Android 使用带有 PageAdapter 的绑定类？答案

【问题标题】：Android using Binding classes with PageAdapter?Android 使用带有 PageAdapter 的绑定类？
【发布时间】：2021-02-07 18:44:55
【问题描述】：

我的布局landing_item.xml

<androidx.appcompat.widget.LinearLayoutCompat
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".landing.MainActivity">

    <com.google.android.material.textview.MaterialTextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <com.google.android.material.textview.MaterialTextView
        android:id="@+id/description"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <ImageView
        android:id="@+id/image"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</androidx.appcompat.widget.LinearLayoutCompat>

片段

class LandingItemFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View = inflater.inflate(R.layout.landing_item, container, false)
}

适配器

class LandingItemPageAdapter(fa: FragmentActivity) : FragmentStateAdapter(fa) {
    override fun getItemCount(): Int = 3

    override fun createFragment(position: Int): Fragment = LandingItemFragment()

    override fun onBindViewHolder(
        holder: FragmentViewHolder,
        position: Int,
        payloads: MutableList<Any>
    ) {
        super.onBindViewHolder(holder, position, payloads)
        val binder = LandingItemBinding.bind(holder.itemView)
        binder.title.text = "Test"
        binder.description.text = "This is a test"
    }
}

调用 bind 时会因为找不到元素而崩溃

2021-02-07 10:40:05.183 8904-8904/com.comp.app E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.comp.app, PID: 8904
    java.lang.NullPointerException: Missing required view with ID: com.comp.app/description
        at com.comp.app.databinding.LandingItemBinding.bind(LandingItemBinding.java:88)

【问题讨论】：

标签： android android-viewbinding

【解决方案1】：

您需要将项目布局包装在<layout>标签中

<layout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools">

    <androidx.appcompat.widget.LinearLayoutCompat
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".landing.MainActivity">

        <com.google.android.material.textview.MaterialTextView
            android:id="@+id/title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

        <com.google.android.material.textview.MaterialTextView
            android:id="@+id/description"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

        <ImageView
            android:id="@+id/image"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    </androidx.appcompat.widget.LinearLayoutCompat>

</layout>

【讨论】：