Volley 사용법

* 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 v) {
                String urlStr = editText.getText().toString();
                request(urlStr);
            }
        });

        requestQueue = Volley.newRequestQueue(getApplicationContext());
    }

    public void request(String urlStr) {
        StringRequest request = new StringRequest(
                Request.Method.GET,
                urlStr,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        println("응답 :" + response);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        println("에러 : " + error.toString());
                    }
                }
        ) {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String, String> params = new HashMap<String, String>();

                return params;
            }
        };

        request.setShouldCache(false);
        requestQueue.add(request);
        println("요청 보냄");
    }

    public void println(String data) {
        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>

* Gradle

dependencies {
    implementation 'com.android.volley:volley:1.1.0'
}

* AndroidManifest.xml

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