Volley 사용하여 게시판 리스트 가져와서 출력하기 2/3

- 안드로이드에서 해당 페이지로부터 데이터를 가져오는 작업.

3-1. build.gradle에 Volley 추가

implementation 'com.android.volley:volley:1.1.1'

3-2. 게시판 리스트를 출력할 Layout 작성 - activity_board.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FAFAFA">

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:gravity="center"
        android:background="#FFF"
        android:textSize="20dp"
        android:textColor="#666"
        android:text="게시글 목록"/>

    <ImageView
        android:id="@+id/img_close"
        android:layout_width="28dp"
        android:layout_height="28dp"
        android:src="@drawable/btn_close"
        android:layout_marginTop="11dp"
        android:layout_marginEnd="18dp"
        android:layout_alignParentEnd="true"/>

    <View
        android:id="@+id/viewline_01"
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:layout_below="@id/title"
        android:background="#EEE" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_below="@id/viewline_01">

        <ListView
            android:id="@+id/listview"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:dividerHeight="1dp"
            android:divider="#EEE"
            android:background="@drawable/custom_bg_01"/>

    </LinearLayout>

    <ProgressBar
        android:id="@+id/progressBar"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:alpha="0.3"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:visibility="gone" />

</RelativeLayout>

※ 화면은 다음과 같다.

4. Volley 객체를 생성한다. (싱글톤 패턴 적용)

public class MyVolley {
  private static MyVolley instance;
  private RequestQueue requestQueue;

  public static MyVolley getInstance(Context context) {
    if(instance == null)
      instance = new MyVolley(context);
    return instance;
  }

  private MyVolley(Context context) {
    requestQueue = Volley.newRequestQueue(context);
  }

  public RequestQueue getRequestQueue() {
    return requestQueue;
  }
}

4.서버사이드 VO와 동일한 Board VO를 생성해준다. (동일하므로 생략)

5. Volley 객체를 이용하여 게시판 데이터를 가져온다.

public class BoardActivity extends Activity {
  private Context mContext
  private ListView mListView;
  private ProgressBar progressBar;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mContext = this;
    setContentView(R.layout.activity_board);    

    mListView = findViewById(R.id.listview);
    progressBar = findViewById(R.id.progressBar);
    ImageView btnClose = findViewById(R.id.img_close);
    btnClose.setOnClickListener(new View.OnClickListener() { // X 버튼
      @Override
      public void onClick(View view) {
        finish();
      }
    });

    getBoardData(); // 게시판 데이터 가져오기
  }
  
  private void setProgressBar(int visibility) {
    progressBar.setVisibility(visibility);
  }

  private void getBoardData() {
    setProgressBar(View.VISIBLE);
    final String url = getString(R.string.url_get_board); // 서버사이드 페이지 웹 주소 
    RequestQueue queue = MyVolley.getInstance(mContext).getRequestQueue();
    JsonObjectRequest jsonRequest = new JsonObjectRequest(Request.Method.GET, url, new JSONObject(),
                                                          successListener(), errorListener());
    queue.add(jsonRequest);
  }
 
  private void parsingJSONData(String data) {
    List<Board> mList = new ArrayList<>();
    try {
      JSONArray jArray = new JSONArray(data);
      for(int i = 0; i < jArray.length(); i++) {
        Board board = new Board();
        JSONObject jObject = jArray.getJSONObject(i);
        board.setNno(Integer.parseInt(jObject.getString("nno")));
        board.setTitle(jObject.getString("title"));
        board.setContent(jObject.getString("content"));
        board.setCreateDate(jObject.getString("createDatet"));
        mList.add(board );
      }
      mListView.setAdapter(new BoardAdapter(mList));

    } catch(JSONException e) {
      e.printStackTrace();
    }
  }

  private Response.Listener<JSONObject> successListener() {
    return new Response.Listener<JSONObject>() {
      @Override
      public void onResponse(JSONObject response) {
        setProgressBar(View.GONE);
        String result = null;
        try {
          result = response.getString("data");
        } catch(JSONException e) {
          e.printStackTrace();
        }
        parsingJSONData(result);
      }
    };
  }

  private Response.ErrorListener errorListener() {
    return new Response.ErrorListener() {
      @Override
      public void onErrorResponse(VolleyError error) {
        // Util.showToast(mContext, getString(R.string.msg_network_error_01));
        // 에러 메시지 작성
      }
    };
  }
}