Efficient use of RecyclerView Section 1

List-related layouts are the most integral part of the development process,And mastering some efficient skills can help us improve development efficiency at the same time,还能优化代码,Reduce redundancy andbug的产生.

1.listitem实时预览

在UI绘制时,Detail and style adjustments are unavoidable,If every adjustment goesrunCheck the effect later,inefficiency,使用listitem,operation can be avoided,直接使用AndroidStudioBuilt-in preview function for debugging
例如

<androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/rv_student" android:layout_width="match_parent" android:layout_height="match_parent" xmlns:app="http://schemas.android.com/apk/res-auto" tools:listitem="@layout/item_study" tools:context=".one.StudentActivity" />

效果如下：

2,xml中设置layoutManager

<androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/rv_student" android:layout_width="match_parent" android:layout_height="match_parent" xmlns:app="http://schemas.android.com/apk/res-auto" tools:listitem="@layout/item_study" android:orientation="vertical" app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" tools:context=".one.StudentActivity" />

It can be set directly in the layout codeLayoutManagertype and some related properties,例如方向,The number of each row in grid layout, etc.

3,Use the default dividing line

You can use the default split line style provided by the official,Reduce duplicate creation.

    //添加默认的分割线
        rv_student.addItemDecoration(DividerItemDecoration(this,
            (rv_student.layoutManager as LinearLayoutManager).orientation))

For personalization,need to base itself onItemDecoration进行定制

4,添加Item点击事件

使用Kotlin函数式的思想,Quickly add click events
1）在Adapteradd parameters to the constructor

class StudentAdapter(private val data:ArrayList<StudentInfo>,
                     private val itemClick:(StudentInfo) ->Unit):
    RecyclerView.Adapter<StudentAdapter.ViewHolder>() {
    
}

2）初始化AdapterWhen passing in the click function

    //学生数据列表
    private val studentEntities = ArrayList<StudentInfo>()
    //适配器
    private val  studentAdapter by lazy {
        StudentAdapter(studentEntities,this::onStudentItemClick)
    }

	/**
	*点击事件
	*/
    private fun onStudentItemClick(entity:StudentInfo){
        /**
         * 点击Item时,Get the user information of the current click
         */
        Log.d(TAG,"onStudentItemClick()--->$entity")
        Toast.makeText(this,"$entity",Toast.LENGTH_LONG).show()
    }

3）使用时

  itemView.setOnClickListener { itemClick(entity) }

5,Adapter中获取上下文

在onCreateViewHolder中获取context对象,Reduce the number of parameters passed during construction

  //定义上下文
    private lateinit var context:Context

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        context = parent.context
    }

The code that completes the above function is as follows：
1,item布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="16dp" xmlns:app="http://schemas.android.com/apk/res-auto">

    <androidx.appcompat.widget.AppCompatImageView android:id="@+id/iv_icon" android:layout_width="48dp" app:layout_constraintLeft_toLeftOf="parent" android:src="@mipmap/ic_launcher" app:layout_constraintTop_toTopOf="parent" app:layout_constraintBottom_toBottomOf="parent" android:layout_height="48dp"/>

    <TextView app:layout_constraintTop_toTopOf="parent" app:layout_constraintLeft_toRightOf="@+id/iv_icon" android:layout_width="wrap_content" android:id="@+id/tv_title" android:gravity="center" android:text="Study" android:textSize="22sp" android:layout_marginLeft="16dp" app:layout_constraintVertical_chainStyle="packed" app:layout_constraintBottom_toTopOf="@+id/tv_second" android:textColor="@android:color/black" android:layout_height="wrap_content"/>

    <TextView android:id="@+id/tv_subtitle" android:layout_width="wrap_content" app:layout_constraintLeft_toRightOf="@+id/iv_icon" app:layout_constraintTop_toBottomOf="@+id/tv_study" android:textSize="16sp" android:layout_marginLeft="16dp" app:layout_constraintVertical_chainStyle="packed" android:text="zhansan" android:textColor="@color/cardview_dark_background" app:layout_constraintBottom_toBottomOf="parent" android:layout_height="wrap_content"/>

