Cách parse JSON Object trong Android với RecyclerView

Giới thiệu

Ví dụ này minh họa cách đọc file JSON từ thư mục assets, parse JSONObject/JSONArray và hiển thị danh sách dữ liệu trong RecyclerView với CardView.

Các bước thực hiện

Bước 1: Tạo dự án mới

Mở Android Studio, chọn File → New Project và điền thông tin cần thiết.

Bước 2: Cấu hình Gradle (build.gradle)

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.android.support:recyclerview-v7:28.0.0'
    implementation 'com.android.support:cardview-v7:28.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

Bước 3: Layout chính (activity_main.xml)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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="match_parent"
    tools:context=".MainActivity">
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</RelativeLayout>

Bước 4: Layout item (rowlayout_main.xml)

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:card_view="https://schemas.android.com/apk/res-auto"
    android:id="@+id/cardView"
    android:layout_width="match_parent"
    android:layout_margin="5dp"
    android:layout_height="wrap_content">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="10dp">
        <TextView
            android:id="@+id/tvName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Name"
            android:textColor="#000"
            android:textSize="20sp" />
        <TextView
            android:id="@+id/tvEmail"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="email@email.com"
            android:textColor="#000"
            android:textSize="15sp" />
        <TextView
            android:id="@+id/tvMobile"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="0999999999"
            android:textColor="#000"
            android:textSize="15sp" />
    </LinearLayout>
</android.support.v7.widget.CardView>

Bước 5: File JSON (assets/users_list.json)

{
  "users": [
    {
      "name": "Nguyễn Văn A",
      "email": "nguyenvana@example.com",
      "contact": { "mobile": "0901234567" }
    },
    {
      "name": "Trần Thị B",
      "email": "tranthib@example.com",
      "contact": { "mobile": "0912345678" }
    }
  ]
}

Bước 6: MainActivity.java - Parse JSON

package com.example.sample;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    ArrayList<String> personNames = new ArrayList<>();
    ArrayList<String> emailIds = new ArrayList<>();
    ArrayList<String> mobileNumbers = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        RecyclerView recyclerView = findViewById(R.id.recyclerView);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(linearLayoutManager);
        
        try {
            JSONObject obj = new JSONObject(loadJSONFromAsset());
            JSONArray userArray = obj.getJSONArray("users");
            
            for (int i = 0; i < userArray.length(); i++) {
                JSONObject userDetail = userArray.getJSONObject(i);
                personNames.add(userDetail.getString("name"));
                emailIds.add(userDetail.getString("email"));
                
                JSONObject contact = userDetail.getJSONObject("contact");
                mobileNumbers.add(contact.getString("mobile"));
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
        
        CustomAdapter customAdapter = new CustomAdapter(MainActivity.this, personNames, emailIds, mobileNumbers);
        recyclerView.setAdapter(customAdapter);
    }

    public String loadJSONFromAsset() {
        String json = null;
        try {
            InputStream is = getAssets().open("users_list.json");
            int size = is.available();
            byte[] buffer = new byte[size];
            is.read(buffer);
            is.close();
            json = new String(buffer, "UTF-8");
        } catch (IOException ex) {
            ex.printStackTrace();
            return null;
        }
        return json;
    }
}

Bước 7: CustomAdapter.java

package com.example.sample;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.MyViewHolder> {
    ArrayList<String> personNames, emailIds, mobileNumbers;
    Context context;

    public CustomAdapter(Context context, ArrayList<String> personNames, ArrayList<String> emailIds, ArrayList<String> mobileNumbers) {
        this.context = context;
        this.personNames = personNames;
        this.emailIds = emailIds;
        this.mobileNumbers = mobileNumbers;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.rowlayout, parent, false);
        return new MyViewHolder(v);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, final int position) {
        holder.name.setText(personNames.get(position));
        holder.email.setText(emailIds.get(position));
        holder.mobileNo.setText(mobileNumbers.get(position));
        
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(context, personNames.get(position), Toast.LENGTH_SHORT).show();
            }
        });
    }

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

    public class MyViewHolder extends RecyclerView.ViewHolder {
        TextView name, email, mobileNo;
        public MyViewHolder(View itemView) {
            super(itemView);
            name = itemView.findViewById(R.id.tvName);
            email = itemView.findViewById(R.id.tvEmail);
            mobileNo = itemView.findViewById(R.id.tvMobile);
        }
    }
}

Bước 8: Manifest (AndroidManifest.xml)

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android" package="com.example.sample">
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

Chạy ứng dụng

Kết nối thiết bị, nhấn Run. Danh sách user từ JSON sẽ hiển thị trong RecyclerView.

Thực tế: Nên dùng thư viện Gson hoặc Moshi để parse JSON tự động thành object (POJO), giảm code boilerplate và ít lỗi hơn.