Detecting incoming and outgoing phone calls on Android.

In this article i'll show you how to detect incoming and outgoing phone calls on Android platform.
It can be useful, if you need to perform some action when call is made. For example, to block it, to log it, or send call info to a server.

Article gives the step-by-step instructions, how to create the simple demo app, that will detect incoming and outgoing phone calls, show "toast" message with phone number. You can extends and use this code for your own needs.

Incoming calls.

For incoming calls we need to use TelephonyManager class, and it's method listen, to register a listener, that will receive call state, data connection, network, sim and other events, related to telephony. We are interested only in the call state notifications.

This requires android.permission.READ_PHONE_STATE permission.

So, create our listener class, derived from PhoneStateListener, and override onCallStateChanged method, as follows:

 
 /**
  * Listener to detect incoming calls. 
  */
 private class CallStateListener extends PhoneStateListener {
  @Override
  public void onCallStateChanged(int state, String incomingNumber) {
      switch (state) {
          case TelephonyManager.CALL_STATE_RINGING:
          // called when someone is ringing to this phone
    
          Toast.makeText(ctx, 
                  "Incoming: "+incomingNumber, 
                  Toast.LENGTH_LONG).show();
          break;
      }
  }
 }

Now i'll explain onCallStateChanged method.

First argument - state is call state, it can be CALL_STATE_RINGING, CALL_STATE_OFFHOOK or CALL_STATE_IDLE. Ringing is state when someone is calling us, offhook is when there is active or on hold call,  and idle - is when nobody is calling us and there is no active call. We are interested in ringing state.

Second argument - incomingNumber, it's number who is calling us.

As shown in code above, listener show the "toast" message with phone number, when incoming call is ringing.

Next, get instance of TelephonyManager and register listener:

  tm = (TelephonyManager) ctx.getSystemService(Context.TELEPHONY_SERVICE);
  tm.listen(callStateListener, PhoneStateListener.LISTEN_CALL_STATE);

When app is no longer need to receive notifications, it must unregister a listener by call:

  tm.listen(callStateListener, PhoneStateListener.LISTEN_NONE);

Outgoing calls.

For outgoing calls, system sends broadcast action android.intent.action.NEW_OUTGOING_CALL. We need to make broadcast receiver, that will receive intent with this action.

To receive this broadcast the android.permission.PROCESS_OUTGOING_CALLS permission is required.

Create broadcast receiver class:

 /**
  * Broadcast receiver to detect the outgoing calls.
  */
 public class OutgoingReceiver extends BroadcastReceiver {
     public OutgoingReceiver() {
     }

     @Override
     public void onReceive(Context context, Intent intent) {
         String number = intent.getStringExtra(Intent.EXTRA_PHONE_NUMBER);
         
         Toast.makeText(ctx, 
           "Outgoing: "+number, 
           Toast.LENGTH_LONG).show();
     }
  
 }

As with incoming calls, this code will show "toast" message, with phone number, when there is outgoing call.

Register the broadcast receiver:

  IntentFilter intentFilter = new IntentFilter(Intent.ACTION_NEW_OUTGOING_CALL);
  ctx.registerReceiver(outgoingReceiver, intentFilter);

We finished with the calls detection code. And how need to create an activity, that will enable/disable calls detection. It will be activity with simple UI, with textview showing detection status, button to enable/disable detection, and exit button.

But, here is the another issue - when our activity losses focus, calls detection is disabled. To prevent this, we have to make service, that will run  that will enable detection on start, and disable on stop.

Create the service:

/**
 * Call detect service. 
 * This service is needed, because MainActivity can lost it's focus,
 * and calls will not be detected.
 * 
 * @author Moskvichev Andrey V.
 *
 */
public class CallDetectService extends Service {
    private CallHelper callHelper;
 
    public CallDetectService() {
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        callHelper = new CallHelper(this);
  
        int res = super.onStartCommand(intent, flags, startId);
        callHelper.start();
        return res;
    }
 
    @Override
    public void onDestroy() {
        super.onDestroy();
  
        callHelper.stop();
    }

    @Override
    public IBinder onBind(Intent intent) {
        // not supporting binding
        return null;
   }
}

Create the activity.

Get UI elements and set onclick button handlers:

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        textViewDetectState = (TextView) findViewById(R.id.textViewDetectState);
        
        buttonToggleDetect = (Button) findViewById(R.id.buttonDetectToggle);
        buttonToggleDetect.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
                 setDetectEnabled(!detectEnabled);
             }
        });
        
        buttonExit = (Button) findViewById(R.id.buttonExit);
        buttonExit.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
                 setDetectEnabled(false);
                 MainActivity.this.finish();
             }
        });
    }

Create setDetectEnabled method, that will toggle calls detection:

    private void setDetectEnabled(boolean enable) {
        detectEnabled = enable;
     
        Intent intent = new Intent(this, CallDetectService.class);
        if (enable) {
              // start detect service 
              startService(intent);
            
              buttonToggleDetect.setText("Turn off");
              textViewDetectState.setText("Detecting");
        }
        else {
              // stop detect service
              stopService(intent);
      
              buttonToggleDetect.setText("Turn on");
              textViewDetectState.setText("Not detecting");
        }
    }

AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.bitgriff.androidcalls"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />
    
   <!--
         Permissions required for calls detection.
        -->
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
 <uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS" />
    
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service
            android:name=".CallDetectService"
            android:enabled="true"
            android:exported="false" >
        </service>
    </application>

</manifest>

Summary.
I shown you how to detect incoming and outgoing phone calls on Android. It a quite simple. Please, send me your comments and suggestions.

In the next articles, i'll show you other aspects of Android platform programming (networking, threads, multimedia processing, integration with websites and webservices, etc).

You can download source code for this article at: AndroidCalls.zip