Building an Android App: Create a Feature

Two prompts. This is where the app that only opens in Create the Project becomes one that does something.

Coming back later?

If the computer was restarted, reconnect the phone or restart the emulator first — a change is only visible after it is installed on a device.

Step 1 — Add a feature

This is the part you came for. Name all three layers — the data layer that stores things, the connecting layer, and the screen you look at. Leave one out and you get a screen with nothing behind it.

You do not have to know what those layers are called. The project writes its own instructions down, so point the agent at them instead:

Say this

Read apps/android/AGENTS.md first and follow the conventions in it, then show me your plan before changing anything. I want a product management screen: I should be able to add, edit and delete products, and it should work in both languages. List every file you changed when you are done.

What you should see: roughly ten changed files. If the list has fewer than six, something was skipped — say "you missed a layer, check the conventions file again and finish it."

Open the app on the device and try the new action yourself. A screen that renders but errors the moment you press its button is the usual sign of a half-wired layer.

Two habits worth keeping:

Habit	Why
Always ask for the plan first	one sentence to correct a plan, an afternoon to unpick bad code
One change at a time	mixing three features into one change makes it impossible to undo just the broken one

Step 2 — Write it down

Say this

Write up how the product screen works as an internal note.

What you should see: the note under .docs/. That folder is private and is never published anywhere.

If it lands in docs/content/ instead, the agent just put your private notes on a public website. Say: "move that file to .docs/ — it is not for the public site."

When the feature works and is written down, the app is finished. Next: Package It.