How to detect calls in an android device?

This example demonstrates how do I detect phone calls 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"?>
<RelativeLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Hello World!"
      android:textStyle="bold"
      android:textColor="@color/colorPrimary"
      android:layout_centerInParent="true" />
</RelativeLayout>

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

import android.Manifest;
import android.content.pm.PackageManager;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_PHONE_STATE) != PackageManager.PERMISSION_GRANTED){
         if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, Manifest.permission.READ_PHONE_STATE)){
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.READ_PHONE_STATE}, 1);
         }else{
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.READ_PHONE_STATE}, 1);
         }
      }else{
         notify();
      }
   }
   @Override
   public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults){
      switch (requestCode){
         case 1: {
            if (grantResults.length>0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
               if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_PHONE_STATE)==PackageManager.PERMISSION_GRANTED){
                  Toast.makeText(this, "Permission Granted", Toast.LENGTH_SHORT).show();
               }
            }else{
               Toast.makeText(this, "Permission Denied",
              Toast.LENGTH_SHORT).show();
            }
            return;
         }
      }  
   }
}

Step 4 − Create a java class (DetectCalls) and add the following code in DetectCalls.java

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;
public class DetectCalls extends BroadcastReceiver {
   @Override
   public void onReceive(Context context, Intent intent) {
      try{
         Toast.makeText(context, "Ringing!",
         Toast.LENGTH_SHORT).show();
      }catch (Exception e){
         e.printStackTrace();
      }
   }
}

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">
   <uses-permission android:name="android.permission.READ_PHONE_STATE"/>
   <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=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
      <receiver android:name=".DetectCalls">
         <intent-filter>
            <action android:name="android.intent.action.PHONE_STATE"/>
         </intent-filter>
      </receiver>
   </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.