Android RecyclerView：什么是，通过简单示例学习

var arr1 = [1,2,3] //imagine a simple View as an Array
//we can imagine this as a NumberTextView which doesn't really exist
//but we could imagine there's one that makes it easy to use numbers
var arr2 = ["a","b","c"] // We can imagine this as another simple view

var nestedArr = [arr1,arr2] //in our analogy, we can now group views
//together and the structure that would hold that would be what we call the ViewGroup

class AmericanCharger() {
    var chargingPower = 10
}
class BritishCharger(){
    var chargingPower = 5
}

class AmericanDevice()
class BritishDevice()

var myAmericanPhone = new AmericanDevice()
var myBritishPhone = new BritishDevice()

sealed trait Device
class AmericanDevice : Device{
    fun charge(charger:AmericanCharger){
        //Do some American charging
    }
}
class BritishDevice: Device{
    fun charge(charger:BritishCharger){
        //Do some British charging
    }
}

class AmericanToBritishChargerAdapter(theAmericanCharger:AmericanCharger){
    fun returnNewCharger(): BritishCharger{
            //convert the American charger to a BritishCharger
            //we would change the American charging functionality
            //to British charging functionality to make sure the
            //adapter doesn't destroy the device. The adapter could
            //, for example, control the power output by dividing by 2
            //our adapter could encompass this functionality in here

           var chargingPower:Int = theAmericanCharger.chargingPower / 2
           var newBritishCharger = new BritishCharger()
           newBritishCharger.chargingPower = theAmericanCharger.chargingPower/2

        return newBritishCharger
    }
}

var myBritishDevice = new BritishDevice()
var americanChargerIFound = new AmericanCharger()

var myBritishDevice = new BritishDevice()
var americanChargerIFound = new AmericanCharger()
myBritishDevice.charge(americanChargerIFound)

var myBritishDevice = new BritishDevice()
var americanChargerIFound = new AmericanCharger()
//We create the adapter and feed it the americanCharger
var myAdapter =  AmericanToBritishChargerAdapter(americanChargerIFound)
//calling returnNewCharger from myAdapter would return a BritishCharger
var britishChargerFromAdapter = myAdapter.returnNewCharger()
//and once we have the britishCharger we can now use it
myBritishDevice.charge(britishChargerFromAdapter)

//OneContactView
<OneContact>
<TextView>{{PlaceHolderForName}}</TextView>
<TextView>{{PlaceHolderForAddress}}</TextView>
<ImageView>{{PlaceHolderForProfilePicture}}</ImageView>
<TextView>{{PlaceHolderForPhoneNumber}}</TextView>
</OneContact>

<ContactList>
</ContactList>

data  class Contact(var name:String, var address:String, var pic:String, var phoneNumber:Int)

var contact1 = Contact("Guru","Guru97", "SomePic1.jpg", 991)
var contact2 = Contact("Guru","Guru98", "SomePic2.jpg", 992)
var contact3 = Contact("Guru","Guru99", "SomePic3.jpg", 993)

var myContacts:ArrayList<Contact> = arrayListOf<Contact>(contact1,contact2,contact3)

fun createViewHolder(@NonNull parent: ViewGroup, viewType: Int): ViewHolder

sealed trait Animal{
    fun sound():String
}

data class Cat(name:String):Animal{
    fun sound(){
        "Meow"
        }
}
data class Dog(name:String):Animal{
    fun sound(){
        "Woof"
        }
}

var cat1 = Cat("Tubby")
var dog1 = Dog("Scooby")
cat1.sound() //meow
dog1.sound() //woof

class SpeechPoweredAnimalByWrapper(var myAnimal:Animal){

    fun sound(){
        myAnimal.sound()
    }

    fun speak(){
        println("Hello, my name is ${myAnimal.name}")
    }
}

var cat1 =  Cat("Garfield")
cat1.sound()//"meow"
cat1.speak()// doesn't work as it isn't implemented
var talkingCat = new SpeechPoweredAnimalByWrapper(cat1)
talkingCat.sound() //"meow" the sound method calls the one defined for cat1
talkingCat.speak() //"Hello, my name is Garfield"

abstract class SpeechPowered(var myAnimal:Animal){

    fun sound(){
        myAnimal.sound()
    }

    fun speak(){
        println("Hello, my name is ${myAnimal.name}")
    }
}

class SpeechPoweredAnimal(var myAnimal:Animal):SpeechPowered(myAnimal)

var cat1 =  Cat("Tubby")
var speakingKitty = SpeechPoweredAnimal(cat1)
speakingKitty.speak() //"Hello, my name is Tubby"

//The View argument we pass is converted to a ViewHolder which uses the View to give it more abilities and in turn work with the RecyclerView
class OneContactViewHolder(ourContactView: View) : RecyclerView.ViewHolder(ourContactView)

contactList:Array<Contact>

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.guru99.learnrecycler"
        minSdkVersion 17
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'),
             'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.core:core-ktx:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

    implementation "androidx.recyclerview:recyclerview:1.1.0"
}

package com.guru99.learnrecycler

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle

class MainActivity : AppCompatActivity() {

    var fruitNames:Array<String> = arrayOf<String>("Banana", "Mango", "Passion fruit", "Orange", "Grape")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
}

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/fruitName"
    />
</TextView>

