除非添加绝对尺寸，否则不显示约束布局的问题

Question

我有此布局，并尝试根据位置打开相应的LL。但是，只有当我在绝对尺寸（例如200dp）的宽度内提供文本视图时，才会显示并绘制第一个线性布局，并且我也尝试了带有约束的0dp。

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/draft_rider_container"
android:layout_width="match_parent"
android:layout_height="100dp"
android:background="#000000"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">

<LinearLayout
    android:id="@+id/header"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="30dp"
        android:text="lost"
        android:textColor="@android:color/white"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</LinearLayout>

<LinearLayout
    android:id="@+id/section"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    android:orientation="horizontal"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    android:visibility="gone">

    <TextView
        android:id="@+id/fake"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAlignment="center"
        tools:text="Andrea Dovizioso's"></TextView>

</LinearLayout>

<LinearLayout
    android:id="@+id/row"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    android:visibility="gone">

    <TextView
        android:id="@+id/rider_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAlignment="center"
        tools:text="Andrea Dovizioso's"></TextView>

</LinearLayout>

此布局是从位于我的片段上的回收者视图呈现的，它是这样放置的：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".roster.RosterFragment">

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/player_rider_list"
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:background="#ffffff"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<com.google.android.material.floatingactionbutton.FloatingActionButton
    android:layout_width="56dp"
    android:layout_height="56dp"
    android:layout_marginRight="15dp"
    android:layout_marginBottom="15dp"
    android:src="@drawable/baseline_edit_white_24dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:rippleColor="@color/colorPrimary" />

这是我的适配器：

class PlayerRidersAdapter :  RecyclerView.Adapter<PlayerRidersAdapter.ViewHolder>() {

var riderList = ArrayList<Rider>()

override fun onCreateViewHolder(parent: ViewGroup, position: Int): ViewHolder {
    val view = LayoutInflater.from(parent.context).inflate(R.layout.rider_item_layout, null, false)
    return ViewHolder(view)
}

override fun getItemCount(): Int {
    return riderList.count() + 2
}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    when(position) {
        0 -> showHeader(holder)
        3 -> showSection(holder)
        else -> showRow(holder)
    }
}

fun showHeader(holder: ViewHolder) {
    holder.headerContainer.visibility = View.VISIBLE
    holder.sectionContainer.visibility = View.GONE
    holder.rowContainer.visibility = View.GONE
}

fun showRow(holder: ViewHolder) {
    holder.headerContainer.visibility = View.GONE
    holder.sectionContainer.visibility = View.GONE
    holder.rowContainer.visibility = View.VISIBLE

    //holder.name.text = rider.name
}

fun showSection(holder: ViewHolder) {
    holder.headerContainer.visibility = View.GONE
    holder.sectionContainer.visibility = View.VISIBLE
    holder.rowContainer.visibility = View.GONE
}

fun addRiders(riders : ArrayList<Rider>){
    riderList.addAll(riders)
    notifyDataSetChanged()
}

class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
    var headerContainer = view.findViewById<LinearLayout>(R.id.header)
    var sectionContainer = view.findViewById<LinearLayout>(R.id.section)
    var rowContainer = view.findViewById<LinearLayout>(R.id.row)
    var name = view.findViewById<TextView>(R.id.rider_name)
}
}

Answer 1

在您的适配器中，在onCreateViewHolder（）中指定以下内容：

val view = LayoutInflater.from(parent.context).inflate(R.layout.rider_item_layout, parent, false)

指定root参数将使膨胀后的布局正确调整大小。这很可能是您的问题。

但是，match_parent在ConstraintLayout中使用时有时会出现奇怪的行为，因此请改用0dp，并记住要约束受影响的面。 ConstraintLayout可以处理这种情况，将其报告为错误，或者至少支持Lint检查。

顺便说一句：LinearLayout中包含的对[[TextViews的约束没有作用。约束仅适用于ConstraintLayout的direct个子代。