RecyclerViewでアイテム数に応じて高さを変更したい

RecyclerViewのheightをアイテム数に応じて動的に変更したいのですが、アイテムの高さ取得などからわからないです。どのように書けばいいのか教えて頂きたいです。

XML
1<?xml version="1.0" encoding="utf-8"?>
2<androidx.constraintlayout.widget.ConstraintLayout
3            android:layout_width="match_parent"
4            android:layout_height="match_parent"
5            android:background="#e0e0e0">
6<androidx.recyclerview.widget.RecyclerView
7                android:id="@+id/trainerListRecycerView"
8                android:layout_width="match_parent"
9                android:layout_height="500dp"
10                app:layoutManager="androidx.recyclerview.widget.GridLayoutManager"
11                app:layout_constraintEnd_toEndOf="parent"
12                app:layout_constraintHorizontal_bias="0.0"
13                app:layout_constraintStart_toStartOf="parent"
14                app:layout_constraintTop_toTopOf="parent" />
15</androidx.constraintlayout.widget.ConstraintLayout>
16

Kotlin
1//フラグメント
2class TrainerListFragment : Fragment() {
3
4    private lateinit var trainerListViewModel: TrainerListViewModel
5    private lateinit var recyclerView: RecyclerView
6    private lateinit var trainerList: ArrayList<TrainerListAdapter.TrainerListItem>
7    private lateinit var trainerListAdapter: TrainerListAdapter
8
9    override fun onCreateView(
10        inflater: LayoutInflater, container: ViewGroup?,
11        savedInstanceState: Bundle?
12    ): View? {
13        trainerListViewModel =
14            ViewModelProvider(this).get(TrainerListViewModel::class.java)
15        val root = inflater.inflate(R.layout.list_trainer, container, false)
16
17
18
19        val testTrainer1 = TrainerListAdapter.TrainerListItem(R.drawable.ic_home, "トレーナー１", 1, 1, "カテゴリ１", "カテゴリ２")
20        val testTrainer2 = TrainerListAdapter.TrainerListItem(R.drawable.ic_calendar, "トレーナー２", 2, 2, "カテゴリ３", "カテゴリ４")
21        val testTrainer3 = TrainerListAdapter.TrainerListItem(R.drawable.ic_search, "トレーナー３", 2, 2, "カテゴリ５", "カテゴリ６")
22
23        trainerList = arrayListOf(testTrainer1, testTrainer2, testTrainer3)
24
25        recyclerView = root.findViewById(R.id.trainerListRecycerView)
26        trainerListAdapter =
27            TrainerListAdapter(
28                trainerList
29            )
30        recyclerView.adapter = trainerListAdapter
31        recyclerView.isNestedScrollingEnabled = false
32        recyclerView.layoutManager = GridLayoutManager(activity,2)
33        return root
34    }
35
36}

