BaseActivity.java

public class BaseActivity extends AppCompatActivity {
    // Variable Declarations
    private AudioManager mAudioManager;
    private TelephonyManager mTelephonyManager;
    private static final String = "MUTE_STATUS";
    protected SharedPreferences mSharedPrefs;
    protected boolean muteSound;
    final String TAG = "mute";
    // UI Declarations
    private MenuItem mMuteMenuItem;

    private PhoneStateListener phoneStateListener = new PhoneStateListener() {
        @Override
        public void onCallStateChanged(int state, String incomingNumber) {
            if (state == TelephonyManager.CALL_STATE_RINGING) { //Incoming call: Pause music
                Toast.makeText(BaseActivity.this, "INCOMING CALL", Toast.LENGTH_SHORT).show();
                Log.v(TAG, "INCOMING CALL");
                onPhoneCallInterrupt();
            } else if (state == TelephonyManager.CALL_STATE_IDLE) {
                //Not in call: Play music
                Log.v(TAG, "NOT IN A CALL");
            } else if (state == TelephonyManager.CALL_STATE_OFFHOOK) { //A call is dialing, active or on hold
                Log.v(TAG, "CALL IS ACTIVE!");
                Toast.makeText(BaseActivity.this, "DIALING", Toast.LENGTH_SHORT).show();
                onPhoneCallInterrupt();
            }
        }

    };

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

        setVolumeControlStream(AudioManager.STREAM_MUSIC);
        mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
        mTelephonyManager = (TelephonyManager) getSystemService(TELEPHONY_SERVICE);

        // Recommend storing this in shared preferences and loading from there
        mSharedPrefs = getSharedPreferences("Whatever", MODE_PRIVATE);
        muteSound = getMuteStatus();

        // Setup UI items
        mMuteMenuItem = (MenuItem) findViewById(R.id.muteMenu);
        updateMuteMenuItem();
    }

    public boolean getMuteStatus() {
        muteSound = mSharedPrefs.getBoolean(MUTE_STATUS, false);
        return muteSound;
    }

    @Override
    protected void onResume() {
        super.onResume();
        tManager.listen(phoneStateListener, PhoneStateListener.LISTEN_CALL_STATE);
    }

    @Override 
    protected void onPause() {
        tManager.listen(phoneStateListener, PhoneStateListener.LISTEN_NONE);
        super.onPause();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_base, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.muteMenu:
                changeMuteStatus();
                break;
        }
        return super.onOptionsItemSelected(item);
    }

    protected void changeMuteStatus() {
        if (getMuteStatus()) { 
            unMute();
        } else { 
            mute();
        }
    }

    protected void setMuteStatus(boolean muted) {
        mSharedPrefs.edit().putBoolean(MUTE_STATUS, muted).apply();
        muteSound = muted;
    }

    protected void updateMuteMenuItem() {
        // Just to be safe null check
        if(mMuteMenuItem == null) {
            return;
        }

        // if we are muted display unmute and vice versa
        if(getMuteStatus()) { 
            mMuteMenuItem.setTitle("UNMUTE");
        } else {
            mMuteMenuItem.setTitle("MUTE")
        }
    }

    protected void unMute() {
        setMuteStatus(false);
        mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, userVolumeOnStart.userVolume, 0);
        
        updateMuteMenuItem();

        Toast.makeText(this, "UNMUTED", Toast.LENGTH_SHORT).show();
        Log.v(TAG,"UNMUTED");
    }

    protected void mute() {
        setMuteStatus(true);
        userVolumeOnStart.userVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_RING);
        mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, 0, 0);

        updateMuteMenuItem();

        Toast.makeText(this, "MUTED", Toast.LENGTH_SHORT).show();
        Log.v(TAG,"MUTED");
    }

    protected void stopTimer() {
        Log.v(TAG, "Timer Stopping");
        TwentySeconds.stopTimer();
    }

    protected void onPhoneCallInterrupt() {
        Log.v(TAG, "Phone Call Interruption");
        
        // Stop the timer
        stopTimer();

        // If we are unmuted mute
        if(getMuteStatus()) {
            changeMuteStatus();
        }

        if(this instanceOf Main_Menu.class) {
            // Do nothing we are already in main menu
        } else {
            Intent i = new Intent(this, Main_Menu.class);
            startActivity(i);
        }
    }

}