<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView 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:id="@+id/fruitRecyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" />

android:id="@+id/fruitRecyclerView"

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    var myFruitRecyclerView: RecyclerView = findViewById(R.id.fruitRecyclerView)
}

package com.guru99.learnrecycler

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.recyclerview.widget.RecyclerView

class MainActivity : AppCompatActivity() {

    var fruitNames:Array<String> = arrayOf<String>("Banana", "Mango", "Passion fruit", "Orange", "Grape")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        var myFruitRecyclerView: RecyclerView = findViewById(R.id.fruitRecyclerView)
    }

    class FruitViewHolder(fruitView: View): RecyclerView.ViewHolder(fruitView)

}

package com.guru99.learnrecycler

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.recyclerview.widget.RecyclerView

class MainActivity : AppCompatActivity() {

    var fruitNames:Array<String> = arrayOf<String>("Banana", "Mango", "Passion fruit", "Orange", "Grape")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        var myFruitRecyclerView: RecyclerView = findViewById(R.id.fruitRecyclerView)
    }

    class FruitViewHolder(fruitView: View): RecyclerView.ViewHolder(fruitView)

    class FruitArrayAdapter(var fruitArray: Array<String>) : RecyclerView.Adapter<FruitViewHolder>()
}

class FruitListAdapter(var fruitArray: Array<String>) : RecyclerView.Adapter<FruitViewHolder>() {
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FruitViewHolder {

     }

     override fun getItemCount(): Int {

     }

     override fun onBindViewHolder(holder: FruitViewHolder, position: Int) {

     }
 }

class FruitListAdapter(var fruitArray: Array<String>) : RecyclerView.Adapter<FruitViewHolder>() {
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FruitViewHolder {

        }

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

        override fun onBindViewHolder(holder: FruitViewHolder, position: Int) {

        }
    }

class FruitViewHolder(fruitView: View): RecyclerView.ViewHolder(fruitView)

class FruitListAdapter(var fruitArray: Array<String>) : RecyclerView.Adapter<FruitViewHolder>() {

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FruitViewHolder {

            var fruitView = LayoutInflater.from(parent.context).inflate(R.layout.one_fruit_view, parent, false)

            var fruitViewHolder = FruitViewHolder(fruitView)

            return fruitViewHolder

        }

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

        override fun onBindViewHolder(holder: FruitViewHolder, position: Int) {

        }
    }

fun onBindViewHolder(holder: FruitViewHolder, position: Int)

override fun onBindViewHolder(holder: FruitViewHolder, position: Int) {

          var ourFruitTextView = holder.itemView.findViewById<TextView>(R.id.fruitName)

          var aFruitName = fruitArray.get(position)

          ourFruitTextView.setText(aFruitName)
      }

class FruitListAdapter(var fruitArray: Array<String>) : RecyclerView.Adapter<FruitViewHolder>() {

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FruitViewHolder {

            var fruitView = LayoutInflater.from(parent.context).inflate(R.layout.one_fruit_view, parent, false)

            var fruitViewHolder = FruitViewHolder(fruitView)

            return fruitViewHolder
        }

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

        override fun onBindViewHolder(holder: FruitViewHolder, position: Int) {

            var ourFruitTextView = holder.itemView.findViewById<TextView>(R.id.fruitName)

            var aFruitName = fruitArray.get(position)

            ourFruitTextView.setText(aFruitName)
        }
    }

override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)

       var myFruitRecyclerView: RecyclerView = findViewById(R.id.fruitRecyclerView)

       var fruitLinearLayout = LinearLayoutManager(this)

       myFruitRecyclerView.layoutManager =fruitLinearLayout

   }

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        var myFruitRecyclerView: RecyclerView = findViewById(R.id.fruitRecyclerView)

        var fruitLinearLayout = LinearLayoutManager(this)

        myFruitRecyclerView.layoutManager =fruitLinearLayout

        var fruitListAdapter = FruitListAdapter(fruitNames)

        myFruitRecyclerView.adapter =fruitListAdapter
    }

package com.guru99.learnrecycler

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

class MainActivity : AppCompatActivity() {

    var fruitNames:Array<String> = arrayOf<String>("Banana", "Mango", "Passion fruit", "Orange", "Grape")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        var myFruitRecyclerView: RecyclerView = findViewById(R.id.fruitRecyclerView)

        var fruitLinearLayout = LinearLayoutManager(this)

        myFruitRecyclerView.layoutManager =fruitLinearLayout

        var fruitListAdapter = FruitListAdapter(fruitNames)

        myFruitRecyclerView.adapter =fruitListAdapter
    }

    class FruitViewHolder(fruitView: View): RecyclerView.ViewHolder(fruitView)

    class FruitListAdapter(var fruitArray: Array<String>) : RecyclerView.Adapter<FruitViewHolder>() {

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FruitViewHolder {

            var fruitView = LayoutInflater.from(parent.context).inflate(R.layout.one_fruit_view, parent, false)

            var fruitViewHolder = FruitViewHolder(fruitView)

            return fruitViewHolder
        }

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

        override fun onBindViewHolder(holder: FruitViewHolder, position: Int) {

            var ourFruitTextView = holder.itemView.findViewById<TextView>(R.id.fruitName)

            var aFruitName = fruitArray.get(position)

            ourFruitTextView.setText(aFruitName)
        }
    }
}