# From idea to running Android app

Source: https://olef.dev/docs/build/first-app

Start with one useful screen and one complete interaction. Your coding agent creates the app; Olef lets it run, see, and check what it built. You can use a local emulator or Olef Cloud.

## Before you start

You need a coding agent such as Codex or Claude Code, [Olef connected to it](https://olef.dev/docs/start/agents), and a [local or cloud environment](https://olef.dev/docs/start/environments). Creating and building an Android project needs an Android toolchain in the chosen environment. Olef Cloud provides that toolchain for its managed workflow.

## 1. Describe a small, useful app

Open an empty project folder in your coding agent, or use your Cloud workspace. Try this prompt:

```text
Build a simple Android packing-list app in Kotlin and Jetpack Compose.
I want to add an item, mark it packed, and delete it. Save the list on the
device so it is still there when I reopen the app. Start with one screen,
no login, and no backend. Use Olef to run and inspect it in my selected
Android environment. Ask me about any missing setup before assuming it
is available.
```

Replace the idea with something you actually want. A timer, checklist, or personal notes app is a good first scope. Give the agent a specific behavior to complete before adding more screens.

## 2. Get the first version running

Ask the agent to build the project and show it on the emulator:

```text
Run the app and show me its first screen. Confirm that it launches without
a crash. If the build or launch fails, use the actual error to fix it and
try again.
```

With a compatible plugin, ask it to show the live device viewer. You can try the app yourself while the agent watches the same device. Let one person or agent drive at a time.

## 3. Try the main interaction

Add “Phone charger,” mark it packed, then close and reopen the app. You should see the item and its packed state preserved.

Ask the agent to verify the same outcome:

```text
Check that I can add Phone charger, mark it packed, and reopen the app
without losing it. Inspect the actual app with Olef. Show what you tested,
what passed, and anything you could not verify.
```

A successful build is only the first check. The screen and saved behavior are the evidence that your idea works.

## 4. Make one change at a time

```text
Add an Unpacked filter so I can focus on items I still need. Keep the
saved list behavior. Run the app and verify both the filter and that
previous items remain after reopening it.
```

Small changes make it easier to notice what improved and what broke. See [Try it & make changes](https://olef.dev/docs/build/iterate) for feedback and recording workflows.

## What you have now

A working Android app, editable source code, and a behavior you have tried on a device. Ask the agent to explain where the project is saved and how to run it again.

:::note[Publishing is a separate step]
Olef does not yet provide an end-to-end Play Store publishing toolchain. This walkthrough ends with a running development app. Signing, release preparation, and Play Store submission remain separate tasks.
:::

## If you get stuck

Describe what you expected and what you saw. Ask the agent to use Olef's screen, logs, and crash diagnostics before changing code. For environment failures, use [troubleshooting](https://olef.dev/docs/troubleshooting).