How to send data back to the main Activity in android?

This example demonstrates how do I send data back to the main activity in android.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:orientation="vertical"
   android:gravity="center"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <EditText
      android:id="@+id/editTextNumber1"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:hint="Number 1"
      android:inputType="number" />
   <EditText
      android:id="@+id/editTextNumber2"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:hint="Number 2"
      android:inputType="number" />
   <TextView
      android:id="@+id/textViewResult"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="Result"
      android:textSize="30sp" />
   <Button
      android:id="@+id/btnOpenActivity2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="open activity 2" />
</LinearLayout>

Step 3 − Add the following code to src/MainActivity.java

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
   private TextView textViewResult;
   private EditText editTextNumber1;
   private EditText editTextNumber2;
   Button btnOpen;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      textViewResult = findViewById(R.id.textViewResult);
      editTextNumber1 = findViewById(R.id.editTextNumber1);
      editTextNumber2 = findViewById(R.id.editTextNumber2);
      btnOpen = findViewById(R.id.btnOpenActivity2);
      btnOpen.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            if (editTextNumber1.getText().toString().equals("")
               || editTextNumber2.getText().toString().equals("")) {
               Toast.makeText(MainActivity.this, "Please insert numbers", Toast.LENGTH_SHORT).show();
            } else {
               int number1 = Integer.parseInt(editTextNumber1.getText().toString());
               int number2 = Integer.parseInt(editTextNumber2.getText().toString());
               Intent intent = new Intent(MainActivity.this, SecondActivity.class);
               intent.putExtra("number1", number1);
               intent.putExtra("number2", number2);
               startActivityForResult(intent, 1);
            }
         }
      });
   }
   @Override
   protected void onActivityResult(int requestCode, int resultCode, Intent data) {
      super.onActivityResult(requestCode, resultCode, data);
      if (requestCode == 1) {
         if (resultCode == RESULT_OK) {
               nt result = data.getIntExtra("result", 0);
            textViewResult.setText("" + result);
         }
         if (resultCode == RESULT_CANCELED) {
            textViewResult.setText("Nothing selected");
         }
      }
   }
}

Step 4 – Create a new activity and add the following code −

Activity_second.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools"
   android:orientation="vertical"
   android:gravity="center"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <TextView
      android:id="@+id/textViewNumbers"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:text="Numbers: "
      android:textSize="30sp" />
   <Button
      android:id="@+id/buttonAdd"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="add" />
   <Button
      android:id="@+id/buttonSubtract"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="subtract" />
</LinearLayout>

SecondActivity.java

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class SecondActivity extends AppCompatActivity {
   TextView textViewNumber;
   Button buttonAdd, buttonSubtract;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_second);
      Intent intent = getIntent();
      final int number1 = intent.getIntExtra("number1", 0);
      final int number2 = intent.getIntExtra("number2", 0);
      textViewNumber = findViewById(R.id.textViewNumbers);
      textViewNumber.setText("Numbers: " + number1 + ", " + number2);
      buttonAdd = findViewById(R.id.buttonAdd);
      buttonSubtract = findViewById(R.id.buttonSubtract);
      buttonAdd.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            int result = number1 + number2;
            Intent resultIntent = new Intent();
            resultIntent.putExtra("result", result);
            setResult(RESULT_OK, resultIntent);
            finish();
         }
      });
      buttonSubtract.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            int result = number1 - number2;
            Intent resultIntent = new Intent();
            resultIntent.putExtra("result", result);
            setResult(RESULT_OK, resultIntent);
            finish();
         }
      });
   }
}

Step 5 – Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".SecondActivity"></activity>
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
   </activity>
</application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen –

Click here to download the project code.