Javier Menendez – Page 12 – Xojo Programming Blog

Canvas: How to Create Custom UI Controls

Canvas: How to Create Custom UI Controls

Published April 15, 2019 by Javier Menendez

Xojo includes a good amount of UI controls available from the Library for Desktop, Web, iOS and Raspberry Pi targets. These are the pieces that allow you to layout the user interface of your apps: properties, methods and events that, when combined, define the specific behavior of the project at hand.

Sometimes, subclassing the available controls is the answer to add specific behaviors you need. But what happen when none of the controls offer what you need, whether visually or functionally? The answer is the Canvas class (for Desktop projects), WebCanvas class (for Web projects) and iOSCanvas class for iPhone and iPad devices. But how do you create your own UI controls from scratch? Read on to learn…

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Tip: How To Deal with A Lot of Columns in Database Tables

Published March 28, 2019 by Javier Menendez

Most of the time, the access to our databases tables involves a small amount of columns (fields), so the use of the Field method of the RecordSet class is the most practical approach to retrieve the selected columns values. But what can we do when the query returns, for example, dozens of columns we need to get values from?

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How To Speed Timers in Windows

Published March 18, 2019 by Javier Menendez

The Timer and Xojo.Core.Timer classes gives us a resolution that is more than enough for most of the cases where we need to use them. In fact, under macOS we don’t find any kind of limitation when using the classes provided by the Xojo Framework: we can achieve a maximum resolution of 1 ms on any of the most recent computers.

But when working with Windows OS this is not so straightforward . It doesn’t matter if we try to set the Timer Period property to a minimum value of 1 ms; Windows imposes a minimum resolution of 16 ms, insufficient when we demand the maximum precision for a critical task (period interval between Timer firings).

Of course Xojo has a solution for this, you can resort to a third-party plug-in that works extremely well … or you might find the following technique useful for all kinds of projects.

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Control Sets and ContainerControl: A New Approach

Published March 8, 2019 by Javier Menendez

A Control Set is the feature to use when there are several instances in a Window’s layout and you need to command (or access them) from code, both for those available by default in the Framework and ones based on your own graphic classes. For example, this allows us to invoke a method in a concrete instance, based on its control index, or invoke the same method to all of them (iteration). All of this without knowing in advance, at runtime, how many of such instances are placed in the layout.

An inconvenience of this feature is that you can’t use it when the graphic controls are placed on a ContainerControl due to the way ContainerControls are implemented. The good news is that this problem has an easy solution! Read on to learn about it:

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Tip: SQLite in RAM … to improve speed!

Published February 11, 2019 by Javier Menendez

It’s very usual to use encrypted SQLite databases in our Xojo projects where we expect to get the maximum read speed from them. But the truth is that encrypting the data in these databases can introduce a penalty in our queries, both from read and writing/updating data to them. How can we improve this? One technique is the creation of a new in-memory based SQLite database, where we will be able to copy the table (or tables) we are interested in getting the maximum speed possible with. Continue reading to see how to do this.

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Recursion: Emptying a Folder

Published February 4, 2019 by Javier Menendez

Do you need code to delete the files and folders from the selected folder? In that case, there is a technique I propose to you and that is based on recursion. That is, the ability of a function to call itself repeatedly until the task is complete; in this case, the function will call itself every time it detects a new folder/directory inside the designated original folder/directory.

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Web: Create Sliding-Animated Menus

Published January 30, 2019 by Javier Menendez

Sometime ago a Xojo user asked if it is possible to use Xojo Web to create the kind of animated menus seen in several regular websites. After some investigation (and the invaluable help of Greg O’Lone), the answer is: yes, you can do that! If you are interested in seeing how to achieve this, continue reading!

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Animating the Web: Fading Images in-out

Published December 19, 2018 by Javier Menendez

This tutorial will show you how easy it is to create animations on components of Xojo web apps, thanks to the use of the Style Editor and the WebAnimator class. Learn how to do a fade effect between two images that you can expand and adapt to your web apps.

In order to recreate this fade effect we’ll mainly use a couple of styles (WebStyle class) to set the initial status for each one of our images (instances from the WebImageView class). These will be overlaped in the web page, sharing the same position. Then we’ll add a button to the web page so it will fire the animation every time it is clicked.

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Web Services Part II: Xojo Web, at your service

Web Services Part II: Xojo Web, at your service

Published November 8, 2018 by Javier Menendez

In a previous entry we started to dig into web services with Xojo. The first post focused on the backend (server side), creating the Xojo app acting as middleware between the clients and the database that holds your data. We are using SQLite as the backend engine but it would not be difficult to change to other supported database engines like PostgreSQL, MySQL (MariaDB), Oracle or SQL Server, and even ODBC; all of these are supported by Xojo!

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Tutorial: Saving WebCanvas Images to Disk

Published October 11, 2018 by Javier Menendez

The WebCanvas control is used for drawing graphics in web apps. It takes advantage of the HTML5 Canvas making it fast and powerful. Sometimes is can be useful to be able to save the graphics drawn in the WebCanvas to an image file, but unfortunately there is no built-in Xojo method to do this.

However, by using a little JavaScript you can easily add this capability to Xojo.

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Author: Javier Menendez