StartActivityForResult

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"
    tools:context=".MainActivity3">

    <TextView
        android:id="@+id/tv_comeback"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:hint="값을 가져와주세요"/>

    <Button
        android:id="@+id/btn_go"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="GO"/>

</LinearLayout>

 

sub.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"
    tools:context=".SubActivity">

    <EditText
        android:id="@+id/et_comeback"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="Main으로 보낼 값 입력해주세요"/>

    <Button
        android:id="@+id/btn_close"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="종료"/>

</LinearLayout>

 

 

---

main.java

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private TextView tv_comeback;
    private Button btn_go;

    private  static  final  int REQUEST_CODE = 777;     //  상수 값을 선언  *상수(항상 같은 수 + 변하지 않을 수)

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

        tv_comeback = findViewById(R.id.tv_comeback);
        btn_go = findViewById(R.id.btn_go);

        btn_go.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(getApplicationContext(), SubActivity.class);
                startActivityForResult(intent, REQUEST_CODE);
            }
        });

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode,  Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == REQUEST_CODE) {  // requestCode로 비교해야 함
            if (resultCode == RESULT_OK) {
                Toast.makeText(getApplicationContext(), "수신 성공", Toast.LENGTH_SHORT).show();

                String resultText = data.getStringExtra("value");
                tv_comeback.setText(resultText);
            } else {
                Toast.makeText(getApplicationContext(), "수신 실패", Toast.LENGTH_SHORT).show();
            }

            }
        }
}

 

sub.java

public class SubActivity extends AppCompatActivity {
    private EditText et_comeback;
    public Button btn_close;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sub);

        et_comeback = findViewById(R.id.et_comeback);
        btn_close = findViewById(R.id.btn_close);

        btn_close.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent();
                intent.putExtra("value",et_comeback.getText().toString());   //입력폼에 적은 값 담아주기
                setResult(RESULT_OK, intent);   // 결과 값 설정
                finish();   // 현재 액티비티 종료
            }
        });
    }
}

---

결과 값