Android incoming call detector

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.sample.broadcastreceiver">

    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.READ_CALL_LOG" />

    <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>
    </application>

</manifest>

CallReceiver.java

package com.chronotechlabs.broadcastreceiver;


import android.content.Context;
import android.util.Log;

import java.util.Date;

public class CallReceiver extends PhonecallReceiver {
    private static final String TAG = "com.testing.firewall";
    public static String incoming_number;

    public void onIncomingCallStarted(Context ctx, String number, Date start) {
        incoming_number = number;
        Log.d(TAG, "Incoming call from: "+ incoming_number);
    }
}

MainActivity.java

package com.sample.broadcastreceiver;

import android.Manifest;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.telecom.Call;

public class MainActivity extends AppCompatActivity {

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

    @Override
    protected void onStart() {
        super.onStart();
        int phoneReadStatePermission = getApplicationContext().checkSelfPermission("READ_PHONE_STATE");
        int readCallLogPermission = getApplicationContext().checkSelfPermission("READ_CALL_LOG");
        Boolean hasPhoneReadStatePermission  = phoneReadStatePermission == PackageManager.PERMISSION_GRANTED;
        Boolean hasReadCallLogPermission = readCallLogPermission == PackageManager.PERMISSION_GRANTED;

        if (!hasPhoneReadStatePermission || !hasReadCallLogPermission) {
            this.requestPermissions(new String[]{
                    Manifest.permission.READ_CALL_LOG,
                    Manifest.permission.READ_PHONE_STATE},
                    1);
            this.registerPhoneReceiver();
        } else {
            this.registerPhoneReceiver();
        }
    }

    void registerPhoneReceiver() {
        CallReceiver handler = new CallReceiver();
        IntentFilter filter = new IntentFilter();
        filter.addAction("android.intent.action.PHONE_STATE");

        registerReceiver(handler, filter);
    }
}

PhonecallReceiver.java

package com.sample.broadcastreceiver;

import java.util.Date;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.telephony.TelephonyManager;

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 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 void onIncomingCallStarted(Context ctx, String number, Date start){}
    protected void onOutgoingCallStarted(Context ctx, String number, Date start){}
    protected void onIncomingCallEnded(Context ctx, String number, Date start, Date end){}
    protected void onOutgoingCallEnded(Context ctx, String number, Date start, Date end){}
    protected 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;
                onIncomingCallStarted(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);
                }
                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;
    }
}