertView == null) {
        itemBinding = ListItemBinding.inflate(inflater)
        convertView = itemBinding.root
        holder = ItemViewHolder()
        holder.label = itemBinding.expandedListItem
        convertView.tag = holder
    } else {
        holder = convertView.tag as ItemViewHolder
    }
    val expandedListText = getChild(listPosition, expandedListPosition) as String
    holder.label!!.text = expandedListText
    return convertView
}

override fun getChildrenCount(listPosition: Int): Int {
    return this.dataList[this.titleList[listPosition]]!!.size
}

override fun getGroup(listPosition: Int): Any {
    return this.titleList[listPosition]
}

override fun getGroupCount(): Int {
    return this.titleList.size
}

override fun getGroupId(listPosition: Int): Long {
    return listPosition.toLong()
}

override fun getGroupView(
    listPosition: Int,
    isExpanded: Boolean,
    view: View?,
    parent: ViewGroup
): View {
    var convertView = view
    val holder: GroupViewHolder
    if (convertView == null) {
        groupBinding = ListGroupBinding.inflate(inflater)
        convertView = groupBinding.root
        holder = GroupViewHolder()
        holder.label = groupBinding.listTitle
        convertView.tag = holder
    } else {
        holder = convertView.tag as GroupViewHolder
    }
    val listTitle = getGroup(listPosition) as String
    holder.label!!.text = listTitle
    return convertView
}

override fun hasStableIds(): Boolean {
    return false
}

override fun isChildSelectable(listPosition: Int, expandedListPosition: Int): Boolean {
    return true
}

inner class ItemViewHolder {
    internal var label: TextView? = null
}

inner class GroupViewHolder {
    internal var label: TextView? = null
}
}

ProfileActivity代码 #

class ProfileActivity : AppCompatActivity() {

private var adapter: ExpandableListAdapter? = null
private lateinit var binding: ActivityProfileBinding

val database = Firebase.database
val ref = database.getReference("Users")
val mainRef = ref.child(Firebase.auth.currentUser!!.uid).child("Inventory")
val userInventory : MutableList<Inventory> = ArrayList()
var listData = HashMap<String, List<Inventory>>()


//check hashmap for functionality and next steps to populate expandable list view
override fun onCreate(savedInstanceState: Bundle?) {

    super.onCreate(savedInstanceState)
    binding = ActivityProfileBinding.inflate(layoutInflater)
    val view = binding.root
    setupExpandableListView()
    setContentView(view)
    val layout : ConstraintLayout = findViewById(R.id.root)

    //profile pic header
    val profilePic : ImageView = findViewById(R.id.profile_pic)
    profilePic.setImageResource(R.drawable.bermanologylogo)

    //Nav Bar items
    var bottomNavView: BottomNavigationView = findViewById(R.id.bottom_nav)
    bottomNavView.selectedItemId = R.id.profile
    bottomNavView.setOnNavigationItemSelectedListener { rock ->
        when (rock.itemId) {
            R.id.profile -> {
                val intent =
                    Intent(this, ProfileActivity::class.java)
                intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
                startActivity(intent)
                finish()
            }
            R.id.feed -> {
                val intent =
                    Intent(this, SearchActivity::class.java)
                intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
                startActivity(intent)
                finish()

            }
            R.id.add_entry -> {
                val intent =
                    Intent(this, MainActivity::class.java)
                intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
                startActivity(intent)
                finish()
            }
        }
        true
    }


    //coroutines to get database contents and display inventory
    GlobalScope.launch {
        var scrollScreen : NestedScrollView = findViewById(R.id.scrolly)

        withContext(Dispatchers.IO) {
            getDB()
            listData = sortElements(userInventory) as HashMap<String, List<Inventory>>
            print(userInventory.toString())
            for ((key, value) in listData) {
                println("${key.toString()} = ${value.toString()}")
            }
        }
        withContext(Dispatchers.Main){
            displayInventory()
        }
    }

    profilePic.setOnClickListener {

        }


    }


//create and display textviews of current inventory
private fun displayInventory(){

    var elv : ExpandableListView = findViewById(R.id.elv)

    userInventory.forEach { element ->
        var uId = element.Uid.toString()
        var name = element.name.toString()
        var purchDate = element.purchDate.toString()
        var country = element.country.toString()
        var local = element.local.toString()
        var mine = element.mine.toString()
        var weight = element.weight.toString()
        var paid = element.paid.toString()
        var asking = element.asking.toString()
        var description = element.description.toString()
        var dimensions = element.dimensions.toString()
        var filePaths: ArrayList<String> = element.filePaths
        var downloadUrls: ArrayList<String> = element.downloadUrls

