1. activity_main.xml 코드

<?xml version="1.0" encoding="utf-8"?>
<TableLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:layout_margin="5dp">

    <TableRow
        android:layout_width="match_parent">
        <EditText
            android:id="@+id/etNum1"
            android:layout_span="4"
            android:hint="숫자 입력" />
    </TableRow>
    <TableRow>
        <EditText
            android:id="@+id/etNum2"
            android:layout_span="4"
            android:hint="숫자 입력" />
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/btnNum0"
            android:text="0"
            android:layout_weight="1"
            android:layout_margin="5dp"/>
        <Button
            android:id="@+id/btnNum1"
            android:text="1"
            android:layout_weight="1"
            android:layout_margin="5dp" />
        <Button
            android:id="@+id/btnNum2"
            android:text="2"
            android:layout_weight="1"
            android:layout_margin="5dp" />
        <Button
            android:id="@+id/btnNum3"
            android:text="3"
            android:layout_weight="1"
            android:layout_margin="5dp" />
        <Button
            android:id="@+id/btnNum4"
            android:text="4"
            android:layout_weight="1"
            android:layout_margin="5dp" />
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/btnNum5"
            android:text="5"
            android:layout_weight="1"
            android:layout_margin="5dp"/>
        <Button
            android:id="@+id/btnNum6"
            android:text="6"
            android:layout_weight="1"
            android:layout_margin="5dp" />
        <Button
            android:id="@+id/btnNum7"
            android:text="7"
            android:layout_weight="1"
            android:layout_margin="5dp" />
        <Button
            android:id="@+id/btnNum8"
            android:text="8"
            android:layout_weight="1"
            android:layout_margin="5dp" />
        <Button
            android:id="@+id/btnNum9"
            android:text="9"
            android:layout_weight="1"
            android:layout_margin="5dp" />
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/btnAdd"
            android:layout_span="4"
            android:layout_margin="5dp"
            android:text="더하기" />
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/btnMinus"
            android:layout_span="4"
            android:layout_margin="5dp"
            android:text="빼기" />
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/btnMul"
            android:layout_span="4"
            android:layout_margin="5dp"
            android:text="곱하기" />
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/btnDiv"
            android:layout_span="4"
            android:layout_margin="5dp"
            android:text="나누기" />
    </TableRow>
    <TableRow>
        <TextView
            android:id="@+id/tvResult"
            android:layout_span="4"
            android:text="계산 결과 : "
            android:textColor="@android:color/holo_red_light"
            android:textSize="20dp"
            android:layout_margin="5dp"/>
    </TableRow>

</TableLayout>

2. MainActivity.java 코드

public class MainActivity extends AppCompatActivity {

    private EditText etNum1, etNum2;
    private Button[] btn = new Button[14];
    private TextView tvResult;

    private String num1, num2;
    private Integer result;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setTitle("테이블레이아웃 계산기");

        init();
        initLr();
    }
    public void init(){
        etNum1 = findViewById(R.id.etNum1);
        etNum2 = findViewById(R.id.etNum2);
        tvResult = findViewById(R.id.tvResult);
        btn[0] = findViewById(R.id.btnNum0);
        btn[1] = findViewById(R.id.btnNum1);
        btn[2] = findViewById(R.id.btnNum2);
        btn[3] = findViewById(R.id.btnNum3);
        btn[4] = findViewById(R.id.btnNum4);
        btn[5] = findViewById(R.id.btnNum5);
        btn[6] = findViewById(R.id.btnNum6);
        btn[7] = findViewById(R.id.btnNum7);
        btn[8] = findViewById(R.id.btnNum8);
        btn[9] = findViewById(R.id.btnNum9);
        btn[10] = findViewById(R.id.btnAdd);
        btn[11] = findViewById(R.id.btnMinus);
        btn[12] = findViewById(R.id.btnMul);
        btn[13] = findViewById(R.id.btnDiv);
    }


    public void initLr(){
        btn[10].setOnTouchListener(new View.OnTouchListener(){
            public boolean onTouch(View arg0, MotionEvent arg1){
                num1 = etNum1.getText().toString();
                num2 = etNum2.getText().toString();
                result = Integer.parseInt(num1) + Integer.parseInt(num2);
                tvResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });
        btn[11].setOnTouchListener(new View.OnTouchListener(){
            public boolean onTouch(View arg0, MotionEvent arg1){
                num1 = etNum1.getText().toString();
                num2 = etNum2.getText().toString();
                result = Integer.parseInt(num1) - Integer.parseInt(num2);
                tvResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });
        btn[12].setOnTouchListener(new View.OnTouchListener(){
            public boolean onTouch(View arg0, MotionEvent arg1){
                num1 = etNum1.getText().toString();
                num2 = etNum2.getText().toString();
                result = Integer.parseInt(num1) * Integer.parseInt(num2);
                tvResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });
        btn[13].setOnTouchListener(new View.OnTouchListener(){
            public boolean onTouch(View arg0, MotionEvent arg1){
                num1 = etNum1.getText().toString();
                num2 = etNum2.getText().toString();
                result = Integer.parseInt(num1) / Integer.parseInt(num2);
                tvResult.setText("계산 결과 : " + result.toString());
                return false;
            }
        });

        for(int i = 0; i < 10; i++){
            final int index;
            index = i;

            btn[index].setOnClickListener(v -> {
                if(etNum1.isFocused() == true){
                    num1 = etNum1.getText().toString() + btn[index].getText().toString();
                    etNum1.setText(num1);
                } else if(etNum2.isFocused() == true) {
                    num2 = etNum2.getText().toString() + btn[index].getText().toString();
                    etNum2.setText(num2);
                } else {
                    Toast.makeText(getApplicationContext(), "먼저 에디트텍스트를 선택하세요",
                    			Toast.LENGTH_SHORT).show();
                }
            });
        }
    }
}