Short source code examples

As a note to self, I just used this code to delete rows from a JavaFX TableView in a Scala application:

As a note to self, I used code like this in a Scala + JavaFX application to add a ContextMenu to a TableView:

As a quick note to self, this is how you add an ActionEvent EventHandler to a MenuItem in JavaFX, when writing JavaFX code in Scala:

As a quick note today, if you’re working on a Scala project and get a compiler error message like this:

As a brief note to self, I just created a “spacer” in JavaFX using a Region, as shown in this code:

// a spacer to push the visible elements up a little
val spacer = new Region
VBox.setVgrow(spacer, Priority.ALWAYS)

I originally created the spacer as a Separator, which is the wrong thing (it’s more like an HTML <hr> tag). A JavaFX Region just gives you a blank space, which you can control as needed.

If you ever need to create a Dialog in LibGDX, I can confirm that this example code works:

I just started working with LibGDX, so I don’t know if there’s a better way to create a LibGDX Scene2d ImageButton, but I can confirm that this approach works:

Texture hikeTexture = new Texture(Gdx.files.internal("hike_btn.jpg"));
Texture hikeTexturePressed = new Texture(Gdx.files.internal("hike_btn_pressed.jpg"));
hikeButton = new ImageButton(
    new TextureRegionDrawable(new TextureRegion(hikeTexture)),
    new TextureRegionDrawable(new TextureRegion(hikeTexturePressed))
hikeButton.setPosition(60, 300);  //hikeButton is an ImageButton

I currently use this code in the show() method of a class that implements Screen, and it works as desired.

If you ever wanted to use Scala with Java Swing classes (like JFrame, JTextArea, JScrollPane, etc.), the process is pretty seamless. Here’s an example of a simple Scala/Swing application where I show a text area in a JFrame:

As a quick note, here’s a little Java graphics utilities class I started putting together today. Mostly I’m just concerned with monitor/display sizes at the moment, especially when a computer system has multiple displays.

In production code I recommend that you use a good “Files” library like Apache Commons IO, but if you want to create your own Scala FileUtils class, here’s some source code that can help you get started.

First, here’s some code for the FileUtils class (an object, technically):

Here’s some source code for a Scala method that reads a text file that may have comments into a List[String]:

Here’s a quick Scala example that shows how to convert multiple spaces in a string to a single space:

I’m putting this Scala shell script out here as a “source code snippet” so I can find it again if I need it. This file reads an input file that contains a series of HTML <h1> tags. I use this as part of a process of publishing an Amazon Kindle ebook from an HTML file, and in one of the steps of the creation process, I use this script to help create the Table of Contents (TOC) for the book.

Here’s the source code:

As a quick note, if you ever need to call the invokeLater of the Java SwingUtilities class in Scala, you can pass it an anonymous function (lambda) like this:

SwingUtilities.invokeLater(() => {
    // your gui-updating code here, such as:
    for (c <- newsControllers) c.updateContent()

(I haven’t worked with Java 8 lambdas too much, but I assume that the Java lambda syntax is similar to that.)

Because I think it’s often best to “learn by example,” I’ve become a connoisseur of SBT build.sbt examples, and this build.sbt file from Lihaoyi’s PPrint project demonstrates a lot of SBT variables:

As a quick example of how to use a Thread with a basic Handler in an Android application, the following code creates a view where the text in the TextView is updated to show the current date and time when the Button is tapped.

Java source code

First, here’s the Java source code for a file class named ThreadHandlerActivity:

I am working on a way to rapidly mock up Android applications using Android Studio, i.e., to rapidly prototype Android applications on the fly, and little snippets of code help to make this happen. For instance, this snippet of code shows how to show a popup dialog to prompt a user to enter information into a text field:

As I learned recently, the Mac/Java AppBundler tool is a little out of date these days, but you can still use it with Java 8 and MacOS 10.12 to build Mac/Java applications. One problem you can run into is getting this ugly Info.plist error:

If you’re using the Oracle AppBundler to build a Mac/MacOS application bundle from a Java application and run into this error when running Ant:

NoSuchFileException: <directory path here> Info.plist

I have found that the problem is that I have not set and exported JAVA_HOME. To set and export JAVA_HOME on MacOS 10.12, I use this command in the shell script I use to build my Mac/Java app:

To show an Android Snackbar message from an Activity or Fragment, use Java code like this:

Snackbar.make(view, "going to: " + url, Snackbar.LENGTH_LONG).show();

One key is to remember to call the show() method after make(). I have a tendency to forget to call show() and then wonder why my Snackbar message isn’t showing up. So maybe a better way to show that code is like this: