ViewBinding and DataBinding DataBinding

The ViewBinding library generates an xxxLayoutbindingbinding.java file for each xxx_Layout.xml file (unless tools:viewBindingIgnore=”true” is declared), The member variables in this type of file contain all the controls in the XML that declare android:id. Unlike DataBinding, it is not intrusive with the original XML file, which requires the <layout> tag to wrap the original layout, so if you don’t want to introduce DataBinding, But if you want to simplify template code like findViewById, a ViewBinding is a great way to do it.

This article does not discuss how to use ViewBinding in activities and fragments, only discuss the use of RecyclerView Adapter

2. Enable view binding

// File name build.gradle (:app)
android {
	...
	buildFeatures {
            viewBinding = true}}Copy the code

3. Packaging Adapter

// File name commonRvAdapter.kt
/ * * *@description: recyclerView Adapter simple encapsulation, only for single type viewType * *@paramE: List data entity class *@paramBinding class **/ for the XML file V: item
abstract class CommonRvAdapter<E : Any, V : ViewBinding> : RecyclerView.Adapter<CommonRvHolder<V>>() {
    /** * Data source */
    open var data: MutableList<E> = mutableListOf()
        set(value) {
            field = value
            notifyItemRangeChanged(0, value.size)
        }
    // Why not wrap this method as well? Because I don't want to use reflection
    abstract override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CommonRvHolder<V>
    
    override fun getItemCount(a): Int = data.size
    
    override fun onBindViewHolder(holder: CommonRvHolder<V>, position: Int) {
        onBindViewHolder(holder, holder.adapterPosition, holder.binding, data[holder.adapterPosition])
    }
    
    abstract fun onBindViewHolder(holder: CommonRvHolder<V>, position: Int, binding: V, bean: E)
}

open class CommonRvHolder<V : ViewBinding>(val binding: V) : RecyclerView.ViewHolder(binding.root) {

}
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4. Use cases

  1. Suppose you have a layout file, item_student.xml, with a single TextView that displays student names

      
<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="wrap_content"
    >

    <TextView
        android:id="@+id/tv_student_name"
        style="@style/text_2.body.dark"
        android:layout_width="0dp"
        android:layout_marginStart="20dp"
        android:layout_marginEnd="20dp"
        android:padding="10dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:text="Student name"
        />

</androidx.constraintlayout.widget.ConstraintLayout>
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  1. Let’s say I have Student entity class student.kt
class Student {
    var name: String = ""
}
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  1. Important: Create Adapter based on Binding class and entity class
class StudentAdapter : CommonRvAdapter<Student, ItemStudentBinding>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CommonRvHolder<ItemStudentBinding> {
        // Use the Binding class to parse the layout Settings into the Holder
        val inflate = ItemStudentBinding.inflate(LayoutInflater.from(parent.context), parent, false)
        return CommonRvHolder(inflate)
    }
    
    override fun onBindViewHolder(holder: CommonRvHolder<ItemStudentBinding>, position: Int, binding: ItemStudentBinding, bean: Student) {
        // The binding object contains all the controls, and the Bean object contains all the entity properties
        binding.tvStudentName.text = bean.name
        binding.root.setOnClickListener {
            ToastUtils.showShort("You clicked${bean.name}Students")}}}Copy the code
  1. Fill in the data
val students = mutableListOf<Student>()
for (i in 0 until 100) {
    students.add(Student().apply { name = "The classmate$i" })
}
adapter.data = students
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