Creating the project

We are not going to create the project from scratch like we did in the Basic Java tutorial. Since the project requires a lot of setup and support files, the easiest way is to copy another project as a template. The project we are going to copy is the RobotIterative project. It would be nice if there were a nice Eclipse wizard to create the project, but in lieu of that, I have created a small Java project called CreateRobotProject which we can use to make a workable copy of the RobotIterative project and then we can import that new project into Eclipse.

To run this program, double click on the CreateRobotProject.jar file in the workspacePi2017 folder which should display the following dialog box.

RobotJavaCreateProjectDialog

In the Project Name field, enter the name of your new project (e.g. JohnsRobot) and leave the Template field set to RobotIterative. Then click the Create button. If all goes well, it should create a project named with the name you gave.

Once the project has been created, go back to eclipse and choose the File / Import command:

RobotJavaFileImport

Which will bring up the following dialog:

RobotJavaFileImportDialog1

Open the General options and choose the Existing Projects into Workspace option as shown then click Next.

RobotJavaImportDialog2

Then click on the Browse button and choose your MyProject folder which should be in your workspace:

RobotJavaBrowseForFolder

Click OK and this should take you back to the Import dialog with the root directory field set:

RobotJavaImportDialog3

Click Finish and your project should be Package Explorer panel on the life.

There is one thing more that we must check before we continue. The version of Java that is running on the robot is 1.7 and we must make sure that we build our project with that version or it will not be able to run. To check this, choose the Preferences option from the Window menu:

WindowPreferences

Then in the Preferences dialog, open the Java item on the left and click on Compiler and make sure that the Compiler compliance level is set to 1.7 as shown below:

prefencesdialog

Now open up your project and double click on the Robot.java file to load it into the editor.

RobotJavaMyRobotProject

Our project has now been created and imported and we are ready to learn how to run it on our robot.

Your program consists of a ‘Robot’ class which inherits from the built in ‘IterativeRobot’ class. Let’s take a look and try and understand the structure of this class:

The first thing we see is the declaration of two variables, m_exampleSubsystem, and m_OI.  We are going to be using FRC’s Command based system for this program. To use this system, we create classes which inherits from the class Subsystem.  Each of these classes that we create will handle a specific subsystem of the robot. For example we will have a subsystem to handle the drive motors.  In this program we have an example of a subsystem called ExampleSubsystem which we will used as a model when we create our custom subsystems. Later we will look into the details of how these subsystems work when we create the subsystems needed for our Robot.

The next line creates declares a variable of the class OI. This class is used to bind buttons on a controller (e.g. a joystick) to commands that will control the robot.  Later we will see exactly how this is done.

Note that neither m_exampleSubsystem nor m_OI are initialized at this point.  We need to wait to do this until the robot is initialized.  We will create instances of these variables later in the robotInit function.

Finally, we have the constructor for the class. Once again, we need to be careful as to what we initialize in this constructor.  Many elements that we may wish to use should not be instantiated this early in the process.  Instead, we should wait for the robotInit function to be called, which brings us to the next code snippet:

The robotiInit function will be called once after the internals of the robot are initialized.  This is where most of your initialization should take place and we instantiate instances of our ExampleSubsystem and OI classes.  Note that like our main Robot class, you need to be careful what things you initialize in other classes which may be created before the robot has been initialized.

Next we see a set of six functions which are used to control the three modes of the robot, Autonomous, Teleop, and Test.

The comments in the code are pretty self explanatory.  Each of the modes has a function (e.g. autonomousInit) which is called when that mode starts.  Then, as long as the robot stays in that particular mode, that mode’s ‘periodic’ function (e.g. autonomousPeriodic) will be repeatedly called.

Finally, we see the following code:

This is the main entry point for our program.  Here we instantiate our main Robot class, and call the Start function provided by the inherited IterativeRobot class, which starts our robot running.

Before we move on, I would like to bring your attention the the numerous calls to Logger.Log(…).  This is a debugging function which allows you to add logging to your program.  This can be most useful when trying to figure out why your program is not behaving the way you expect. Later we will see how we can control what information is logged and what is not.  I strongly suggest that you make use of this feature when writing your code.  It can make finding an elusive problem much easier later, especially when the problem only manifests itself when running the robot in competition.

Next: Running the program

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