如何从服务器应用程序获取通知到客户端应用程序？

Question

如何获取通知？在我的应用程序（客户端）中，我没有从服务器收到通知。实际上，我需要的是创建服务器应用程序。它包含使用recyclerview项目的订单列表。当我尝试使用contextmenu更新任何项目时，它将显示微调框包含3个值（“放置”，“途中”，“运送”）。选择并单击“是”后，将向“客户端应用”发送通知。但是我在选择订单状态时没有从服务器收到任何通知。请帮助任何人。

服务器应用

private void showUpdateDialog(String key, final Request item) {
    final AlertDialog.Builder alertDialog = new
            AlertDialog.Builder(OrderStatus.this);
    alertDialog.setTitle("Update Order");
    alertDialog.setMessage("Please Choose Status");

    LayoutInflater inflater = this.getLayoutInflater();
    final View view = inflater.inflate(R.layout.update_order_layout,
            null);
    spinner = (MaterialSpinner) view.findViewById(R.id.statusSpinner);
    spinner.setItems("Placed", "On my way", "Shipped");
    alertDialog.setView(view);
    final String localKey = key;
    alertDialog.setPositiveButton("YES", new
            DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                    item.setStatus(String.valueOf(spinner.getSelectedIndex()));

                    requests.child(localKey).setValue(item);
                }
            });

    alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
        }
    });
    alertDialog.show();
}

客户端应用

private void showUpdateDialog(String key, final Request item) {
    final AlertDialog.Builder alertDialog = new AlertDialog.Builder(OrderStatus.this);
    alertDialog.setTitle("Update Order");
    alertDialog.setMessage("Please Choose Status");
    LayoutInflater inflater = this.getLayoutInflater();
    final View view = inflater.inflate(R.layout.update_order_layout,
            null);
    spinner = (MaterialSpinner) view.findViewById(R.id.statusSpinner);
    spinner.setItems("Placed", "On my way", "Shipped");

    alertDialog.setView(view);
    final String localKey = key;
    alertDialog.setPositiveButton("YES", new
            DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                    item.setStatus(String.valueOf(spinner.getSelectedIndex()));
                    requests.child(localKey).setValue(item);
                }
            });

    alertDialog.setNegativeButton("NO", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
        }
    });
    alertDialog.show();
}