<receiver android:name=".receiver.CallReceiver">
            <intent-filter>
                <action android:name="android.intent.action.PHONE_STATE"/>
            </intent-filter>
        </receiver>

public class CallReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (TelephonyManager.ACTION_PHONE_STATE_CHANGED.equals(intent.getAction()) && "RINGING".equals(intent.getStringExtra(TelephonyManager.EXTRA_STATE))) {
            String number = intent.getStringExtra(TelephonyManager.EXTRA_INCOMING_NUMBER);
         
        }
    }
}