How do I use NetworkTables' SubTables?

[irvingc]

The TableViewer application does not use NetworkTable objects exclusively, there's quite a bit of back-end.

You know the names of your subsystems; is there a reason you can't just use ITable.getBoolean("NAME_HERE")?

[Aero]

Originally Posted by irvingc

The TableViewer application does not use NetworkTable objects exclusively, there's quite a bit of back-end.

You know the names of your subsystems; is there a reason you can't just use ITable.getBoolean("NAME_HERE")?

I could, but it's kind of annoying to have to edit the driver station program every time I add or remove a subsystem. I'd much prefer dynamicism

[fovea1959]

Once you connect, you can call NetworkTableClient.getEntryStore().list() to get a list of all the existing key names in your client's copy of the table.

A listener will give you updated keys and values as they come in, so even if you don't get all the existing key names when you first connect, you'll be able to build a complete list of keys pretty quickly if you are sending them out in periodic().

[fovea1959]

I just reread your post, and something hit me...

Where are you trying to see what values are in the table? The FRC Driver Station software, the dashboard, or another team-written program running on the driver station PC?

[fovea1959]

...and I just checked, and dumping the keys at the beginning is unnecessary. When you connect, it appears you get update events for every existing value in the table, so you can just set up a listener and watch the names and values stream in...

[Aero]

Originally Posted by fovea1959

...and I just checked, and dumping the keys at the beginning is unnecessary. When you connect, it appears you get update events for every existing value in the table, so you can just set up a listener and watch the names and values stream in...

Awesome! We're using a custom piece of software for the client-side, as the SmartDashboard didn't really offer what we were looking for. Is there any example code for adding an ITableListener (I think that's what I want, not sure)? I can probably figure it out tonight, but I'm just wondering.
Thanks again!

[fovea1959]

super straightforward: I implemented ITableListener, then called networkTableClient.addTableListener (this, true).

If you need to see connections and disconnections, implement IRemoteConnectionListener, and call networkTableClient.addTableListener(this,true).

of course, you can have different objects for your listener (so you wouldn't use this), but hopefully you'll get the gist of it.

your valueChanged() can be a little tricky: you could get back an array or just a single variable of unknown type, and you don't know ahead of time what it will be. I had a few instance operators in there to sort stuff out. For display purposes, this worked nice:

if (o instanceof Object[]) {
 for (Object o1 : (Object[]) o) {
  sb.append("\t");
  sb.append(o1.toString());
 } else {
 sb.append("\t");
 sb.append(o.toString());
}

You *could* also get the type by going back to the client.getEntryStore().getEntry(name).getType(), but I didn't need it. I did grab client.getEntryStore().getEntry(name).getSequenceN umber() so I could see if we had updates that didn't get to the client (this is from our telemetry receiver).