    <TextView android:id="@+id/tv_gender" android:layout_width="wrap_content" android:textSize="18sp" android:text="男" android:textColor="@color/material_on_surface_emphasis_high_type" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" android:textStyle="bold" app:layout_constraintBottom_toBottomOf="parent" android:layout_height="wrap_content"/>


</androidx.constraintlayout.widget.ConstraintLayout>

2,Activity布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/rv_student" android:layout_width="match_parent" android:layout_height="match_parent" xmlns:app="http://schemas.android.com/apk/res-auto" tools:listitem="@layout/item_study" android:orientation="vertical" app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" tools:context=".one.StudentActivity" />

3,Activity代码

package com.example.recyclerviewstudy.one

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.recyclerview.widget.DividerItemDecoration
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.example.recyclerviewstudy.R
import com.example.recyclerviewstudy.StudentInfo

class StudentActivity : AppCompatActivity() {
    companion object{
        val TAG = this::class.simpleName
    }
    //学生数据列表
    private val studentEntities = ArrayList<StudentInfo>()
    //适配器
    private val  studentAdapter by lazy {
        StudentAdapter(studentEntities,this::onStudentItemClick)
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_study)
        initRecyclerView()
    }

    private fun initRecyclerView(){
        val rv_student = findViewById<RecyclerView>(R.id.rv_student)
        //添加默认的分割线
        rv_student.addItemDecoration(DividerItemDecoration(this,
            (rv_student.layoutManager as LinearLayoutManager).orientation))
        rv_student.adapter = studentAdapter
        produceData()
    }

    private fun onStudentItemClick(entity:StudentInfo){
        /**
         * 点击Item时,Get the user information of the current click
         */
        Log.d(TAG,"onStudentItemClick()--->$entity")
        Toast.makeText(this,"$entity",Toast.LENGTH_LONG).show()
    }
	
	//生产数据
    private fun produceData(){
        for (i in 0..20){
            studentEntities.add(StudentInfo("zhang san $i",i,if (i%2==0)"男" else "女"))
        }
    }
}

4,Adapter完整代码

package com.example.recyclerviewstudy.one

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.recyclerviewstudy.R
import com.example.recyclerviewstudy.StudentInfo

class StudentAdapter(private val data:ArrayList<StudentInfo>,
                     private val itemClick:(StudentInfo) ->Unit):
    RecyclerView.Adapter<StudentAdapter.ViewHolder>() {

    //定义上下文
    private lateinit var context:Context

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        context = parent.context
        return ViewHolder(LayoutInflater.from(context)
            .inflate(R.layout.item_study,parent,false),itemClick)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.bind(data[position])
    }

    override fun getItemCount() = data.size

    inner class ViewHolder(itemView:View,val itemClick:(StudentInfo) -> Unit):RecyclerView.ViewHolder(itemView){
        val tv_name:TextView = itemView.findViewById(R.id.tv_title)
        val tv_age:TextView = itemView.findViewById(R.id.tv_subtitle)
        val tv_gender:TextView = itemView.findViewById(R.id.tv_gender)
        private lateinit var entity:StudentInfo

        init {
            itemView.setOnClickListener { itemClick(entity) }
        }

        fun bind(entity:StudentInfo){
            this.entity = entity
            entity.apply {
                tv_name.text = name
                tv_age.text = "$age"
                tv_gender.text = gander
            }
        }
    }
}

针对RecyclerViewThis is what has been learned so far in relation to practical use,The specific practice also needs to be optimized and implemented in combination with its own project structure.
RecyclerViewis essential for development,Although its features and performance compare toListViewThere have been great improvements and enhancements,However, there are still some performance problems when used improperly,And there is still room for further optimization,结合mCacheViewExtension和DiffUtil的实现,让你的UI更加流畅.