How to record phone calls in android?

Ok, for this first of all you need to use Device Policy Manager, and need to make your device Admin device. After that you have to create one BroadCast receiver and one service. I am posting code here and its working fine.

MainActivity:

public class MainActivity extends Activity {
    private static final int REQUEST_CODE = 0;
    private DevicePolicyManager mDPM;
    private ComponentName mAdminName;

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

        try {
            // Initiate DevicePolicyManager.
            mDPM = (DevicePolicyManager) getSystemService(Context.DEVICE_POLICY_SERVICE);
            mAdminName = new ComponentName(this, DeviceAdminDemo.class);

            if (!mDPM.isAdminActive(mAdminName)) {
                Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
                intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, mAdminName);
                intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION, "Click on Activate button to secure your application.");
                startActivityForResult(intent, REQUEST_CODE);
            } else {
                // mDPM.lockNow();
                // Intent intent = new Intent(MainActivity.this,
                // TrackDeviceService.class);
                // startService(intent);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } 
    }

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

        if (REQUEST_CODE == requestCode) {
                Intent intent = new Intent(MainActivity.this, TService.class);
                startService(intent);
        }
    }

}

//DeviceAdminDemo class

public class DeviceAdminDemo extends DeviceAdminReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        super.onReceive(context, intent);
    }

    public void onEnabled(Context context, Intent intent) {
    };

    public void onDisabled(Context context, Intent intent) {
    };
}

//TService Class

public class TService extends Service {
    MediaRecorder recorder;
    File audiofile;
    String name, phonenumber;
    String audio_format;
    public String Audio_Type;
    int audioSource;
    Context context;
    private Handler handler;
    Timer timer;
    Boolean offHook = false, ringing = false;
    Toast toast;
    Boolean isOffHook = false;
    private boolean recordstarted = false;

    private static final String ACTION_IN = "android.intent.action.PHONE_STATE";
    private static final String ACTION_OUT = "android.intent.action.NEW_OUTGOING_CALL";
    private CallBr br_call;




    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void onDestroy() {
        Log.d("service", "destroy");

        super.onDestroy();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // final String terminate =(String)
        // intent.getExtras().get("terminate");//
        // intent.getStringExtra("terminate");
        // Log.d("TAG", "service started");
        //
        // TelephonyManager telephony = (TelephonyManager)
        // getSystemService(Context.TELEPHONY_SERVICE); // TelephonyManager
        // // object
        // CustomPhoneStateListener customPhoneListener = new
        // CustomPhoneStateListener();
        // telephony.listen(customPhoneListener,
        // PhoneStateListener.LISTEN_CALL_STATE);
        // context = getApplicationContext();

        final IntentFilter filter = new IntentFilter();
        filter.addAction(ACTION_OUT);
        filter.addAction(ACTION_IN);
        this.br_call = new CallBr();
        this.registerReceiver(this.br_call, filter);

        // if(terminate != null) {
        // stopSelf();
        // }
        return START_NOT_STICKY;
    }

    public class CallBr extends BroadcastReceiver {
        Bundle bundle;
        String state;
        String inCall, outCall;
        public boolean wasRinging = false;

        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equals(ACTION_IN)) {
                if ((bundle = intent.getExtras()) != null) {
                    state = bundle.getString(TelephonyManager.EXTRA_STATE);
                    if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
                        inCall = bundle.getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
                        wasRinging = true;
                        Toast.makeText(context, "IN : " + inCall, Toast.LENGTH_LONG).show();
                    } else if (state.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)) {
                        if (wasRinging == true) {

                            Toast.makeText(context, "ANSWERED", Toast.LENGTH_LONG).show();

                            String out = new SimpleDateFormat("dd-MM-yyyy hh-mm-ss").format(new Date());
                            File sampleDir = new File(Environment.getExternalStorageDirectory(), "/TestRecordingDasa1");
                            if (!sampleDir.exists()) {
                                sampleDir.mkdirs();
                            }
                            String file_name = "Record";
                            try {
                                audiofile = File.createTempFile(file_name, ".amr", sampleDir);
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                            String path = Environment.getExternalStorageDirectory().getAbsolutePath();

