public class MainActivity extends AppCompatActivity {

@Override
 protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setTitle("10-3");
final RadioGroup radioGroup = (RadioGroup) findViewById(R.id.radioGroup);
final EditText edtNum1 = (EditText) findViewById(R.id.edtNum1);
final EditText edtNum2 = (EditText) findViewById(R.id.edtNum2);
final RadioButton radioButton4 = (RadioButton) findViewById(R.id.radioButton4);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
 public void onClick(View v) {

Intent intent = new Intent(getApplicationContext(), SecondActivity.class);
switch (radioGroup.getCheckedRadioButtonId()){
case R.id.radioButton1:
intent.putExtra("Calc", "+");
break;
case R.id.radioButton2:
intent.putExtra("Calc", "-");
break;
case R.id.radioButton3:
intent.putExtra("Calc", "*");
break;
case R.id.radioButton4:
intent.putExtra("Calc", "/");
break;
default:
Toast.makeText(MainActivity.this, "사칙연산을 선택", Toast.LENGTH_SHORT).show();
break;
}
intent.putExtra("Num1", Integer.parseInt(edtNum1.getText().toString()));
intent.putExtra("Num2", Integer.parseInt(edtNum2.getText().toString()));
startActivityForResult(intent, 0);

}
});


}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == RESULT_OK) {
int hap = data.getIntExtra("result", 0);
Toast.makeText(getApplicationContext(), "계산결과 :" + hap, Toast.LENGTH_SHORT).show();
}
}
}



public class SecondActivity extends AppCompatActivity{
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.second);
setTitle("Second 액티비티");
Intent inIntent = getIntent();
String calc = inIntent.getStringExtra("Calc");
int Result = 0;
if(calc.equals("+")){
Result = inIntent.getIntExtra("Num1", 0) + inIntent.getIntExtra("Num2", 0);
}
else if(calc.equals("-")){
Result = inIntent.getIntExtra("Num1", 0) - inIntent.getIntExtra("Num2", 0);
}
else if(calc.equals("*")){
Result = inIntent.getIntExtra("Num1", 0) * inIntent.getIntExtra("Num2", 0);
}
else if(calc.equals("/")){
Result = inIntent.getIntExtra("Num1", 0) / inIntent.getIntExtra("Num2", 0);
}


final int result = Result;
Button btnReturn = (Button) findViewById(R.id.btnReturn);
btnReturn.setOnClickListener(new View.OnClickListener() {
@Override
 public void onClick(View v) {

Intent outIntent = new Intent(getApplicationContext(), MainActivity.class);
outIntent.putExtra("result", result);
setResult(RESULT_OK, outIntent);
finish();


}
});

}
}