HttpURLConnection 사용법

* MainActivity.java

public class MainActivity extends AppCompatActivity {

    EditText editText;
    TextView textView;

    Handler handler = new Handler();

    @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 v) {
                final String urlStr = editText.getText().toString();

                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        request(urlStr);
                    }
                }).start();
            }
        });
    }

    public void request(String urlStr) {
        try {
            StringBuilder builder = new StringBuilder();

            URL url = new URL(urlStr);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            if (conn != null) {
                conn.setConnectTimeout(10000);
                conn.setRequestMethod("GET");
                conn.setDoInput(true);

                int resCode = conn.getResponseCode();

                BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                String line = null;
                while (true) {
                    line = reader.readLine();
                    if (line == null) {
                        break;
                    }

                    builder.append(line + "\n");
                }

                reader.close();
                conn.disconnect();
            }

            println("응답 : " + builder.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void println(final String data) {
        handler.post(new Runnable() {
            @Override
            public void run() {
                textView.append(data + "\n");
            }
        });
    }

}

* activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="http://www.google.com" />

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="요청" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/textView"
                android:textSize="20dp"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />
        </LinearLayout>

    </ScrollView>

</LinearLayout>

* AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />
<application android:usesCleartextTraffic="true" />