How to detect call state Android

AndroidManifest.xml

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

PhonecallReceiver.java

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
//https://developer.android.com/reference/android/telephony/TelephonyManager.html
  
private static int lastState = TelephonyManager.CALL_STATE_IDLE;
private static Date callStartTime;
private static boolean isIncoming;
private static String savedNumber;  //because the passed incoming is only valid in ringing


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

    //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();
                onOutgoingCallStarted(context, savedNumber, callStartTime);                     
            }
            else
            {
                isIncoming = true;
                callStartTime = new Date();
                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){
                onIncomingCallEnded(context, savedNumber, callStartTime, new Date());                       
            }
            else{
                onOutgoingCallEnded(context, savedNumber, callStartTime, new Date());                                               
            }
            break;
    }
    lastState = state;
}
}