                            recorder = new MediaRecorder();
//                          recorder.setAudioSource(MediaRecorder.AudioSource.VOICE_CALL);

                            recorder.setAudioSource(MediaRecorder.AudioSource.VOICE_COMMUNICATION);
                            recorder.setOutputFormat(MediaRecorder.OutputFormat.AMR_NB);
                            recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
                            recorder.setOutputFile(audiofile.getAbsolutePath());
                            try {
                                recorder.prepare();
                            } catch (IllegalStateException e) {
                                e.printStackTrace();
                            } catch (IOException e) { 
                                e.printStackTrace();
                            }
                            recorder.start();
                            recordstarted = true;
                        }
                    } else if (state.equals(TelephonyManager.EXTRA_STATE_IDLE)) {
                        wasRinging = false;
                        Toast.makeText(context, "REJECT || DISCO", Toast.LENGTH_LONG).show();
                        if (recordstarted) {
                            recorder.stop();
                            recordstarted = false;
                        }
                    }
                }
            } else if (intent.getAction().equals(ACTION_OUT)) {
                if ((bundle = intent.getExtras()) != null) {
                    outCall = intent.getStringExtra(Intent.EXTRA_PHONE_NUMBER);
                    Toast.makeText(context, "OUT : " + outCall, Toast.LENGTH_LONG).show();
                }
            }
        }
    }

}

//Permission in manifest file

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.STORAGE" />

//my_admin.xml

<device-admin xmlns:android="http://schemas.android.com/apk/res/android" >
    <uses-policies>
        <force-lock />
    </uses-policies>
</device-admin>

//Declare following thing in manifest:

Declare DeviceAdminDemo class to manifest:

 <receiver
            android:name="com.example.voicerecorder1.DeviceAdminDemo"
            android:description="@string/device_description"
            android:label="@string/device_admin_label"
            android:permission="android.permission.BIND_DEVICE_ADMIN" >
            <meta-data
                android:name="android.app.device_admin"
                android:resource="@xml/my_admin" />


            <intent-filter>
                <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
                <action android:name="android.app.action.DEVICE_ADMIN_DISABLED" />
                <action android:name="android.app.action.DEVICE_ADMIN_DISABLE_REQUESTED" />
            </intent-filter>
        </receiver>

<service android:name=".TService" >
        </service>

Below code is working for me to record a outgoing phone call

//Call Recording varibales
private static final String AUDIO_RECORDER_FILE_EXT_3GP = ".3gp";
private static final String AUDIO_RECORDER_FILE_EXT_MP4 = ".mp4";
private static final String AUDIO_RECORDER_FOLDER = "AudioRecorder";

private MediaRecorder recorder = null;
private int currentFormat = 0;
private int output_formats[] = { MediaRecorder.OutputFormat.MPEG_4,
        MediaRecorder.OutputFormat.THREE_GPP };
private String file_exts[] = { AUDIO_RECORDER_FILE_EXT_MP4,
        AUDIO_RECORDER_FILE_EXT_3GP };

AudioManager audioManager;

//put this methods to outside of oncreate() method

private String getFilename() {
    String filepath = Environment.getExternalStorageDirectory().getPath();
    File file = new File(filepath, AUDIO_RECORDER_FOLDER);

    if (!file.exists()) {
        file.mkdirs();
    }

    return (file.getAbsolutePath() + "/" + System.currentTimeMillis() + file_exts[currentFormat]);
}

private MediaRecorder.OnErrorListener errorListener = new MediaRecorder.OnErrorListener() {
    @Override
    public void onError(MediaRecorder mr, int what, int extra) {
        Toast.makeText(CallActivity.this,
                "Error: " + what + ", " + extra, Toast.LENGTH_SHORT).show();
    }
};

private MediaRecorder.OnInfoListener infoListener = new MediaRecorder.OnInfoListener() {
    @Override
    public void onInfo(MediaRecorder mr, int what, int extra) {
        Toast.makeText(CallActivity.this,
                "Warning: " + what + ", " + extra, Toast.LENGTH_SHORT)
                .show();
    }
};

