기능

1. 숫자1, 숫자2 입력 받기 <EditText> 2개
2. 더하기, 빼기, 곱하기, 나누기 <Button> 4개
3. 결과 출력 <TextView> 1개

XML 코드 : 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/Edit1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:hint="숫자1" />

    <EditText
        android:id="@+id/Edit2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:hint="숫자2" />

    <Button
        android:id="@+id/BtnAdd"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="더하기" />

    <Button
        android:id="@+id/BtnSub"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="빼기" />

    <Button
        android:id="@+id/BtnMul"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="곱하기" />

    <Button
        android:id="@+id/BtnDiv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="나누기" />

    <TextView
        android:id="@+id/TextResult"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="계산 결과 : "
        android:textColor="#FF0000"
        android:textSize="30dp" />

</LinearLayout>

JAVA 코드 : MainActivity.java

package com.cookandroid.project4_1;

import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    EditText edit1, edit2;
    Button btnAdd, btnSub, btnMul, btnDiv;
    TextView textResult;
    String num1, num2;
    Integer result;

    @Override
    protected void onCreate(Bundle savedInstanceState) { //메인 메소드
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        setTitle("초간단 계산기");

        edit1 = (EditText) findViewById(R.id.Edit1);
        edit2 = (EditText) findViewById(R.id.Edit2);

        btnAdd = (Button) findViewById(R.id.BtnAdd);
        btnSub = (Button) findViewById(R.id.BtnSub);
        btnMul = (Button) findViewById(R.id.BtnMul);
        btnDiv = (Button) findViewById(R.id.BtnDiv);

        textResult = (TextView) findViewById(R.id.TextResult);

        btnAdd.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View arg0, MotionEvent arg1) {
                num1 = edit1.getText().toString();
                num2 = edit2.getText().toString();
                result = Integer.parseInt(num1) + Integer.parseInt(num2);
                textResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });

        btnSub.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View arg0, MotionEvent arg1) {
                num1 = edit1.getText().toString();
                num2 = edit2.getText().toString();
                result = Integer.parseInt(num1) - Integer.parseInt(num2);
                textResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });

        btnMul.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View arg0, MotionEvent arg1) {
                num1 = edit1.getText().toString();
                num2 = edit2.getText().toString();
                result = Integer.parseInt(num1) * Integer.parseInt(num2);
                textResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });

        btnDiv.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View arg0, MotionEvent arg1) {
                num1 = edit1.getText().toString();
                num2 = edit2.getText().toString();
                result = Integer.parseInt(num1) / Integer.parseInt(num2);
                textResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });

    }
}

---

결과물

초기 화면 :

더하기 :

빼기 :

곱하기 :

나누기 :