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Android Kotlin-----RecyclerView的使用_android kotlin recyclerview

作者：码创造者 | 2024-07-04 15:28:04

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android kotlin recyclerview

程序中需要注意几点：

       MVC的设计模式、RecyclerView库的使用......

    

部分代码如下：

  首先在build.gradle(app)中添加RecyclerView库的依赖：

compile 'com.android.support:recyclerview-v7:26.1.0'

Model层：

    Category.kt 代码：

  1. class Category(val title:String,val image:String){
  2.     override fun toString(): String {
  3.         return title
  4.     }
  5. }//定义类型类

    Product.kt 代码：

class Product(val title:String,val price:String,val image:String)  //定义产品类

Control层：

   MainActivity.kt 代码：

  1. class MainActivity : AppCompatActivity() {
  2.  
  3.     //lateinit var adapter:CategoryAdapter
  4.     lateinit var adapter:CategoryRecycleAdapter
  5.     override fun onCreate(savedInstanceState: Bundle?) {
  6.         super.onCreate(savedInstanceState)
  7.         setContentView(R.layout.activity_main)
  8.  
  9.         //adapter= CategoryAdapter(this,DataService.categories)
  10.         //categoryListView.adapter=adapter
  11.  
  12.         //列表每一条的点击事件
  13.         adapter= CategoryRecycleAdapter(this,DataService.categories){
  14.             category ->
  15.             val productIntent=Intent(this,ProductActivity::class.java)
  16.             productIntent.putExtra(EXTRA_CATEGORY,category.title)
  17.             startActivity(productIntent)
  18.         }
  19.         categoryListView.adapter=adapter
  20.  
  21.         val layoutManager=LinearLayoutManager(this)
  22.         categoryListView.layoutManager=layoutManager
  23.         categoryListView.setHasFixedSize(true)
  24.     }
  25. }

   ProductActivity.kt 代码：

  1. class ProductActivity : AppCompatActivity() {
  2.     lateinit var adater:ProductAdapter
  3.     override fun onCreate(savedInstanceState: Bundle?) {
  4.         super.onCreate(savedInstanceState)
  5.         setContentView(R.layout.activity_product)
  6.  
  7.         val categroyType=intent.getStringExtra(EXTRA_CATEGORY)//传递值
  8.         Toast.makeText(this,"$categroyType",Toast.LENGTH_LONG).show()
  9.         adater=ProductAdapter(this,DataService.getProduct(categroyType))
  10.  
  11.         var spanCount=2
  12.         val screenSize=resources.configuration.screenWidthDp
  13.         if(screenSize >720){   //适应大的屏幕
  14.             spanCount=3
  15.         }
  16.  
  17.         val layoutManager=GridLayoutManager(this,2) //每行两列的网格布局
  18.         productsListView.layoutManager=layoutManager
  19.         productsListView.adapter=adater
  20.     }
  21. }

Adapter层：

   CategoryAdapter.kt(ListView的适配器，程序中被代替了，没有用到)

  1. class CategoryAdapter(val context: Context, val categories: List<Category>): BaseAdapter() {
  2.  
  3.     override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View {
  4.         val categoryView:View
  5.         val holder:ViewHolder
  6.  
  7.         if(convertView==null) {
  8.             //获取布局文件   显示布局变成默认包裹内容
  9.             categoryView = LayoutInflater.from(context).inflate(R.layout.category_list_item, null)
  10.             holder= ViewHolder()
  11.             holder.categoryImage = categoryView.findViewById(R.id.categoryImage)//获取id
  12.             holder.categoryName= categoryView.findViewById(R.id.categoryName)
  13.             categoryView.tag=holder     //tag:存储一些view的数据
  14.         }else{
  15.             //当convertView不为空的时候直接重新使用convertView从而减少了很多不必要的View的创建，然后加载数据
  16.             holder=convertView.tag as ViewHolder   //as:强制转换类型
  17.             categoryView=convertView
  18.         }
  19.         val category=categories[position]   //获取类别的位置
  20.         //获取资源文件中指定的图片    getIdentifier()方法可以方便的获各应用包下的指定资源ID
  21.         val resourceId=context.resources.getIdentifier(category.image,"drawable",context.packageName)
  22.         holder.categoryImage?.setImageResource(resourceId)
  23.  
  24.         holder.categoryName?.text=category.title    //获取标题
  25.         return categoryView
  26.     }
  27.  
  28.     override fun getItem(position: Int): Any {
  29.         return categories[position]
  30.     }
  31.  
  32.     override fun getItemId(position: Int): Long {
  33.         return 0
  34.     }
  35.  
  36.     override fun getCount(): Int {
  37.         return categories.count()
  38.     }
  39.     private class ViewHolder{
  40.         //不必每次加载都到布局文件中去拿View，提高了效率
  41.         var categoryImage:ImageView?=null
  42.         var categoryName:TextView?=null
  43.     }
  44. }