//below part of code to make your device on speaker

    audioManager = (AudioManager)getApplicationContext().getSystemService(Context.AUDIO_SERVICE); 
    audioManager.setMode(AudioManager.MODE_IN_CALL);
    audioManager.setSpeakerphoneOn(true);

//below part of code to start recording

recorder = new MediaRecorder();
    recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    recorder.setOutputFormat(output_formats[currentFormat]);
    //recorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    recorder.setOutputFile(getFilename());
    recorder.setOnErrorListener(errorListener);
    recorder.setOnInfoListener(infoListener);

    try {
        recorder.prepare();
        recorder.start();
    } catch (IllegalStateException e) {
         Log.e("REDORDING :: ",e.getMessage());
            e.printStackTrace();
    } catch (IOException e) {
        Log.e("REDORDING :: ",e.getMessage());
        e.printStackTrace();
    }

//For stop recording and keep in mind to set speaker off while call end or stop

audioManager.setSpeakerphoneOn(false);

    try{
        if (null != recorder) {
            recorder.stop();
            recorder.reset();
            recorder.release();

            recorder = null;
        }
    }catch(RuntimeException stopException){

    }

And give permission to manifest file,

<uses-permission android:name="android.permission.CALL_PHONE" />
<uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

So, basically, I want to combine 2 answers, one from this post and one from another post that I read, don't know the author of it so please sorry for using your methods.

So, here are my classes for achieving desired result:

    public class StartActivity extends Activity {
    public static final int REQUEST_CODE = 5912;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        PackageManager p = getPackageManager();
        ComponentName componentName = new ComponentName(this, StartActivity.class); // activity which is first time open in manifiest file which is declare as <category android:name="android.intent.category.LAUNCHER" />
        p.setComponentEnabledSetting(componentName, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP);
        startService(new Intent(this, StartService.class));
        startService(new Intent(this, SmsOutgoingService.class));
        try {
            // Initiate DevicePolicyManager.
            DevicePolicyManager mDPM = (DevicePolicyManager) getSystemService(Context.DEVICE_POLICY_SERVICE);
            ComponentName mAdminName = new ComponentName(this, DeviceAdminReciever.class);

            if (!mDPM.isAdminActive(mAdminName)) {
                Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
                intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, mAdminName);
                intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION, "Click on Activate button to secure your application.");
                startActivityForResult(intent, REQUEST_CODE);
            } else {
                mDPM.lockNow();
                finish();
//                 Intent intent = new Intent(MainActivity.this,
//                 TrackDeviceService.class);
//                 startService(intent);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (REQUEST_CODE == requestCode) {
            startService(new Intent(StartActivity.this, TService.class));
            finish();
        }
        super.onActivityResult(requestCode, resultCode, data);
    }
}

And my TService class:

  public class TService extends Service {

    private MediaRecorder recorder;
    private File audiofile;
    private boolean recordstarted = false;

    private static final String ACTION_IN = "android.intent.action.PHONE_STATE";
    private static final String ACTION_OUT = "android.intent.action.NEW_OUTGOING_CALL";


