Blog de conocimiento gratuito: linux, programación, open source, bases de datos, android, frameworks, web e informática en general.

Imprimir códigos QR en impresora térmica

How to print QR codes on Thermal printer

Summary: In this post I will show you how to print readable QR codes on a thermal printer (also called ticket printer, pos printer, etc.) using JavaScript and a plugin.

If you have followed my posts, you will know that a long time ago I developed a plugin and I have added new features, until today we print QR codes on a thermal printer.

Some time ago I showed you how to print a ticket /receipt directly from browser, today we will use it to print a QR code.

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By parzibyte, ago

PHP & MySQL tutorial using PDO

Although there are millions of tutorials about MySQL and PHP, I decided to make mine but in a very very simple way. Before you start, you must have a basic knowledge in MySQL.

MySQL and PHP connection using PDO

Source code of PHP file connection

It is worth mentioning that we will not see good practices of databases, relationships, etc. We will use the tables as they are, without looking at normalization, or things like that.

Note: this tutorial uses PDO, but remember that we can also use mysqli functions. Personally I recommend PDO, because it is object oriented. However, I hope to write a tutorial about mysqli in the future.

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By parzibyte, ago
MySQL and PHP connection using PDO
How does the plugin for thermal printers work

A plugin for printing in thermal printers directly from browser

In this post I will introduce to you a plugin for printing tickets, receipts or invoices on a thermal printer using client-side JavaScript even if your web page or application is on a cloud server.

This plugin allows you to print directly from browsers, without dialogs and without browsers compatibility issues because you only have to send a HTTP request to print silently and in the background.

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By parzibyte, ago

Print receipt in thermal printer using JavaScript, CSS & HTML

In this post I will show you how to print a ticket or receipt by using JavaScript (client side) and a thermal printer. At the end we will have a great ticket that looks like this:

Ticket sample

Receipt printed in thermal printer using JavaScript only

Obviously you can change the font family, size, logo and so on. And remember: we will be using only pure CSS, HTML & JavaScript, no frameworks; though you can use any framework to render the content before printing.

You can see the demo here, and the full code on my GitHub.

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By parzibyte, ago
Ticket sample
Diálogo con layout personalizado en Android

Custom alert dialog in Android

Dialog and AlertDialog with custom layout on Android

In this post I will show you how to create custom dialog on Android using a layout created by us, that is, create a custom alert by adding elements such as EditText, Button, etc.

Custom alerts on Android serve to display an alert that is not a confirmation alert, since we can define a custom layout.

To achieve this we will use the Dialog and AlertDialog.Builder classes.

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By parzibyte, ago

How to redirect in Spring Boot

Redirect in the Spring Boot framework

In this post I will show you how to redirect or direct the user to another URL within the method of a controller in the Spring Boot framework.

Redirecting to another URL in Spring Boot is very useful when the user does a certain action and we must return it to the main page.

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By parzibyte, ago

Change express-generator app port

The express-generator package helps a lot in the development of web applications with Node, because it generates the skeleton of an application.

A small disadvantage is that, when generating the code, we do not know how to change some very basic things, for example, the port on which the app listens (the default port is 3000).

In this post I will show you how to change the port in some app generated by express-generator. (more…)

By parzibyte, ago

How to install Node.js and NPM on Android using Termux app

In this post we will see how to install Node.Js and NPM (Node package manager) in Android.

At the end we will be able to run Node.js applications as if we had a Linux server.

We will also see how to install dependencies using the npm install command, since it is a possible thing in Android thanks to Termux.

Specifically we will install version 6.9.0 of NPM and version 12.3.1 of node, although perhaps when you read this post you will install a newer version.

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By parzibyte, ago
5 - Insertar datos y probar base de datos

How to install MySQL (MariaDB) on Android with Termux

Install MySQL on Android

Android mobile devices are not designed to be servers (although some of them are powerful), however it is always interesting to see how technology advances and day by day we can do more things with our phones.

Today we will see how to install the MySQL or MariaDB server on Android, thanks to the Termux application. For that it is enough to execute a few simple commands and voila, we will have a MySQL database server in our Android; fully functional and ready to execute queries.

If we want to put it for production, we can do it as long as we configure security. In short, we will not see more advanced topics; we will only see how to install mysql on Android.

Here we will use MariaDB and MySQL as synonyms; that is, if you see that I say MariaDB do not get confused, I mean MySQL; and vice versa.

I know that there are really more differences especially with the licenses, but that is another topic and you can search it in Google if you wish.

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By parzibyte, ago