        val txtView = TextView(this)
        txtView.text = "Uid: $name\n" +
                "purchase date: $purchDate\n" +
                "country: $country\n" +
                "local: $local\n" +
                "mine: $mine\n" +
                "weight: $weight\n" +
                "paid: $paid\n" +
                "asking: $asking\n" +
                "UId: $uId\n" +
                "dimension: $dimensions\n" +
                "FilePaths:     ${filePaths.toString()}\n" +
                "downloadUrls: ${downloadUrls.toString()}\n"
        txtView.setTextColor(Color.BLUE)
        txtView.textSize = 25F

        elv.addView(txtView)
    }
}


/* program populates array with all of users inventory */
private suspend fun getDB() {
    mainRef.addValueEventListener(object : ValueEventListener {
        override fun onDataChange(snapshot: DataSnapshot) {

            val rockTypes = snapshot!!.children


                // This returns the correct child count...
//                println(" Outer count: " + snapshot.children.count().toString())
                rockTypes.forEach { parent ->
                    var specimens = parent.children
//                    val specName = parent.key
//                    val specCount = parent.children.count()
//                    val
//
////                    println("Inner count: " + parent.children.count().toString())
                specimens.forEach { child ->
                    var rock = child.getValue(Inventory::class.java)!!
                    println(rock.name)
                    userInventory.add(rock)
                }
            }
        }


        override fun onCancelled(error: DatabaseError) {
            TODO("Not yet implemented")
        }
    })
    delay(10000)
}


private fun sortElements(input: List<Inventory>) = input.groupBy { it.name }

private fun setupExpandableListView() {
    val names = ArrayList(listData.keys)
    val expandableListView = binding.elv

    adapter = CustomExpandableListAdapter(this, names, listData)
    expandableListView.setAdapter(adapter)

    expandableListView.setOnGroupExpandListener { groupPosition ->
        Toast.makeText(
            applicationContext,
            (listData as ArrayList<String>)[groupPosition] + " List Expanded.",
            Toast.LENGTH_SHORT
        ).show()
    }

    expandableListView.setOnGroupCollapseListener { groupPosition ->
        Toast.makeText(
            applicationContext,
            (listData as ArrayList<String>)[groupPosition] + " List Collapsed.",
            Toast.LENGTH_SHORT
        ).show()
    }

    expandableListView.setOnChildClickListener { parent, v, groupPosition, childPosition, id ->
        Toast.makeText(
            applicationContext,
            "Clicked: " + (listData as ArrayList<String>)[groupPosition] + " -> " + listData[(listData as ArrayList<String>)[groupPosition]]!!.get(
                childPosition
            ),
            Toast.LENGTH_SHORT
        ).show()
        false
    }
}
}

问题1：动态填充ExpandableListView的正确方式 #

你尝试的直接调用elv.addView()的方式完全不可行，因为ExpandableListView属于AdapterView子类，所有AdapterView都必须通过Adapter管理数据与视图绑定，不能直接添加子View。

正确实现步骤：

1. 删除displayInventory函数，不需要手动创建TextView添加到列表。
2. 修改CustomExpandableListAdapter，将数据成员改为可变类型并添加更新方法：

   class CustomExpandableListAdapter internal constructor(
       private val context: Context,
       var titleList: List<String>, // 改为var
       var dataList: HashMap<String, List<Inventory>> // 改为var
   ) : BaseExpandableListAdapter() {
   
       // ... 保留原有其他代码 ...
   
       // 添加数据更新方法
       fun updateData(newTitleList: List<String>, newDataList: HashMap<String, List<Inventory>>) {
           titleList = newTitleList
           dataList = newDataList
           notifyDataSetChanged() // 通知列表刷新视图
       }
   