    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void onDestroy() {
        Log.d("service", "destroy");

        super.onDestroy();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d("StartService", "TService");
        final IntentFilter filter = new IntentFilter();
        filter.addAction(ACTION_OUT);
        filter.addAction(ACTION_IN);
        this.registerReceiver(new CallReceiver(), filter);
        return super.onStartCommand(intent, flags, startId);
    }

    private void startRecording() {
        File sampleDir = new File(Environment.getExternalStorageDirectory(), "/TestRecordingDasa1");
        if (!sampleDir.exists()) {
            sampleDir.mkdirs();
        }
        String file_name = "Record";
        try {
            audiofile = File.createTempFile(file_name, ".amr", sampleDir);
        } catch (IOException e) {
            e.printStackTrace();
        }
        String path = Environment.getExternalStorageDirectory().getAbsolutePath();

        recorder = new MediaRecorder();
//                          recorder.setAudioSource(MediaRecorder.AudioSource.VOICE_CALL);

        recorder.setAudioSource(MediaRecorder.AudioSource.VOICE_COMMUNICATION);
        recorder.setOutputFormat(MediaRecorder.OutputFormat.AMR_NB);
        recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        recorder.setOutputFile(audiofile.getAbsolutePath());
        try {
            recorder.prepare();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        recorder.start();
        recordstarted = true;
    }

    private void stopRecording() {
        if (recordstarted) {
            recorder.stop();
            recordstarted = false;
        }
    }


    public abstract class PhonecallReceiver extends BroadcastReceiver {

        //The receiver will be recreated whenever android feels like it.  We need a static variable to remember data between instantiations

        private int lastState = TelephonyManager.CALL_STATE_IDLE;
        private Date callStartTime;
        private boolean isIncoming;
        private String savedNumber;  //because the passed incoming is only valid in ringing


        @Override
        public void onReceive(Context context, Intent intent) {
//        startRecording();
            //We listen to two intents.  The new outgoing call only tells us of an outgoing call.  We use it to get the number.
            if (intent.getAction().equals("android.intent.action.NEW_OUTGOING_CALL")) {
                savedNumber = intent.getExtras().getString("android.intent.extra.PHONE_NUMBER");
            } else {
                String stateStr = intent.getExtras().getString(TelephonyManager.EXTRA_STATE);
                String number = intent.getExtras().getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
                int state = 0;
                if (stateStr.equals(TelephonyManager.EXTRA_STATE_IDLE)) {
                    state = TelephonyManager.CALL_STATE_IDLE;
                } else if (stateStr.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)) {
                    state = TelephonyManager.CALL_STATE_OFFHOOK;
                } else if (stateStr.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
                    state = TelephonyManager.CALL_STATE_RINGING;
                }


                onCallStateChanged(context, state, number);
            }
        }

        //Derived classes should override these to respond to specific events of interest
        protected abstract void onIncomingCallReceived(Context ctx, String number, Date start);

        protected abstract void onIncomingCallAnswered(Context ctx, String number, Date start);

        protected abstract void onIncomingCallEnded(Context ctx, String number, Date start, Date end);

        protected abstract void onOutgoingCallStarted(Context ctx, String number, Date start);

        protected abstract void onOutgoingCallEnded(Context ctx, String number, Date start, Date end);

        protected abstract void onMissedCall(Context ctx, String number, Date start);

        //Deals with actual events

        //Incoming call-  goes from IDLE to RINGING when it rings, to OFFHOOK when it's answered, to IDLE when its hung up
        //Outgoing call-  goes from IDLE to OFFHOOK when it dials out, to IDLE when hung up
        public void onCallStateChanged(Context context, int state, String number) {
            if (lastState == state) {
                //No change, debounce extras
                return;
            }
            switch (state) {
                case TelephonyManager.CALL_STATE_RINGING:
                    isIncoming = true;
                    callStartTime = new Date();
                    savedNumber = number;
                    onIncomingCallReceived(context, number, callStartTime);
                    break;
                case TelephonyManager.CALL_STATE_OFFHOOK:
                    //Transition of ringing->offhook are pickups of incoming calls.  Nothing done on them
                    if (lastState != TelephonyManager.CALL_STATE_RINGING) {
                        isIncoming = false;
                        callStartTime = new Date();
                        startRecording();
                        onOutgoingCallStarted(context, savedNumber, callStartTime);
                    } else {
                        isIncoming = true;
                        callStartTime = new Date();
                        startRecording();
                        onIncomingCallAnswered(context, savedNumber, callStartTime);
                    }

