RecyclerView(GridLayout)

1. Gradle

implementation 'com.android.support:recyclerview-v7:28.0.0'

저 뒤에 숫자는 자기꺼랑 버전을 맞춰준다.

2. Layout

 RecyclerView랑 안에 들어갈 layout하나씩 만들어준다.

3. Adaptor

class MainRecyclerViewAdaptor: RecyclerView.Adapter<RecyclerView.ViewHolder>(){

    //각각의 아이템의 디자인레이아웃을 불러온다
    override fun onCreateViewHolder(p0: ViewGroup, p1: Int): RecyclerView.ViewHolder {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }

    //아이템의 개수를 카운트한다
    override fun getItemCount(): Int {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }

    //각각의 아이템의 데이터를 바인딩 시켜준다
    override fun onBindViewHolder(p0: RecyclerView.ViewHolder, p1: Int) {
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    }
}

기본형태. RecyclerView.Adapter<RecyclerView.ViewHolder>() <- 요것을 상속한다.

package com.example.lipnus.lipnus_example

import android.os.Bundle
import android.support.constraint.R.id.parent
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.GridLayoutManager
import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.ViewGroup
import android.view.View
import android.widget.GridLayout
import android.widget.ImageView
import kotlinx.android.synthetic.main.activity_main.*


class MainActivity : AppCompatActivity() {

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

        lipnus_recyclerView.adapter = MainRecyclerViewAdaptor()
        var gridManager = GridLayoutManager(this, 3)
        lipnus_recyclerView.layoutManager = gridManager

        gridManager.spanSizeLookup = object : GridLayoutManager.SpanSizeLookup(){
            override fun getSpanSize(position: Int): Int {
                if(position==0){
                    return 3 //3칸 차지
                }
                return 1 //1칸 차지
            }

        }
    }


    class MainRecyclerViewAdaptor: RecyclerView.Adapter<RecyclerView.ViewHolder>(){

        var images = arrayOf(R.drawable.s1, R.drawable.s2, R.drawable.s3, R.drawable.s4)


        //포지션 값에 따라서 타입을 바꿔준다
        override fun getItemViewType(position: Int): Int {
            if(position==0) return 0
            return 1

            //리턴값은 onCreateViewHolder의 viewType매개변수로 들어간다
        }


        //각각의 아이템의 디자인레이아웃을 불러온다
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
            var view = LayoutInflater.from(parent!!.context).inflate(R.layout.item_layout, parent, false)

            var params = view.layoutParams

            if(viewType==0){
                params.height = parent.measuredWidth
                params.width = parent.measuredWidth
            }else{
                //인스타처럼 3칸짜리 정사각형 만들기
                params.height = parent.measuredWidth/3
                params.width = parent.measuredWidth/3
                view.layoutParams = params
            }

            return CustomViewHolder(view)
        }



        class CustomViewHolder(view: View) : RecyclerView.ViewHolder(view) {

            var imageview: ImageView? = null;
            init {
                imageview = view!!.findViewById(R.id.LayoutItem_imageview)
            }

        }

        //아이템의 개수를 카운트한다
        override fun getItemCount(): Int {
            return images.size
        }

        //각각의 아이템에 데이터를 바인딩시켜준다
        override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
            var view = holder as CustomViewHolder
            view!!.imageview!!.setImageResource(images[position])

        }

    }
}