Data request to the web server 웹서버에 데이터 요청하고 응답 받기

웹서버에 데이터를 요청하고 app에서 응답 받아 처리할 수 있다.

서버에서 전달 되는 데이터 형식(Json)

{
    "LastUpdate":"2019.10.12",
    "SalesRecord":
    [
        {"date":"2016.03.08","item":"apple","price":2400,"quantity":84,"total":201600},
        {"date":"2016.07.29","item":"grape","price":3100,"quantity":37,"total":114700},
        {"date":"2017.10.25","item":"peach","price":4600,"quantity":55,"total":253000},
        {"date":"2018.12.08","item":"banana","price":1500,"quantity":83,"total":124500},
        {"date":"2019.05.09","item":"melon","price":7200,"quantity":75,"total":540000},
        {"date":"2019.10.17","item":"coconut","price":6800,"quantity":59,"total":401200},
        {"date":"2019.11.07","item":"strawberry","price":4900,"quantity":30,"total":147000}
    ]
}

<AndroidManifest.xml>

    <uses-permission android:name="android.permission.INTERNET"/>
 
    <application
        android:usesCleartextTraffic="true">
        <!--
        android:usesCleartextTraffic
        Indicates whether the app intends to use cleartext network traffic, such as cleartext HTTP.
        The default value for apps that target API level 27 or lower is "true". Apps that target
        API level 28 or higher default to "false". When the attribute is set to "false", platform
        components (for example, HTTP and FTP stacks, DownloadManager, and MediaPlayer) will refuse
        the app's requests to use cleartext traffic. Third-party libraries are strongly encouraged
        to honor this setting as well. The key reason for avoiding cleartext traffic is the lack of
        confidentiality, authenticity, and protections against tampering; a network attacker can
        eavesdrop on transmitted data and also modify it without being detected.
        -->

<MainActivity.java>

public class MainActivity extends AppCompatActivity {
 
    EditText editText;
    TextView textView;
 
    static RequestQueue requestQueue;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        editText = findViewById(R.id.editText);
        textView = findViewById(R.id.textView);
 
        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                makeRequest();
            }
        });
 
        if (requestQueue == null) {
            requestQueue = Volley.newRequestQueue(getApplicationContext());
        }
    }
 
    public void makeRequest() {
        String url = editText.getText().toString();
        StringRequest request = new StringRequest(Request.Method.GET, url,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        try {
                            //Server(Ubuntu) data encoding
                            response = new String(response.getBytes("iso-8859-1"), "utf-8");
                            //textView.append("Raw data: " + response);
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
 
                        Gson gson = new Gson();
                        RequestResult requestResult = gson.fromJson(response, RequestResult.class);
                        textView.setText("Items count: " + requestResult.SalesRecord.size() + '\n');
                        textView.append("Last Update: " + requestResult.LastUpdate + '\n');
                        ArrayList<Data> items = requestResult.SalesRecord;
                        for (int i = 0; i < items.size(); i++) {
                            textView.append(String.format("■ Date: %s, Item: %s, Price: %s, Quantity: %s, Total: %s\n",
                                    items.get(i).date, items.get(i).item, items.get(i).price, items.get(i).quantity, items.get(i).total));
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        textView.append("Error: " + error.getMessage());
                    }
                }
        ) {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String, String> params = new HashMap<String, String>();
 
                return params;
            }
        };
 
        request.setShouldCache(false);
        requestQueue.add(request);
        textView.setText("Request sent.");
    }
}

<RequestResult.java>

public class RequestResult {
    String LastUpdate;
    ArrayList<Data> SalesRecord = new ArrayList<Data>();
}

서버 데이터의 key와 같은 이름의 변수를 만들어야 한다.

<Data.java>

public class Data {
    String date;
    String item;
    String price;
    String quantity;
    String total;
}

서버 데이터의 key와 같은 이름의 변수를 만들어야 한다

실행 화면. 서버 주소를 입력하고 DATA REQUEST 버튼을 클릭한다.

서버부터 전달된 데이터가 지정한 대로 표시된다.