                    break;
                case TelephonyManager.CALL_STATE_IDLE:
                    //Went to idle-  this is the end of a call.  What type depends on previous state(s)
                    if (lastState == TelephonyManager.CALL_STATE_RINGING) {
                        //Ring but no pickup-  a miss
                        onMissedCall(context, savedNumber, callStartTime);
                    } else if (isIncoming) {
                        stopRecording();
                        onIncomingCallEnded(context, savedNumber, callStartTime, new Date());
                    } else {
                        stopRecording();
                        onOutgoingCallEnded(context, savedNumber, callStartTime, new Date());
                    }
                    break;
            }
            lastState = state;
        }

    }

    public class CallReceiver extends PhonecallReceiver {

        @Override
        protected void onIncomingCallReceived(Context ctx, String number, Date start) {
            Log.d("onIncomingCallReceived", number + " " + start.toString());
        }

        @Override
        protected void onIncomingCallAnswered(Context ctx, String number, Date start) {
            Log.d("onIncomingCallAnswered", number + " " + start.toString());
        }

        @Override
        protected void onIncomingCallEnded(Context ctx, String number, Date start, Date end) {
            Log.d("onIncomingCallEnded", number + " " + start.toString() + "\t" + end.toString());
        }

        @Override
        protected void onOutgoingCallStarted(Context ctx, String number, Date start) {
            Log.d("onOutgoingCallStarted", number + " " + start.toString());
        }

        @Override
        protected void onOutgoingCallEnded(Context ctx, String number, Date start, Date end) {
            Log.d("onOutgoingCallEnded", number + " " + start.toString() + "\t" + end.toString());
        }

        @Override
        protected void onMissedCall(Context ctx, String number, Date start) {
            Log.d("onMissedCall", number + " " + start.toString());
//        PostCallHandler postCallHandler = new PostCallHandler(number, "janskd" , "")
        }

    }

}

inside TService class you will find CallReceiever class that is going to handle everything you need from the call. You can add parameters as per your will, but, the main point is important.

From your MainActvitiy call Service that will start your Receiever. If you want to record media from receiever directly, you will get errors, so, you need to register Receiever from service. After that, you can call start recording and end recording wherever you like. Calling return super.onStartCommand(intent, flags, startId); will have that Service lasting for more than one call, so keep that in mind.

Finally, AndroidManifest.xml file:

<manifest
    package="your.package.name"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:installLocation="internalOnly">

    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.READ_PHONE_STATE"/>
    <uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS"/>
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
    <uses-permission android:name="android.permission.WAKE_LOCK"/>
    <uses-permission android:name="android.permission.MODIFY_PHONE_STATE"/>
    <uses-permission android:name="android.permission.RECEIVE_SMS"/>
    <uses-permission android:name="android.permission.READ_SMS"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.STORAGE" />

    <application
        android:name=".AppController"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity android:name=".ui.StartActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

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

        <receiver
            android:name=".io.boot.DeviceAdminReciever"
            android:permission="android.permission.BIND_DEVICE_ADMIN" >
            <meta-data
                android:name="android.app.device_admin"
                android:resource="@xml/my_admin" />
            <intent-filter>
                <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
                <action android:name="android.app.action.DEVICE_ADMIN_DISABLED" />
                <action android:name="android.app.action.DEVICE_ADMIN_DISABLE_REQUESTED" />
            </intent-filter>
        </receiver>

        <service android:name=".io.calls.TService" >
        </service>
    </application>

</manifest>

So, this is it, it's working perfectly with my Samsung Galaxy s6 Edge+, Ive tested it on Galaxy Note 4 and on Samsung J5, a big thank you to the authors of this post and the post about receiving phone calls.

