วิธีเพิ่ม Divider และ Spacing ระหว่าง Item ใน RecyclerView

ตัวอย่างนี้สาธิตวิธี เพิ่ม Divider และ Spacing ระหว่าง Item ใน RecyclerView

ขั้นตอนที่ 1: สร้างโปรเจกต์ใหม่ใน Android Studio

ไปที่ File → New Project และกรอกรายละเอียดที่จำเป็นทั้งหมด

ขั้นตอนที่ 2: เพิ่มโค้ดใน res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto">
    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <android.support.v7.widget.Toolbar
            android:id="@+id/appbarlayout_tool_bar"
            android:background="@color/colorPrimary"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_scrollFlags="scroll|snap|enterAlways"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
    </android.support.design.widget.AppBarLayout>
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>
</android.support.design.widget.CoordinatorLayout>

ขั้นตอนที่ 3: เพิ่มโค้ดใน src/MainActivity.java

package com.example.myapplication;

import android.annotation.TargetApi;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    TextView text;
    ArrayList<String> list = new ArrayList<>();
    private RecyclerView recyclerView;
    private CustomAdapter mAdapter;
    private OnClickInterface onClickInterface;

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = findViewById(R.id.appbarlayout_tool_bar);
        toolbar.setTitle("This is toolbar.");
        setSupportActionBar(toolbar);

        onClickInterface = new OnClickInterface() {
            @Override
            public void setClick(int abc) {
                list.remove(abc);
                Toast.makeText(MainActivity.this, "Position is " + abc, Toast.LENGTH_LONG).show();
                mAdapter.notifyDataSetChanged();
            }
        };

        recyclerView = findViewById(R.id.recycler_view);
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        mAdapter = new CustomAdapter(this, list, onClickInterface);
        recyclerView.setAdapter(mAdapter);

        // เพิ่ม Divider ด้วย DividerItemDecoration (Built-in)
        DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(
            recyclerView.getContext(), 
            DividerItemDecoration.VERTICAL
        );
        // ใช้ Custom Drawable (res/drawable/divider.xml)
        dividerItemDecoration.setDrawable(ContextCompat.getDrawable(this, R.drawable.divider));
        recyclerView.addItemDecoration(dividerItemDecoration);

        // ข้อมูลทดสอบ
        for (int i = 0; i < 5; i++) {
            list.add("sairamm");
            list.add("Krishna");
            list.add("prasad");
        }
    }
}

ขั้นตอนที่ 4: สร้าง CustomAdapter.java

package com.example.myapplication;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.ArrayList;

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.MyViewHolder> {
    Context context;
    ArrayList<String> list;
    OnClickInterface onClickInterface;

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView title;
        public MyViewHolder(View view) {
            super(view);
            title = view.findViewById(R.id.title);
        }
    }

    public CustomAdapter(Context context, ArrayList<String> list, OnClickInterface onClickInterface) {
        this.context = context;
        this.list = list;
        this.onClickInterface = onClickInterface;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View itemView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.list_row, viewGroup, false);
        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder myViewHolder, final int i) {
        myViewHolder.title.setText(list.get(i));
        myViewHolder.title.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onClickInterface.setClick(i);
            }
        });
    }

    @Override
    public int getItemCount() {
        return list.size();
    }
}

ขั้นตอนที่ 5: เพิ่มโค้ดใน res/layout/list_row.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:app="https://schemas.android.com/apk/res-auto"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:cardElevation="10dp"
    app:cardCornerRadius="20dp"
    tools:context=".MainActivity">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="vertical">
        <ImageView
            android:id="@+id/imageView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/logo" />
        <TextView
            android:id="@+id/title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:textSize="30sp" />
        <TextView
            android:id="@+id/textview2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="Sairamkrishan"
            android:textSize="30sp" />
    </LinearLayout>
</android.support.v7.widget.CardView>

ขั้นตอนที่ 6: สร้าง Interface OnClickInterface

package com.example.myapplication;

public interface OnClickInterface {
    void setClick(int abc);
}

ขั้นตอนที่ 7: สร้าง Divider Drawable (res/drawable/divider.xml)

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="https://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@color/colorPrimary"/>
    <size android:height="2dp"/>
</shape>

การทดสอบแอปพลิเคชัน

รันแอปพลิเคชันบนอุปกรณ์ Android จริง ใน Android Studio คลิกไอคอน Run เลือกอุปกรณ์ แล้วตรวจสอบหน้าจอเริ่มต้น

สรุปวิธีเพิ่ม Divider/Spacing

ItemDecoration แบบ Custom (สำหรับ Spacing ทุกด้าน)

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {
    private final int spanCount;
    private final int spacing;
    private final boolean includeEdge;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view);
        int column = position % spanCount;

        if (includeEdge) {
            outRect.left = spacing - column * spacing / spanCount;
            outRect.right = (column + 1) * spacing / spanCount;
            if (position < spanCount) outRect.top = spacing;
            outRect.bottom = spacing;
        } else {
            outRect.left = column * spacing / spanCount;
            outRect.right = spacing - (column + 1) * spacing / spanCount;
            if (position >= spanCount) outRect.top = spacing;
            outRect.bottom = 0;
        }
    }
}