# 1. 前言 这里记录一下这里使用`RecyclerView`的过程。 # 2. 使用 首先定义好对应子项的`xml`布局文件，这里命名为`choose_item_layout.xml`： ~~~ <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" tools:ignore="RtlSymmetry" android:layout_width="wrap_content" android:layout_height="50dp" android:background="@drawable/choose_item_border_radius" android:orientation="horizontal" android:paddingEnd="10dp"> <RelativeLayout tools:ignore="UselessParent" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center_vertical" android:padding="10dp"> <RadioButton android:id="@+id/choose_category_page_item_rb" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerVertical="true"/> <ImageView android:id="@+id/choose_category_page_item_iv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerVertical="true" android:layout_toEndOf="@id/choose_category_page_item_rb" android:src="@drawable/tab_me" /> <TextView android:id="@+id/choose_category_page_item_tv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerVertical="true" android:layout_marginStart="10dp" android:layout_toEndOf="@id/choose_category_page_item_iv" android:gravity="center" android:text="@string/title" android:textColor="@color/black" android:textSize="18sp"/> </RelativeLayout> </LinearLayout> ~~~ 也就是：  然后，在主布局文件中加入`RecyclerView`，即： ~~~ <androidx.recyclerview.widget.RecyclerView android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/choose_category_page_rv" > </androidx.recyclerview.widget.RecyclerView> ~~~ 然后为这个`RecyclerView`创建适配器： ~~~ class ChooseCategoryPageRVAdapter(context: Context, datas: MutableList<ChooseCategoryItemBean>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() { // 列表项数据 var mItems: MutableList<ChooseCategoryItemBean> = datas var mCtx: Context? = context override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder { // 实例化item val inflateView = LayoutInflater.from(mCtx).inflate(R.layout.choose_item_layout, parent, false) return MyViewHolder(inflateView) } override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) { // 设置数据 val itemView = holder as MyViewHolder val itemData = mItems.get(position) itemView.radioButton.isChecked = itemData.isChoose itemView.imageView.setImageResource(itemData.img) itemView.textView.text = itemData.text } override fun getItemCount(): Int { return mItems.size } class MyViewHolder(itemView: View): RecyclerView.ViewHolder(itemView) { var radioButton: RadioButton = itemView.findViewById(R.id.choose_category_page_item_rb) var imageView: ImageView = itemView.findViewById(R.id.choose_category_page_item_iv) var textView: TextView = itemView.findViewById(R.id.choose_category_page_item_tv) } } ~~~ 当然，对应的`ChooseCategoryItemBean`： ~~~ data class ChooseCategoryItemBean( var img: Int, var text: String, var isChoose: Boolean ) ~~~ 因为这里我需要将数据存储在用户本地数据库中，所以这里需要查询数据库，至于`Room`框架的使用，这里不再介绍。直接给出使用部分： ~~~ class ChooseCategoryActivity : AppCompatActivity() { // 找到这个RV val choose_category_page_rv by lazy { findViewById<RecyclerView>(R.id.choose_category_page_rv) } var chooseCategoryPageRVAdapter: ChooseCategoryPageRVAdapter? = null val chooseCategoryItemDao: ChooseCategoryItemDao? by lazy { MFNoteDataBase.getInstance(this)?.chooseCategoryItemDao() } override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_choose_category) // 设置数据 setDataToRecyclerView() } fun setDataToRecyclerView() { // 指定为网格布局，每行放三个 val gridLayoutManager = GridLayoutManager(applicationContext, 2) // 设置布局管理器 choose_category_page_rv.layoutManager = gridLayoutManager; // 设置分割线，即间距 choose_category_page_rv.addItemDecoration(object : RecyclerView.ItemDecoration() { override fun getItemOffsets( outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State ) { super.getItemOffsets(outRect, view, parent, state) // 设置left/top/right/bottom的间距 outRect.set(10, 10, 10, 10) } }) // 加载数据 val datas: List<ChooseCategoryItemBean>? = loadItemData() chooseCategoryPageRVAdapter = ChooseCategoryPageRVAdapter(this, datas ?: initializationChooseCategoryItemData()); choose_category_page_rv.setAdapter(chooseCategoryPageRVAdapter); } fun loadItemData(): List<ChooseCategoryItemBean>? { chooseCategoryItemDao?.apply { return getAllChooseCategoryItem() } return null } fun initializationChooseCategoryItemData(): List<ChooseCategoryItemBean> { val bean1 = ChooseCategoryItemBean(0, R.drawable.ic_baseline_work_24, "工作", false) val bean5 = ChooseCategoryItemBean(4, R.drawable.ic_baseline_brush_24, "学习", false) val bean2 = ChooseCategoryItemBean(1, R.drawable.ic_baseline_add_shopping_cart_24, "购物", false) val bean3 = ChooseCategoryItemBean(2, R.drawable.ic_baseline_camera_roll_24, "旅游", false) val bean4 = ChooseCategoryItemBean(3, R.drawable.ic_baseline_attach_file_24, "收藏", false) val bean6 = ChooseCategoryItemBean(5, R.drawable.ic_baseline_directions_run_24, "运动", false) val items = listOf(bean1, bean5, bean2, bean3, bean4, bean6) // 存储到数据库 storageDefaultCategoryItems(items) return items } // 存储默认的分类到数据库 fun storageDefaultCategoryItems(items: List<ChooseCategoryItemBean>){ for(item in items){ chooseCategoryItemDao?.insertDefault(item) } } } ~~~ 效果：