       // 修正getChildView的类型转换错误，直接使用Inventory对象拼接文本
       override fun getChildView(
           listPosition: Int,
           expandedListPosition: Int,
           isLastChild: Boolean,
           view: View?,
           parent: ViewGroup
       ): View {
           var convertView = view
           val holder: ItemViewHolder
           if (convertView == null) {
               itemBinding = ListItemBinding.inflate(inflater)
               convertView = itemBinding.root
               holder = ItemViewHolder()
               holder.label = itemBinding.expandedListItem
               convertView.tag = holder
           } else {
               holder = convertView.tag as ItemViewHolder
           }
           val inventory = getChild(listPosition, expandedListPosition) as Inventory
           val itemText = "Uid: ${inventory.Uid}\n" +
                   "purchase date: ${inventory.purchDate}\n" +
                   "country: ${inventory.country}\n" +
                   "local: ${inventory.local}\n" +
                   "mine: ${inventory.mine}\n" +
                   "weight: ${inventory.weight}\n" +
                   "paid: ${inventory.paid}\n" +
                   "asking: ${inventory.asking}\n" +
                   "dimension: ${inventory.dimensions}"
           holder.label!!.text = itemText
           holder.label!!.setTextColor(Color.BLUE)
           holder.label!!.textSize = 25F
           return convertView
       }
   }
   

3. 在ProfileActivity中添加列表更新函数：

   private fun updateExpandableList() {
       val names = ArrayList(listData.keys)
       // 更新已有Adapter或创建新Adapter
       adapter?.let {
           (it as CustomExpandableListAdapter).updateData(names, listData)
       } ?: run {
           adapter = CustomExpandableListAdapter(this, names, listData)
           binding.elv.adapter = adapter
       }
   }
   

4. 修正getDB函数，移除不必要的协程和延迟，直接在Firebase回调中处理数据并更新列表：

   private fun getDB() {
       mainRef.addValueEventListener(object : ValueEventListener {
           override fun onDataChange(snapshot: DataSnapshot) {
               userInventory.clear()
               snapshot.children.forEach { parent ->
                   parent.children.forEach { child ->
                       val rock = child.getValue(Inventory::class.java)!!
                       userInventory.add(rock)
                   }
               }
               listData = sortElements(userInventory) as HashMap<String, List<Inventory>>
               updateExpandableList() // 主线程直接更新列表
           }
   
           override fun onCancelled(error: DatabaseError) {
               Toast.makeText(this@ProfileActivity, "加载数据失败", Toast.LENGTH_SHORT).show()
           }
       })
   }
   

5. 在onCreate中直接调用getDB()，不需要GlobalScope协程。

问题2：给ExpandableListView添加图片的实现 #

非常容易实现，只需修改布局和Adapter代码：

1. 修改子项布局list_item.xml，添加ImageView：

   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:orientation="horizontal"
       android:padding="16dp">
   
       <ImageView
           android:id="@+id/item_image"
           android:layout_width="80dp"
           android:layout_height="80dp"
           android:scaleType="centerCrop"
           android:src="@drawable/placeholder"/>
   
       <TextView
           android:id="@+id/expanded_list_item"
           android:layout_width="match_parent"
           android:layout_height="wrap_content"
           android:layout_marginStart="16dp"/>
   </LinearLayout>
   

2. 更新Adapter的ItemViewHolder和getChildView：

   inner class ItemViewHolder {
       internal var label: TextView? = null
       internal var image: ImageView? = null // 添加ImageView引用
   }
   
   override fun getChildView(
       listPosition: Int,
       expandedListPosition: Int,
       isLastChild: Boolean,
       view: View?,
       parent: ViewGroup
   ): View {
       var convertView = view
       val holder: ItemViewHolder
       if (convertView == null) {
           itemBinding = ListItemBinding.inflate(inflater)
           convertView = itemBinding.root
           holder = ItemViewHolder()
           holder.label = itemBinding.expandedListItem
           holder.image = itemBinding.itemImage // 初始化ImageView
           convertView.tag = holder
       } else {
           holder = convertView.tag as ItemViewHolder
       }
       val inventory = getChild(listPosition, expandedListPosition) as Inventory
       // 拼接文本...
       holder.label!!.text = itemText
       // 加载图片（需引入Glide库）
       if (inventory.downloadUrls.isNotEmpty()) {
           Glide.with(context)
               .load(inventory.downloadUrls[0])
               .placeholder(R.drawable.placeholder)
               .into(holder.image!!)
       } else {
           holder.image!!.setImageResource(R.drawable.no_image)
       }
       return convertView
   }
   

3. 在app模块的build.gradle中添加Glide依赖：

   dependencies {
       implementation 'com.github.bumptech.glide:glide:4.16.0'
       annotationProcessor 'com.github.bumptech.glide:compiler:4.16.0'
   }
   

内容的提问来源于stack exchange，提问作者Learning_slow