1. 视图绑定ViewBinding与数据绑定DataBinding
ViewBinding库会为每个xxx_layout.xml文件生成一个XxxLayoutBinding.java文件(除非声明了tools:viewBindingIgnore="true"),此类文件的成员变量包含了xml中所有声明了android:id的控件,与DataBinding不同的是,它对原有xml文件不具有侵入性,而DataBinding需要用<layout>标签包裹原布局,因此,如果你不想引入数据绑定,但又想简化findViewById这类模板代码,采用ViewBinding再好不过。
本文不讨论如何在Activity和Fragment中使用ViewBinding,只讨论在RecyclerView Adapter中的使用
2. 启用视图绑定
// 文件名 build.gradle (:app)
android {
...
buildFeatures {
viewBinding = true
}
}
3. 封装Adapter
// 文件名 CommonRvAdapter.kt
/**
* @description: recyclerView的Adapter的简单封装, 仅针对单类型viewType
*
* @param E: 列表数据实体类
* @param V: item的xml文件对应的Binding类
**/
abstract class CommonRvAdapter<E : Any, V : ViewBinding> : RecyclerView.Adapter<CommonRvHolder<V>>() {
/**
* 数据源
*/
open var data: MutableList<E> = mutableListOf()
set(value) {
field = value
notifyItemRangeChanged(0, value.size)
}
// 为什么不把这个方法也封装起来? 因为不想使用反射~
abstract override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CommonRvHolder<V>
override fun getItemCount(): 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) {
}
4. 使用案例
假设有布局文件item_student.xml布局文件, 其中只有一个TextView用来显示学生姓名
<?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="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="学生姓名"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
假设有学生实体类Student.kt
class Student {
var name: String = ""
}
重点: 根据Binding类和实体类创建Adapter
class StudentAdapter : CommonRvAdapter<Student, ItemStudentBinding>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CommonRvHolder<ItemStudentBinding> {
// 使用Binding类解析布局设置到Holder上
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) {
// binding对象中包含有所有的控件, bean对象包含有所有的实体属性
binding.tvStudentName.text = bean.name
binding.root.setOnClickListener {
ToastUtils.showShort("你点击了${bean.name}同学")
}
}
}
填充数据
val students = mutableListOf<Student>()
for (i in 0 until 100) {
students.add(Student().apply { name = "同学$i" })
}
adapter.data = students
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