    CategoryRecycleAdapter.kt 代码：

  1. class CategoryRecycleAdapter(val context:Context,val categories:List<Category>,val itemClick:(Category) ->Unit) :RecyclerView.Adapter<CategoryRecycleAdapter.Holder>() {
  2.  
  3.     //onCreateViewHolder():是用来配合写好的ViewHolder来返回一个ViewHolder对象。这里也涉及到了条目布局的加载。
  4.     //viewType则表示需要给当前position生成的是哪一种ViewHolder，这个参数也说明了RecyclerView对多类型ItemView的支持。
  5.     override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): Holder {
  6.         val view=LayoutInflater.from(context).inflate(R.layout.category_list_item,parent,false)
  7.         return Holder(view,itemClick)
  8.     }
  9.  
  10.     override fun getItemCount(): Int {
  11.         return categories.count()
  12.     }
  13.  
  14.     //专门用来绑定ViewHolder里的控件和数据源中position位置的数据。
  15.     override fun onBindViewHolder(holder: Holder?, position: Int) {
  16.         holder?.bindCategory(categories[position],context)
  17.     }
  18.  
  19.      //定义内部类Holder
  20.     inner class Holder(itemView:View?,val itemClick:(Category) ->Unit): RecyclerView.ViewHolder(itemView){
  21.  
  22.         val categoryImage=itemView?.findViewById<ImageView>(R.id.categoryImage)
  23.         val categoryName=itemView?.findViewById<TextView>(R.id.categoryName)
  24.  
  25.         fun bindCategory(category: Category,context: Context){
  26.             val resourceId=context.resources.getIdentifier(category.image,"drawable",context.packageName)
  27.             categoryImage?.setImageResource(resourceId)
  28.             categoryName?.text=category.title
  29.             itemView.setOnClickListener { itemClick(category) }
  30.         }
  31.     }
  32. }

    ProductAdapter.kt 代码：

  1. class ProductAdapter(val context: Context,val products:List<Product>):RecyclerView.Adapter<ProductAdapter.ProductHolder>() {
  2.     override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): ProductHolder {
  3.         val view=LayoutInflater.from(context).inflate(R.layout.product_list_item,parent,false)
  4.         return ProductHolder(view)
  5.     }
  6.  
  7.     override fun getItemCount(): Int {
  8.         return products.count()
  9.     }
  10.  
  11.     override fun onBindViewHolder(holder: ProductHolder?, position: Int) {
  12.         holder?.bindProduct(products[position],context)
  13.     }
  14.  
  15.  
  16.     inner class ProductHolder(itemView:View?):RecyclerView.ViewHolder(itemView){
  17.  
  18.         val productImage=itemView?.findViewById<ImageView>(R.id.productImage)
  19.         val productName=itemView?.findViewById<TextView>(R.id.categoryName)
  20.         val productPrice=itemView?.findViewById<TextView>(R.id.productPrice)
  21.  
  22.         fun bindProduct(products: Product,context: Context){
  23.             val resourcesProductId=context.resources.getIdentifier(products.image,"drawable",context.packageName)
  24.             productImage?.setImageResource(resourcesProductId)
  25.             productName?.text=products.title
  26.             productPrice?.text=products.price
  27.         }
  28.     }
  29. }

