# Recycler View 基礎用法- kotlin

1. OnePieceAdapter.kt
* Adtapter類別定義參數onePieceList他的資料型態是List,而List<>裡面的OnePiece是我們定義的data class,
* 繼承RecyclerView.Adapter, 而<>裡面OnePieceAdapter.ViewHolder是我們要額外再定義的一個class

@Suppress("UNREACHABLE_CODE")
class OnePieceAdapter(val onePieceList: List<OnePiece>) : RecyclerView.Adapter<OnePieceAdapter.ViewHolder>(){

    init {
        Log.d("類別初始化", "init執行了")
    }
    inner class ViewHolder(view: View) : RecyclerView.ViewHolder(view){
        //viewHolder定義要顯示在recyclerView的layout元件
        val fruitImage = view.findViewById<ImageView>(R.id.fruitImage)
        val fruitName = view.findViewById<TextView>(R.id.fruitName)
        
        //定義真正綁定的工作
        fun bindData(data: OnePiece){
            fruitImage.setImageResource(data.imageId)
            fruitName.text = data.name
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        //把要顯示在recyclerView的view inflate出來, fruit_item是要綁進Adapter的xml.
        Log.d("onCreateViewHolder", "onCreateViewHolder準備執行")
        val view = LayoutInflater.from(parent.context).inflate(R.layout.fruit_item, parent, false)
        Log.d("return", "onCreateViewHolder生成view")
        return ViewHolder(view)
    }

    override fun getItemCount(): Int {
        Log.d("getItemCount", "取得要綁給Adapter的資料大小")
        return onePieceList.size
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        Log.d("顯示資料", "Bind資料到recycler View")
        val fruit = onePieceList[position]
        //將要綁定的位置與data 透過ViewHolder的涵式進行操作
        holder.bindData(fruit)
    }
}

2. OnePiece.kt
* 這邊定義data class :OnePiece ,要傳給Adapter的資料型態

data class OnePiece(val name: String, val imageId: Int)

3. MainActivity.kt
*

class MainActivity : AppCompatActivity() {
    //定義要綁定給Adapter的資料
    private val fruitList = ArrayList<OnePiece>()
    
    lateinit var recyclerView : RecyclerView
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        recyclerView = findViewById(R.id.recyclerView)
        //要綁定給Adapter的數據先初始化塞進List
        initFruits()
        //布局Layout Manager :瀑布流
//        val layoutManager = StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL)
//        recyclerView.layoutManager = layoutManager
        //線性流
        val linearLayoutManager = LinearLayoutManager(this)
        recyclerView.layoutManager = linearLayoutManager

        //自訂分隔線(自定義圖片)
        //var divider = DividerItemDecoration(this, DividerItemDecoration.VERTICAL)
       // ContextCompat.getDrawable(this, R.drawable.ic_launcher_foreground)?.let { divider.setDrawable(it) }
        //recyclerView.addItemDecoration(divider)
        //使用內建的分隔線↓
        recyclerView.addItemDecoration(DividerItemDecoration(this@MainActivity,LinearLayoutManager.VERTICAL))

        //綁定Adapter
        val adapter = OnePieceAdapter(fruitList)
        recyclerView.adapter = adapter
    }

    //自定義要給Adapter的資料
    private fun initFruits() {
        repeat(2) {
            fruitList.add(OnePiece("魯夫", R.drawable.luffy))
            fruitList.add(OnePiece("布魯克",R.drawable.brook))
            fruitList.add(OnePiece("喬巴", R.drawable.chopper))
            fruitList.add(OnePiece("佛朗基",R.drawable.frank))
            fruitList.add(OnePiece("基拉",R.drawable.killer))
            fruitList.add(OnePiece("娜美", R.drawable.nami))
            fruitList.add(OnePiece("羅賓", R.drawable.robin))
            fruitList.add(OnePiece("香吉", R.drawable.sanji))
            fruitList.add(OnePiece("烏索普", R.drawable.sogeking))
            fruitList.add(OnePiece("德瑞克", R.drawable.xdrike))
            fruitList.add(OnePiece("拖拉法爾加-羅", R.drawable.trafalg))
            fruitList.add(OnePiece("儸儸諾亞-索隆", R.drawable.zoro))
        }
    }
}

[recyclerview的機制](https://www.jianshu.com/p/21a1384df9a1)

###### tags: `recycler view` `kotlin` `Android`