searching lessons

The 694 FIRST robotics team is doing history webcasts. During today’s Joe and Seth were talking about how there used to be a “Looking Forward” post where 694 was listed as a favorite for the Hartford competition for the first time in 2009. Joe did a quick search and learned it was hard to find.

Since he was doing the webcast, he said he’d look later. I decided to look while I listened. It was hard. Here’s what I dd:

composite builds in gradle

In the lab today, I got a nice Gradle question. I’m answering it here on the blog so all the students can see it. (and anyone else who is curious).

The use case

We have a common library that this year (and all future year’s robots should use). However, this is the first year of competition with the library so it is likely we will need to make changes to it and rebuild at competition.

Constraint #1 – lack of wifi

For any professionals reading this wondering why we don’t use Jitpack, github or any other hosting – internet is “tricky” at competition.; It is common for there to not be any wifi in the pit and you aren’t allowed to make your own hotspot. So we need a solution that works without internet and easily lets us re-build on the same machines.

Constraint #2 – reuse

I really want the library (StuyLib) to stay in it’s own repository and not have the build file “polluted” by any changes. Why you ask? So it stays a library and not something we copy/paste from year to year.

The solution

Composite builds. Gradle has a nice system for composite builds that lets you refer to one build from another.

Directory structure

  • git clone
  • git clone (or any other robot)
  • That means StuyLib and fantastic-spork are in parallel directories

Updates to StuyLib

Yes, I know, I said I didn’t want updates. The only things I added were a group and version variable. That gives the artifact a proper name. (group id = com.stuypulse, artifact id = StuyLib, version = 1.0.0). StuyLib still doesn’t know it is part of a composite build.

plugins {
   id "java"
   id "edu.wpi.first.GradleRIO" version "2020.1.2"

// add the following two lines
group = 'com.stuypulse'
version = '1.0.0'

sourceCompatibility = JavaVersion.VERSION_11
targetCompatibility = JavaVersion.VERSION_11

Updates to Robot

At end of settings.gradle, add this line:

includeBuild '../StuyLib'

Then in build.gradle, add a dependency on StuyLib

def ROBOT_MAIN_CLASS = "com.stuypulse.robot.Main"

// add a dependency
dependencies {


First, I tested that I could build each independently:

  1. cd StuyLib
  2. ./gradlew build
  3. cd ..
  4. cd fantastic-spork
  5. ./gradlew build

Then I added a class that used existing functionality in StuyLib to fantastic-spork

package jb;

import com.stuypulse.stuylib.util.*;

public class Jeanne {
  StopWatch s;
//  String str = StopWatch.TEST;

I re-ran the ./gradlew build in fantastic-spork and good. Then I added one line to StopWatch:

public static final String TEST = "test";

I uncommented the line in Then for the key part. I re-ran ./gradlew build in fantastic-spork and it worked. I was able to recompile fantastic-spork and have it see a change in StuyLib without having to rebuild StuyLib.

Plus this change to StuyLib only exists on my machine which proves it is being used.

FRC using VS Code and Eclipse together for WPILIb programming

I’ve tried using VS Code. I enjoy uisng it for things like JavaScript, Python and Markdown. With Java, I feel like I’m hitting my head against the wall. I’m too used to a “full powered IDE” so an editor makes me aware of what I rely on. (I tried IntelliJ as well and that felt productive easily.)

The nice thing is that 2019 FRC projects are “just” gradle projects. So there is no reason I can’t use both VS Code and Eclipse together! VS Code for creation a new project and deploying. Eclipse for virtually everything else.

Creating a project from VS Code

Just like when I was first trying VS Code, creating a WPILib project is easy. Just like the screensteps say!

  1. Click “W” icon in top right
  2. Choose template for a new project
  3. Choose Java
  4. Choose command based project (or whatever you prefer)
  5. Enter directory – this can be the same directory for all projects since they each get their own folder.
  6. Enter project name
  7. Enter team number
  8. Click generate project

Importing the Project in Eclipse

Since the project is just a Gradle project, you can import it into Eclipse

  • File > Import
  • Existing Gradle Project
  • Enter the root directory that the project is in. For example suppose your directory was “frc” and project name was “NewRobotProject”. Then the root directory would be “…/git/frc/NewRobotProject”. In other words, the directory with your build.gradle file.
  • Click Finish
  • Wait a minute or two. The bottom right will say “Synching Gradle project workspace”. It will show the percentage as the import occurs.

Editing in Multiple IDEs/Editors

At this point, you have a normal Eclipse project.   All the features and keyboard shortcuts from Eclipse are there. For example, open a command and click on the super class name (Command.) Press F3 and it takes you right to the source code. Eclipse knows where it is because Gradle told it.

If you edit in multiple tools, you just need to know how to refresh from disk in each one.

In Eclipse, right click the project and choose refresh. (Or click F5)

In VS Code,mouse over the project name and choose the circle refresh arrow.

Deploying the Project from VS Code

Since the VS Code and Eclipse projects are pointing at the same directory, you only have one project. This means you can simply:

  1. Click “W” icon in top right
  2. Choose “Deploy Robot Code” from the menu