ActivityとFragmentのリアルタイム通信

    if (handler != null) {
        new Thread(new Runnable() {
            @Override
                public void run() {
                    /*  Fragment */
                    Message message = new Message();
                    Bundle bundle = new Bundle();
                    bundle.putInt("customer_count", customer_count);
                    message.setData(bundle);
                    handler.sendMessage(message);
                }
            }).start();
        } else {
            Log.d("handler", " ");
    }

public void setHandler(android.os.Handler handler) {
        this.handler = handler;
}

// Activity 
    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            Bundle bundle = msg.getData();
             // 
            int customer_count = bundle.getInt("customer_count");
            // 
            if (personal_custom_count != null && personal_custom_icon != null) {
                if (customer_count != 0) {
                    // 
                } else {
                   // 
                }

            }
            Log.d("handler", "" + customer_count);
        }
    };

    // 
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        mainActivity = (MainActivity) context;
        mainActivity.setHandler(handler);
    }