Services层：

    DataService.kt 代码：

  1. object DataService {
  2.     val categories= listOf(
  3.             Category("衬衫","shirtimage"),
  4.             Category("卫衣","hoodieimage"),
  5.             Category("帽子","hatimage"),
  6.             Category("数码产品","digitalgoodsimage"),
  7.             Category("衬衫","shirtimage"),
  8.             Category("卫衣","hoodieimage"),
  9.             Category("帽子","hatimage"),
  10.             Category("数码产品","digitalgoodsimage"),
  11.             Category("衬衫","shirtimage"),
  12.             Category("卫衣","hoodieimage"),
  13.             Category("帽子","hatimage"),
  14.             Category("数码产品","digitalgoodsimage")
  15.     )
  16.  
  17.     val hats= listOf(
  18.             Product("Devslopes Graphic Beanie","$18","hat1"),
  19.             Product("Devslopes Hat Black","$20","hat2"),
  20.             Product("Devslopes Hat White","$18","hat3"),
  21.             Product("Devslopes Hat Snapback","$22","hat4"),
  22.             Product("Devslopes Graphic Beanie","$18","hat1"),
  23.             Product("Devslopes Hat Black","$20","hat2"),
  24.             Product("Devslopes Hat White","$18","hat3"),
  25.             Product("Devslopes Hat Snapback","$22","hat4"),
  26.             Product("Devslopes Graphic Beanie","$18","hat1"),
  27.             Product("Devslopes Hat Black","$20","hat2"),
  28.             Product("Devslopes Hat White","$18","hat3"),
  29.             Product("Devslopes Hat Snapback","$22","hat4"),
  30.             Product("Devslopes Graphic Beanie","$18","hat1"),
  31.             Product("Devslopes Hat Black","$20","hat2"),
  32.             Product("Devslopes Hat White","$18","hat3"),
  33.             Product("Devslopes Hat Snapback","$22","hat4")
  34.     )
  35.  
  36.     val hoodies= listOf(
  37.             Product("Devslopes Hoodie Gray","$28","hoodie1"),
  38.             Product("Devslopes Hoodie Red","$32","hoodie2"),
  39.             Product("Devslopes Gray Hoodie","$28","hoodie3"),
  40.             Product("Devslopes Black Hoodie","$32","hoodie4"),
  41.             Product("Devslopes Hoodie Gray","$28","hoodie1"),
  42.             Product("Devslopes Hoodie Red","$32","hoodie2"),
  43.             Product("Devslopes Gray Hoodie","$28","hoodie3"),
  44.             Product("Devslopes Black Hoodie","$32","hoodie4"),
  45.             Product("Devslopes Hoodie Gray","$28","hoodie1"),
  46.             Product("Devslopes Hoodie Red","$32","hoodie2"),
  47.             Product("Devslopes Gray Hoodie","$28","hoodie3"),
  48.             Product("Devslopes Black Hoodie","$32","hoodie4"),
  49.             Product("Devslopes Hoodie Gray","$28","hoodie1"),
  50.             Product("Devslopes Hoodie Red","$32","hoodie2"),
  51.             Product("Devslopes Gray Hoodie","$28","hoodie3"),
  52.             Product("Devslopes Black Hoodie","$32","hoodie4"),
  53.             Product("Devslopes Hoodie Gray","$28","hoodie1"),
  54.             Product("Devslopes Hoodie Red","$32","hoodie2"),
  55.             Product("Devslopes Gray Hoodie","$28","hoodie3"),
  56.             Product("Devslopes Black Hoodie","$32","hoodie4"),
  57.             Product("Devslopes Hoodie Gray","$28","hoodie1"),
  58.             Product("Devslopes Hoodie Red","$32","hoodie2"),
  59.             Product("Devslopes Gray Hoodie","$28","hoodie3"),
  60.             Product("Devslopes Black Hoodie","$32","hoodie4")
  61.     )
  62.  
  63.     val shirts= listOf(
  64.             Product("Devslopes Shirt Black","$18","shirt1"),
  65.             Product("Devslopes Badge Light Gray","$20","shirt2"),
  66.             Product("Devslopes Logo Shirt Red","$22","shirt3"),
  67.             Product("Devslopes Hustle","$22","shirt4"),
  68.             Product("Kickflip","$18","shirt5"),
  69.             Product("Devslopes Shirt Black","$18","shirt1"),
  70.             Product("Devslopes Badge Light Gray","$20","shirt2"),
  71.             Product("Devslopes Logo Shirt Red","$22","shirt3"),
  72.             Product("Devslopes Hustle","$22","shirt4"),
  73.             Product("Kickflip","$18","shirt5"),
  74.             Product("Devslopes Shirt Black","$18","shirt1"),
  75.             Product("Devslopes Badge Light Gray","$20","shirt2"),
  76.             Product("Devslopes Logo Shirt Red","$22","shirt3"),
  77.             Product("Devslopes Hustle","$22","shirt4"),
  78.             Product("Kickflip","$18","shirt5"),
  79.             Product("Devslopes Shirt Black","$18","shirt1"),
  80.             Product("Devslopes Badge Light Gray","$20","shirt2"),
  81.             Product("Devslopes Logo Shirt Red","$22","shirt3"),
  82.             Product("Devslopes Hustle","$22","shirt4"),
  83.             Product("Kickflip","$18","shirt5")
  84.     )
  85.  
  86.     val digitalGood= listOf<Product>()   //空的数码产品
  87.     fun getProduct(category:String):List<Product>{       //根据类型获取商品
  88.         return when(category){
  89.             "衬衫"-> shirts
  90.             "帽子"-> hats
  91.             "卫衣"-> hoodies
  92.             else -> digitalGood
  93.         }
  94.     }}

