BaseActivity.java

public class BaseActivity extends AppCompatActivity {
    private AudioManager mAudioManager;
    private TelephonyManager mTelephonyManager;
    private boolean muteSound;
    final String TAG = "mute";
    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
        muteSound = false;
    }

    public boolean isMuted() {
        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:
                if (isMuted()) { //If it's odd UNMUTE
                    unMute(item);
                } else { //If its even MUTE
                    mute(item);
                }
        }
        return super.onOptionsItemSelected(item);
    }

    protected void unMute(MenuItem item) {
        muteSound = false;
        mAudioManager.setStreamVolume(AudioManager.STREAM_MUSIC, userVolumeOnStart.userVolume, 0);
        
        item.setTitle("MUTE");

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

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

        item.setTitle("UNMUTE");

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

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

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

        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);
        }
    }

}