Minecraft World Loaded Detection Using Redstone (Save file load detection)

minecraft-commandsminecraft-java-editionminecraft-redstone

I've been trying to search for an answer to this question for some time now
(World Load Detection / Chunk Load Detection / Join World / etc)

However, despite my effort, I've been unable to find a solution…

Details:

This is a single-player world, NOT a private or public server
The use of command blocks is acceptable
It needs to activate when I open the world, but only once
- (and every time the save is loaded, but only once)
It is a 1.15 save file

I found a lead on this reddit post: https://www.reddit.com/r/technicalminecraft/comments/7vr2gz/worldchunk_loaded_detector/

This also seemed promising but I couldn't quite follow…
https://www.minecraftforum.net/forums/minecraft-java-edition/redstone-discussion-and/commands-command-blocks-and/2828667-custom-join-message

However, the solution appears to be outdated (1+ year ago) and no longer works in version 1.15

Does anyone have any ideas?

I've tried the /tag and /scoreboard approach but those only seem to work on servers (local or public) since the command blocks will be running regardless of players being on the server
With this being a local save (and not a server), that does not appear to work.

Best Answer

With commands it's easy:

/scoreboard objectives add leave custom:leaveGame

This ticks up once for every time you leave the world, so it can be detected on the next server tick (when you have joined again). I do not know how it behaves when Minecraft is killed or crashes.

Example usage:

/execute if entity @a[scores={leave=1..}] run say The world was reopened.
/scoreboard players reset * leave

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Minecraft – Implement Random Access with Redstone

So here's an idea (and I haven't tested it yet, but hear me out): you put a minecart on a line of powered rails with some power source on them all (nearby redstone blocks, torches, whatever). This rail travels past all your locations. When you want to get to a certain place, you use a command block with /setblock to replace the powered rail at your desired location with a solid block, and the one in front of it with an unpowered rail. Then push your cart--you'll continue down the rail until you hit the new wall and stop when you get to your destination. To reset it, you can just fill the rail row with powered rails again (using the replace parameter to only replace unpowered rails and your stopping block, for safety); then push the cart back to the start (which, by the way, the first rail should have no constant power source and only be powered when you want to access something).

Or, if you want an auto-reset, you could even use setblock to spawn a command block above your stopping block which tests for the presence of a nearby cart, run that into AND gate with another (always-present) block which tests for the presence of a nearby player and inverts that, and when the output turns on, run the reset circuit (which would /tp the cart to the beginning again, fill the track up with powered rails, and clear out the new command block).

Maybe there's a more efficient way of doing this, but I think it should at least work.

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