programming

How to Use Textwatcher in Android

The Android framework provides the EditText interface element to allow the entry and editing of text. There are some use cases where one might need to detect text changes as they are typed in the EditText and react accordingly. One use case could be showing auto suggest values. The TextWatcher interface can be used for listening in for changes in text in an EditText. This interface has three abstract methods -  afterTextChanged(Editable s) beforeTextChanged(CharSequence s, int start, int count, int after) onTextChanged(CharSequence s, int start, int before, int count) Wiring the TextWatcher to the EditText If you take a look at EditText’s documentation, you won’t see any obvious way to wire the TextWatcher to it.

How to Use Datepicker in Flutter

Its not too tough, really. We are going to create a very simple project to demonstrate the use of the datepicker, in particular the material datepicker. Suggested readings Flutter for Beginners: An introductory guide to building cross-platform mobile applications with Flutter and Dart 2 Beginning App Development with Flutter: Create Cross-Platform Mobile Apps Lets see how its going to look. It just consists of a text and an icon button.

Writing A On Update Trigger in Postgresql

The previous article was about deletion trigger. This article is about update triggers. I had two tables what_did_you_eat and what_was_the_type. On insertion into what_did_you_eat, the what_type column was populated with the food type. what_did_you_eat column namedatatype what_did_you_eat_idserial whattext what_was_the_type column namedatatype what_was_the_type_idserial what_did_you_eat_idint what_typetext Now, if I update the value in what column of a row from what_did_you_eat, I would want the corresponding row in what_was_the_type table to be updated too.

Writing a On Delete Trigger in Postgresql

The previous article was about insertion trigger. I had two tables what_did_you_eat and what_was_the_type. On insertion into what_did_you_eat, the what_type column was populated with the food type. what_did_you_eat column namedatatype what_did_you_eat_idserial whattext what_was_the_type column namedatatype what_was_the_type_idserial what_did_you_eat_idint what_typetext Now, if I delete a row from what_did_you_eat, I would not want a row to remain in what_was_the_type to refer to a non existing row in the what_did_you_eat table.

Writing A On Insert Trigger In Postgresql

Here is a simple example of a on insert postgresql trigger. I have a table called what_did_you_eat. It has the following structure - column namedatatype what_did_you_eat_idserial whattext what will contain what was eaten. I have another table called what_was_the_type with the following structure - column namedatatype what_was_the_type_idserial what_did_you_eat_idint what_typetext I want to store the type of food that was eaten in what_type column. And I want to do this to happen on insert into the what_did_you_eat table.

How To Parse Json In A Stored Procedure In Postgresql

Say we have a table called person with the following structure --------------------------- column| datatype --------------------------- _id | autonumber name | text age | integer --------------------------- We want to insert multiple records into the table using a stored procedure. If we have a stored procedure with say two input variables name and age, then it will take multiple calls. We can do this using a single call if we use a json input and using the json_to_recordset function.

Three Tier Architecture in Docker

In this article I am going to talk about how to do a classic 3-tier architecture using docker containers. The 3-tiers will be: Frontend tier: This will host the web application. Middle tier: This will host the api, in our case the REST api. Database tier: This will host the database. We want to expose the web application to the outside world. Simultaneously, we want this layer to be able to talk with the middle tier only not the database tier.

Upgrading Postgresql to V11

I run two instances of postgres servers - one on my local machine and the other one on my do virtual machine. Both of them are on debian. One of them was running 10.x and the other one 9.x version of postgres. I wanted to upgrade them to the latest version - that is version 11. I was pleasantly surprised to see how simple it was. This is what I did:

Creating an OTP Screen in Flutter

Nowadays, one time password (OTP) is used a lot as an authentication mechanism. Sometimes the OTP is sent using SMS and sometimes its sent through email. A screen for users to input the OTP has to be created. In this article we will talk about creating a simple screen in flutter to allow users to enter the OTP. Suggested readings Flutter for Beginners: An introductory guide to building cross-platform mobile applications with Flutter and Dart 2

Writing a Postgresql Stored Procedure Returning a Single Value

Say we have a table called person with the following structure --------------------------- column| datatype --------------------------- _id | autonumber name | text age | integer --------------------------- We want to write a stored procedure to return the highest age that we have in the table. We will use OUT param here. CREATE OR REPLACE FUNCTION get_max_age(OUT max_age int) RETURNS int LANGUAGE 'plpgsql' AS $BODY$ BEGIN SELECT MAX(age) INTO max_age FROM person; END $BODY$; That’s it.