Kotlin
1//アダプター
2class TrainerListAdapter(private val trainerList: ArrayList<TrainerListItem>): RecyclerView.Adapter<TrainerListAdapter.ViewHolder>() {
3
4    data class TrainerListItem(
5        val image: Int,
6        val name: String,
7        val subscribedNumber: Int,
8        val rank: Int,
9        val category1: String,
10        val category2: String
11    )
12
13    // Viewの初期化
14    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
15        val image: ImageView = view.findViewById(R.id.trainerListItemImage)
16        val name: TextView = view.findViewById(R.id.trainerListItemName)
17        val subscribedNumber: TextView = view.findViewById(R.id.trainerListSubscribedNumber)
18        val rank: TextView = view.findViewById(R.id.trainerListRankNumber)
19        val category1: TextView = view.findViewById(R.id.trainerListItemCategory1)
20        val category2: TextView = view.findViewById(R.id.trainerListItemCategory2)
21    }
22
23    // レイアウトの設定
24    override fun onCreateViewHolder(viewGroup: ViewGroup, viewType: Int): ViewHolder {
25        val view = LayoutInflater.from(viewGroup.context).inflate(R.layout.item_trainer, viewGroup, false)
26        return ViewHolder(
27            view
28        )
29    }
30
31    // Viewの設定
32    override fun onBindViewHolder(viewHolder: ViewHolder, position: Int) {
33        val trainer = trainerList[position]
34
35        viewHolder.image.setBackgroundResource(trainer.image)
36        viewHolder.name.text = trainer.name
37        viewHolder.subscribedNumber.text = trainer.subscribedNumber.toString()
38        viewHolder.rank.text = trainer.rank.toString()
39        viewHolder.category1.text = trainer.category1
40        viewHolder.category2.text = trainer.category2
41
42
43        viewHolder.itemView.setOnClickListener { v -> //ここにアイテムをクリックした際の挙動を記載
44            // activityを取得
45            val activity = v!!.context as TopActivity
46            // DetailFragmentを取得
47            val detail = DetailFragment()
48
49            activity.supportFragmentManager.beginTransaction().setCustomAnimations(R.anim.slide_in_right,R.anim.slide_out_left, R.anim.slide_in_left, R.anim.slide_out_right).replace(R.id.trainer_replace, detail).addToBackStack(null).commit()
50
51
52        }
53    }
54
55    // 表示数を返す
56    override fun getItemCount() = trainerList.size
57}

行動規範の内容に同意します

回答1件

自己解決

onCreateViewの中に書いてしまうとview設置前に高さを図ることになり、エラーが出ました。
そこでafterMeasuredという拡張関数でview設置後に高さを測ることで解決しました。
参考にしたサイトは以下です
http://android-note.open-memo.net/sub/other_view__get_view_size.html
https://qiita.com/titoi2/items/7bf271cd17beae74620b

Kotlin
1inline fun <T : View> T.afterMeasured(crossinline f: T.() -> Unit) {
2    viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
3        override fun onGlobalLayout() {
4            if (measuredWidth > 0 && measuredHeight > 0) {
5                viewTreeObserver.removeOnGlobalLayoutListener(this)
6                f()
7            }
8        }
9    })
10}
11
12class TrainerListFragment : Fragment() {
13
14    private lateinit var trainerListViewModel: TrainerListViewModel
15    private lateinit var recyclerView: RecyclerView
16    private lateinit var trainerList: ArrayList<TrainerListAdapter.TrainerListItem>
17    private lateinit var trainerListAdapter: TrainerListAdapter
18
19    override fun onCreateView(
20        inflater: LayoutInflater, container: ViewGroup?,
21        savedInstanceState: Bundle?
22    ): View? {
23        trainerListViewModel =
24            ViewModelProvider(this).get(TrainerListViewModel::class.java)
25        val root = inflater.inflate(R.layout.list_trainer, container, false)
26
27        val testTrainer1 = TrainerListAdapter.TrainerListItem(R.drawable.ic_home, "トレーナー１", 1, 1, "カテゴリ１", "カテゴリ２")
28        val testTrainer2 = TrainerListAdapter.TrainerListItem(R.drawable.ic_calendar, "トレーナー２", 2, 2, "カテゴリ３", "カテゴリ４")
29        val testTrainer3 = TrainerListAdapter.TrainerListItem(R.drawable.ic_search, "トレーナー３", 2, 2, "カテゴリ５", "カテゴリ６")
30
31
32
33        trainerList = arrayListOf(testTrainer1, testTrainer2, testTrainer3)
34        recyclerView = root.findViewById(R.id.trainerListRecycerView)
35        trainerListAdapter =
36            TrainerListAdapter(
37                trainerList
38            )
39        recyclerView.adapter = trainerListAdapter
40        recyclerView.layoutManager = GridLayoutManager(activity,2)
41
42
43        recyclerView.afterMeasured {
44            val listItem = recyclerView.getChildAt(0)
45            val itemHeight = listItem.height
46            val totalHeight = itemHeight * recyclerView.childCount
47            layoutParams.height = totalHeight
48        }
49
50        return root
51    }
52
53
54}