[Android Studio] A부터 B까지 합 C 구하기

MainActivity3.java

package kr.co.aiai.app;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity3 extends AppCompatActivity {
    EditText et1;
    EditText et2;
    EditText et3;
    Button btn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);

        et1 = findViewById(R.id.et1);
        et2 = findViewById(R.id.et2);
        et3 = findViewById(R.id.et3);
        btn = findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                sumNumber();
            }
        });

    }

    public void sumNumber(){
        int a = Integer.parseInt(et1.getText()+"");
        int b = Integer.parseInt(et2.getText()+"");
        int sum= 0;
        for(int i = a; i<=b; i++){
            sum += i;
        }
        et3.setText(sum+"");
    }

}

 

activity_main3.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">

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

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="horizontal">


            <EditText
                android:id="@+id/et1"
                android:layout_width="50dp"
                android:layout_height="wrap_content"
                android:text="1"
                android:inputType="number" />


            <TextView
                android:id="@+id/tv"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:text="에서" />

            <EditText
                android:id="@+id/et2"
                android:layout_width="50dp"
                android:layout_height="wrap_content"
                android:text="10"
                android:inputType="number" />


            <Button
                android:id="@+id/btn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:text="까지합은" />


            <EditText
                android:id="@+id/et3"
                android:layout_width="50dp"
                android:layout_height="wrap_content"

                android:inputType="number" />

        </LinearLayout>
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>