Utility层：

    Contents.kt  代码：

const val EXTRA_CATEGORY="category"

View层：

    activity_main.xml 代码：

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     tools:context="com.example.dpl.coderswag.Controller.MainActivity">
  8.  
  9.     <TextView
  10.         android:id="@+id/textView"
  11.         android:layout_width="wrap_content"
  12.         android:layout_height="wrap_content"
  13.         android:layout_marginStart="16dp"
  14.         android:layout_marginTop="16dp"
  15.         android:text="种类"
  16.         android:textSize="18sp"
  17.         app:layout_constraintStart_toStartOf="parent"
  18.         app:layout_constraintTop_toTopOf="parent" />
  19.  
  20.     <android.support.v7.widget.RecyclerView
  21.         android:id="@+id/categoryListView"
  22.         android:layout_width="0dp"
  23.         android:layout_height="0dp"
  24.         android:layout_marginTop="16dp"
  25.         android:divider="@null"
  26.         app:layout_constraintBottom_toBottomOf="parent"
  27.         app:layout_constraintEnd_toEndOf="parent"
  28.         app:layout_constraintHorizontal_bias="0.0"
  29.         app:layout_constraintStart_toStartOf="parent"
  30.         app:layout_constraintTop_toBottomOf="@+id/textView"
  31.         app:layout_constraintVertical_bias="1.0" />
  32.  
  33. </android.support.constraint.ConstraintLayout>

activity_product.xml 代码：

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:app="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     android:layout_width="match_parent"
  6.     android:layout_height="match_parent"
  7.     android:background="@android:color/white"
  8.     tools:context="com.example.dpl.coderswag.Controller.ProductActivity">
  9.  
  10.     <TextView
  11.         android:id="@+id/textView"
  12.         android:layout_width="wrap_content"
  13.         android:layout_height="wrap_content"
  14.         android:layout_marginStart="16dp"
  15.         android:layout_marginTop="16dp"
  16.         android:text="产品"
  17.         android:textSize="18sp"
  18.         app:layout_constraintStart_toStartOf="parent"
  19.         app:layout_constraintTop_toTopOf="parent" />
  20.  
  21.     <android.support.v7.widget.RecyclerView
  22.         android:id="@+id/productsListView"
  23.         android:layout_width="0dp"
  24.         android:layout_height="0dp"
  25.         android:layout_marginTop="16dp"
  26.         android:divider="@null"
  27.         app:layout_constraintBottom_toBottomOf="parent"
  28.         app:layout_constraintEnd_toEndOf="parent"
  29.         app:layout_constraintHorizontal_bias="0.0"
  30.         app:layout_constraintStart_toStartOf="parent"
  31.         app:layout_constraintTop_toBottomOf="@+id/textView"
  32.         app:layout_constraintVertical_bias="1.0" />
  33.  
  34. </android.support.constraint.ConstraintLayout>

