Android studio 간단한 계산기 만들기

 

 

 

 

작동 영상

 

 

< MainActivity.java >

 

public class MainActivity extends AppCompatActivity {
    EditText editText;
    Button button;
    Button button2;
    Button button3;
    Button button4;
    Button button5;
    Button button6;
    Button button7;
    Button button8;
    Button button9;
    Button button10;
    Button button11;
    Button button0;
    Button button13;

    int x1, x2;
    char op;
    int result;

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

        findViewById(); //동기화
        click();            //클릭
    }

    private void findViewById(){
        button=findViewById(R.id.button);
        button2=findViewById(R.id.button2);
        button3=findViewById(R.id.button3);
        button4=findViewById(R.id.button4);
        button5=findViewById(R.id.button5);
        button6=findViewById(R.id.button6);
        button7=findViewById(R.id.button7);
        button8=findViewById(R.id.button8);
        button9=findViewById(R.id.button9);
        button10=findViewById(R.id.button10);
        button11=findViewById(R.id.button11);
        button0=findViewById(R.id.button0);
        button13=findViewById(R.id.button13);
    }

    private void click()
    {
        editText = findViewById(R.id.editText);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button.getText().toString();                     //버튼에서 얻어온 텍스트를 스트링으로
                editText.setText(s);                                       //editText에 셋(매개변수 : 스트링)
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button2.getText().toString();
                editText.setText(s);
            }
        });

        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button3.getText().toString();
                editText.setText(s);
            }
        });
        button4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button4.getText().toString();
                editText.setText(s);
            }
        });
        button5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button5.getText().toString();
                editText.setText(s);
            }
        });
        button6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button6.getText().toString();
                editText.setText(s);
            }
        });
        button7.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button7.getText().toString();
                editText.setText(s);
            }
        });
        button8.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button8.getText().toString();
                editText.setText(s);
            }
        });
        button9.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button9.getText().toString();
                editText.setText(s);
            }
        });

        button0.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString();            //기존 문자열 알기
                s += button0.getText().toString();
                editText.setText(s);
            }
        });

        //연산자
        button10.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                x1 = Integer.parseInt(editText.getText().toString());   
                op = '+';
                editText.setText("");
            }
        });
        button11.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                x1 = Integer.parseInt(editText.getText().toString());
                op = '-';
                editText.setText("");
            }
        });
        button13.setOnClickListener(new View.OnClickListener() { // = 연산자 계산
            @Override
            public void onClick(View v) {
                x2 = Integer.parseInt(editText.getText().toString());

                switch(op)
                {
                    case '+':
                        result = x1 + x2;
                        editText.setText(Integer.toString(result));
                        break;

                    case '-':
                        result = x1 - x2;
                        editText.setText(Integer.toString(result));
                        break;
                }
            }
        });
    }
}

 

 

< activity_main.xml >

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity"
    >

    <Button
        android:id="@+id/button5"                                    //아이디 생성
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="12dp"
        android:layout_marginTop="12dp"
        android:text="5"
        app:layout_constraintStart_toEndOf="@+id/button4"
        app:layout_constraintTop_toBottomOf="@+id/button2" />

    <Button
        android:id="@+id/button4"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="12dp"
        android:text="4"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

    <Button
        android:id="@+id/button6"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="20dp"
        android:layout_marginTop="12dp"
        android:text="6"
        app:layout_constraintStart_toEndOf="@+id/button5"
        app:layout_constraintTop_toBottomOf="@+id/button3" />

    <Button
        android:id="@+id/button2"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="12dp"
        android:layout_marginTop="20dp"
        android:text="2"
        app:layout_constraintStart_toEndOf="@+id/button"
        app:layout_constraintTop_toBottomOf="@+id/editText" />

    <Button
        android:id="@+id/button8"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="12dp"
        android:layout_marginTop="20dp"
        android:text="8"
        app:layout_constraintStart_toEndOf="@+id/button7"
        app:layout_constraintTop_toBottomOf="@+id/button5" />

    <Button
        android:id="@+id/button7"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="20dp"
        android:text="7"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button4" />

    <Button
        android:id="@+id/button9"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="24dp"
        android:layout_marginTop="20dp"
        android:text="9"
        app:layout_constraintStart_toEndOf="@+id/button8"
        app:layout_constraintTop_toBottomOf="@+id/button6" />

    <Button
        android:id="@+id/button11"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="12dp"
        android:layout_marginTop="16dp"
        android:text="-"
        app:layout_constraintStart_toEndOf="@+id/button10"
        app:layout_constraintTop_toBottomOf="@+id/button8" />

    <Button
        android:id="@+id/button0"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="24dp"
        android:layout_marginTop="16dp"
        android:text="0"
        app:layout_constraintStart_toEndOf="@+id/button11"
        app:layout_constraintTop_toBottomOf="@+id/button9" />

    <Button
        android:id="@+id/button10"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="16dp"
        android:text="+"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button7" />

    <Button
        android:id="@+id/button3"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="24dp"
        android:layout_marginTop="20dp"
        android:text="3"
        app:layout_constraintStart_toEndOf="@+id/button2"
        app:layout_constraintTop_toBottomOf="@+id/editText" />

    <Button
        android:id="@+id/button"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="20dp"
        android:text="1"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText" />

    <Button
        android:id="@+id/button13"
        android:layout_width="338dp"
        android:layout_height="68dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="12dp"
        android:text="="
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button11" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="343dp"
        android:layout_height="73dp"
        android:layout_marginStart="28dp"
        android:layout_marginTop="20dp"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:textStyle="bold"
        android:gravity="right"
        />

</androidx.constraintlayout.widget.ConstraintLayout>