前言

RecyclerView是一个和listView有些相似的列表结构控件，可以实现一些基本的列表的显示及事件内容

基本使用

设置item里的数据类，并且添加adapter类，设置item对应的类。
将RecyclerView控件的adapter，layoutManger进行设置。

1. 包引入

Recyclerview是一个基于support包的控件，由于目前androidx已经取代了supprot包，推荐使用Androidx包

    api 'androidx.recyclerview:recyclerview:1.1.0'

2. 在布局文件中使用

Recyclerview在activity或者fragment中需要引入使用

<?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=".MainActivity">


    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/list_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

3. item的布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:layout_marginTop="20dp"
        android:id="@+id/text_item_test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="this is a test"/>
    <Button
        android:text="测试"
        android:id="@+id/btn_item_test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

4. item数据类封装

class Data {
    var textMessage: String = "data"
    var btnText: String = "测试"
}

5. 定义adapter类和承载列表item布局的viewholder

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.demowork1.R
import com.example.demowork1.util.LogUtil

class TestAdapter(arrayData: ArrayList<TestData>) :
    RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    private var listData: List<TestData> = arrayData

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        var view: View =
            LayoutInflater.from(parent.context).inflate(R.layout.item_test_layout, parent, false)
        return  TestViewHolder1(view)
    }

    override fun getItemCount(): Int {
        return listData.size
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        if (holder is TestViewHolder1) {
            holder.textView?.text = listData[position].textMessage
            holder.btnTest?.text = listData[position].btnText
            holder.btnTest?.setOnClickListener {
                LogUtil.instance.d("点击了按钮$position")
            }
        }
    }

    class TestViewHolder1(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var textView: TextView? = null
        var btnTest: Button? = null

        init {
            textView = itemView.findViewById(R.id.text_item_test)
            btnTest = itemView.findViewById(R.id.btn_item_test)
        }
    }
}

6. Activity中设置adapter和layoutManager

RecyclerView必须在使用时定义其adapter和layoutManager，否则会产生错误或者无法显示

如果碰到了列表无法显示的情况，首先确定LayoutManager是否设置

class MainActivity : AppCompatActivity() {
    private var listView: RecyclerView? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        listView = findViewById(R.id.list_main)
        var listData = initData()
        var listEntity = ArrayList<MultiTestEntity>()
        setSimpleAdapter(listData)
    }
    //初始化数据
    private fun initData(): ArrayList<TestData> {
        var listData = ArrayList<TestData>()
        listData.add(TestData("test1", "测试1"))
        listData.add(TestData("test2", "测试2"))
        listData.add(TestData("test3", "测试3"))
        listData.add(TestData("test4", "测试4"))
        LogUtil.instance.d(listData.toString())
        return listData
    }
    //设置adapter
    private fun setSimpleAdapter(listData: ArrayList<TestData>) {
        var testAdapter = TestAdapter(listData)
        listView?.adapter = testAdapter
        //LayoutManger必须设置，否则不显示列表
        listView?.layoutManager = LinearLayoutManager(this)
    }
}

7. 多Item显示

一个RecyclerView中有多种item显示是十分常见的需求，RecyclerView支持这一需求，针对不同的类型设置不同的布局文件及ViewHolder即可。
区别类型的方法getItemViewType用来设定在不同的position上有着不同的类型item。

多Item显示adapter示例代码如下：

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import androidx.recyclerview.widget.RecyclerView
import com.example.demowork1.testbrvah.TestData

class TestAdapter(arrayData: ArrayList<TestData>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

    private var listData: List<TestData> = arrayData

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        return when (viewType) {
            TYPE_1 -> {
                var view: View =
                        LayoutInflater.from(parent.context).inflate(R.layout.item_test_layout, parent, false)
                var viewHolder = TestViewHolder1(view)
                viewHolder.btnTest?.setOnClickListener {
                    Toast.makeText(parent.context, "点击了按钮1", Toast.LENGTH_SHORT).show()
                }
                viewHolder
            }
            TYPE_2 -> {
                var view: View =
                        LayoutInflater.from(parent.context).inflate(R.layout.item2_test_layout, parent, false)
                var viewHolder = TestViewHolder2(view)
                viewHolder.btnTest?.setOnClickListener {
                    Toast.makeText(parent.context, "点击了item2按钮", Toast.LENGTH_SHORT).show()
                }
                viewHolder
            }
            else -> {
                var view: View =
                        LayoutInflater.from(parent.context).inflate(R.layout.item_test_layout, parent, false)
                var viewHolder = TestViewHolder1(view)
                viewHolder.btnTest?.setOnClickListener {
                    Toast.makeText(parent.context, "点击了按钮1", Toast.LENGTH_SHORT).show()
                }
                viewHolder
            }
        }
    }

    override fun getItemCount(): Int {
        return listData.size
    }

    override fun getItemViewType(position: Int): Int {
        return when (position % 2) {
            0 -> {
                TYPE_1
            }
            1 -> {
                TYPE_2
            }
            else -> {
                TYPE_1
            }
        }
    }
    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        when (getItemViewType(position)) {
            TYPE_1 -> {
                if (holder is TestViewHolder1) {
                    holder.textView?.text = listData[position].textMessage
                }
            }
            TYPE_2 -> {
                if (holder is TestViewHolder2) {
                    holder.textView?.text = listData[position].textMessage
                }
            }
            else -> {
                if (holder is TestViewHolder1) {
                    holder.textView?.text = listData[position].textMessage
                }
            }
        }
    }

    class TestViewHolder1(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var textView: TextView? = null
        var btnTest: Button? = null

        init {
            textView = itemView.findViewById(R.id.text_item_test)
            btnTest = itemView.findViewById(R.id.btn_item_test)
        }
    }

    class TestViewHolder2(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var textView: TextView? = null
        var btnTest: Button? = null

        init {
            textView = itemView.findViewById(R.id.text2_item_test)
            btnTest = itemView.findViewById(R.id.btn2_item_test)
        }
    }

    companion object {
        const val TYPE_1 = 1
        const val TYPE_2 = 2
    }
}

Q.E.D.

行走在天地间自由的灵魂