category_list_item.xml 代码：

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <android.support.constraint.ConstraintLayout
  3.     xmlns:android="http://schemas.android.com/apk/res/android"
  4.     xmlns:app="http://schemas.android.com/apk/res-auto"
  5.     xmlns:tools="http://schemas.android.com/tools"
  6.     android:layout_width="match_parent"
  7.     android:layout_height="166dp">
  8.  
  9.     <ImageView
  10.         android:id="@+id/categoryImage"
  11.         android:layout_width="0dp"
  12.         android:layout_height="150dp"
  13.         android:layout_marginBottom="8dp"
  14.         android:layout_marginTop="8dp"
  15.         android:scaleType="centerCrop"
  16.         app:layout_constraintBottom_toBottomOf="parent"
  17.         app:layout_constraintEnd_toEndOf="parent"
  18.         app:layout_constraintStart_toStartOf="parent"
  19.         app:layout_constraintTop_toTopOf="parent"
  20.         tools:srcCompat="@drawable/hatimage" />
  21.  
  22.     <TextView
  23.         android:id="@+id/categoryName"
  24.         android:layout_width="wrap_content"
  25.         android:layout_height="wrap_content"
  26.         android:layout_marginBottom="8dp"
  27.         android:layout_marginEnd="8dp"
  28.         android:layout_marginStart="8dp"
  29.         android:layout_marginTop="8dp"
  30.         android:text="HATS"
  31.         android:textColor="@android:color/white"
  32.         android:textSize="24sp"
  33.         android:textStyle="bold"
  34.         app:layout_constraintBottom_toBottomOf="@+id/categoryImage"
  35.         app:layout_constraintEnd_toEndOf="parent"
  36.         app:layout_constraintStart_toStartOf="parent"
  37.         app:layout_constraintTop_toTopOf="parent" />
  38. </android.support.constraint.ConstraintLayout>

product_list_item.xml 代码：

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <android.support.constraint.ConstraintLayout
  3.     xmlns:android="http://schemas.android.com/apk/res/android"
  4.     xmlns:app="http://schemas.android.com/apk/res-auto"
  5.     xmlns:tools="http://schemas.android.com/tools"
  6.     android:layout_width="match_parent"
  7.     android:layout_height="wrap_content">
  8.  
  9.     <ImageView
  10.         android:id="@+id/productImage"
  11.         android:layout_width="0dp"
  12.         android:layout_height="0dp"
  13.         android:layout_marginEnd="8dp"
  14.         android:layout_marginStart="8dp"
  15.         android:layout_marginTop="8dp"
  16.         app:layout_constraintDimensionRatio="w,1:1"
  17.         app:layout_constraintEnd_toEndOf="parent"
  18.         app:layout_constraintStart_toStartOf="parent"
  19.         app:layout_constraintTop_toTopOf="parent"
  20.         app:srcCompat="@drawable/hat1" />
  21.  
  22.     <TextView
  23.         android:id="@+id/productName"
  24.         android:layout_width="0dp"
  25.         android:layout_height="wrap_content"
  26.         android:layout_marginEnd="16dp"
  27.         android:layout_marginStart="16dp"
  28.         android:layout_marginTop="8dp"
  29.         android:textAlignment="center"
  30.         android:textSize="18sp"
  31.         app:layout_constraintEnd_toEndOf="parent"
  32.         app:layout_constraintStart_toStartOf="parent"
  33.         app:layout_constraintTop_toBottomOf="@+id/productImage"
  34.         tools:text="帽子A" />
  35.  
  36.     <TextView
  37.         android:id="@+id/productPrice"
  38.         android:layout_width="wrap_content"
  39.         android:layout_height="wrap_content"
  40.         android:layout_marginBottom="8dp"
  41.         android:layout_marginEnd="8dp"
  42.         android:layout_marginStart="8dp"
  43.         android:layout_marginTop="8dp"
  44.         android:textSize="14sp"
  45.         app:layout_constraintBottom_toBottomOf="parent"
  46.         app:layout_constraintEnd_toEndOf="parent"
  47.         app:layout_constraintStart_toStartOf="parent"
  48.         app:layout_constraintTop_toBottomOf="@+id/productName"
  49.         tools:text="￥30" />
  50. </android.support.constraint.ConstraintLayout>

运行效果：



程序源码： https://github.com/dpl12/CoderSwag


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