Xojo 2019R2 has a lot of new features and enhancements, including the simplification of updating the User Interface in apps from threads running in combination with the main app thread. Doing that in previous releases required the use of a thread in combination with a Timer, for example.
Comments closedAuthor: Javier Menendez
As an Object Oriented Programming language (OOP), Xojo’s data types, especially the non-primitive ones, use or can use a Class hierarchy. This means that one class, either included by default in the Xojo Framework or created from scratch, can act as a base or root class for other classes based upon them.
Comments closedIf you’re starting to program with Xojo, then you’ll probably soon find yourself in a situation where you need to use one of the Container types: Array. In this case, it’s also probable that you might be confused at first as to why you don’t get what you expected when assigning the contents of a source Array to a target Array via the assignment operator (“=”).
Comments closedHow to save pictures in a database is without doubt one of the more frequent questions I’m asked about. I hear this from Xojo newcomers,…
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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…
Comments closedMost 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?
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.
Comments closedA 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:
Comments closedIt’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.
Comments closedDo 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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