The accepted answer is perfect, except it does not record outgoing calls. Note that for outgoing calls it is not possible (as near as I can tell from scouring many posts) to detect when the call is actually answered (if anybody can find a way other than scouring notifications or logs please let me know). The easiest solution is to just start recording straight away when the outgoing call is placed and stop recording when IDLE is detected. Just adding the same class as above with outgoing recording in this manner for completeness:

private void startRecord(String seed) {
        String out = new SimpleDateFormat("dd-MM-yyyy hh-mm-ss").format(new Date());
        File sampleDir = new File(Environment.getExternalStorageDirectory(), "/TestRecordingDasa1");
        if (!sampleDir.exists()) {
            sampleDir.mkdirs();
        }
        String file_name = "Record" + seed;
        try {
            audiofile = File.createTempFile(file_name, ".amr", sampleDir);
        } catch (IOException e) {
            e.printStackTrace();
        }
        String path = Environment.getExternalStorageDirectory().getAbsolutePath();

        recorder = new MediaRecorder();

        recorder.setAudioSource(MediaRecorder.AudioSource.VOICE_COMMUNICATION);
        recorder.setOutputFormat(MediaRecorder.OutputFormat.AMR_NB);
        recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        recorder.setOutputFile(audiofile.getAbsolutePath());
        try {
            recorder.prepare();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        recorder.start();
        recordstarted = true;
    }


    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(ACTION_IN)) {
            if ((bundle = intent.getExtras()) != null) {
                state = bundle.getString(TelephonyManager.EXTRA_STATE);
                if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
                    inCall = bundle.getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
                    wasRinging = true;
                    Toast.makeText(context, "IN : " + inCall, Toast.LENGTH_LONG).show();
                } else if (state.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)) {
                    if (wasRinging == true) {

                        Toast.makeText(context, "ANSWERED", Toast.LENGTH_LONG).show();

                        startRecord("incoming");
                    }
                } else if (state.equals(TelephonyManager.EXTRA_STATE_IDLE)) {
                    wasRinging = false;
                    Toast.makeText(context, "REJECT || DISCO", Toast.LENGTH_LONG).show();
                    if (recordstarted) {
                        recorder.stop();
                        recordstarted = false;
                    }
                }
            }
        } else if (intent.getAction().equals(ACTION_OUT)) {
            if ((bundle = intent.getExtras()) != null) {
                outCall = intent.getStringExtra(Intent.EXTRA_PHONE_NUMBER);
                Toast.makeText(context, "OUT : " + outCall, Toast.LENGTH_LONG).show();
                startRecord("outgoing");
                if ((bundle = intent.getExtras()) != null) {
                    state = bundle.getString(TelephonyManager.EXTRA_STATE);
                    if (state != null) {
                        if (state.equals(TelephonyManager.EXTRA_STATE_IDLE)) {
                            wasRinging = false;
                            Toast.makeText(context, "REJECT || DISCO", Toast.LENGTH_LONG).show();
                            if (recordstarted) {
                                recorder.stop();
                                recordstarted = false;
                            }
                        }
                    }


                }
            }
        }
    }

The answer of pratt is bit uncomplete, because when you restart your device your app will working stop, recording stop, its become useless.

i m adding some line that copy in your project for complete working of Pratt answer.

<receiver
        android:name=".DeviceAdminDemo"
        android:permission="android.permission.BIND_DEVICE_ADMIN">
        <meta-data
            android:name="android.app.admin"
            android:resource="@xml/device_admin" />

        <intent-filter>
            <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
            <action android:name="android.app.action.DEVICE_ADMIN_DISABLED" />
            <action android:name="android.app.action.DEVICE_ADMIN_DISABLE_REQUESTED" />
            <action android:name="android.intent.action.BOOT_COMPLETED" />
            <category android:name="android.intent.category.HOME" />
        </intent-filter>
    </receiver>

put this code in onReceive of DeviceAdminDemo

@Override
public void onReceive(Context context, Intent intent) {
    super.onReceive(context, intent);

    context.stopService(new Intent(context, TService.class));
    Intent myIntent = new Intent(context, TService.class);
    context.startService(myIntent);

}