Android New Module

Overview

This skill helps you create new Android gradle modules following Mozilla's conventions and structure. Components are organized into categories: browser, concept, feature, lib, service, support, ui, and compose.

Component Categories

• browser - High-level browser components (engine, menu, state, etc.)
• compose - Jetpack Compose components
• concept - Abstract API contracts and interfaces
• feature - Feature modules for browser functionality
• lib - Standalone libraries (utilities, tools)
• service - Services (push, sync, etc.)
• support - Support/utility modules
• tooling - Support modules for the build or tools.
• ui - UI components; has overlap with Compose components.

Steps to Create a New Component

Create a plan to execute the steps. The plan should include all nine steps below.

1. Determine Component Type and Name

Ask the user:

• What category? (feature, lib, browser, etc.)
• What should it be named? (lowercase with hyphens, e.g., my-component)
• What will it do? (for description)
• Will it be published to Maven? (most are publish: true, examples are publish: false)

2. Create Directory Structure

mkdir -p mobile/android/android-components/components/{category}/{name}/src/main/java/mozilla/components/{category}/{name}
mkdir -p mobile/android/android-components/components/{category}/{name}/src/test/java/mozilla/components/{category}/{name}
mkdir -p mobile/android/android-components/components/{category}/{name}/src/test/resources

3. Create build.gradle

Reference the example at mobile/android/android-components/components/feature/example/build.gradle for the standard structure.

Key elements:

• Apply plugins: com.android.library and kotlin-android
• Set namespace: mozilla.components.{category}.{name}
• Include common dependencies: androidx.core.ktx, kotlinx.coroutines
• Include test dependencies: junit.bom, junit4, robolectric, kotlinx.coroutines.test
• Apply common config and publish scripts

Add dependencies as needed:

• Support base (for LifecycleAwareFeature): implementation project(':components:support-base')
• Lifecycle: libs.androidx.lifecycle.runtime
• Compose: Add platform(libs.androidx.compose.bom) and compose dependencies
• State management: implementation project(':components:lib-state')
• Browser state: implementation project(':components:browser-state')
• Other components: implementation project(':components:{category}:{component-name}')

4. Create AndroidManifest.xml

File: src/main/AndroidManifest.xml

<!-- This Source Code Form is subject to the terms of the Mozilla Public
   - License, v. 2.0. If a copy of the MPL was not distributed with this
   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
<manifest />

5. (Optional) Create Main Kotlin Source

File: src/main/java/mozilla/components/{category}/{name}/{ComponentName}.kt

Reference the example at mobile/android/android-components/components/feature/example/src/main/java/mozilla/components/feature/example/ExampleFeature.kt.

Key elements for a feature component:

• MPL 2.0 license header
• Package: mozilla.components.{category}.{name}
• Implement LifecycleAwareFeature for lifecycle-aware features
• Use dependency injection for testability (e.g., inject CoroutineDispatcher)
• Include coroutine scope for async operations
• Override lifecycle methods (start(), stop())

For simpler library components, a basic class with the necessary methods is sufficient.

6. (Optional) Create Test File

File: src/test/java/mozilla/components/{category}/{name}/{ComponentName}Test.kt

Reference the example at mobile/android/android-components/components/feature/example/src/test/java/mozilla/components/feature/example/ExampleFeatureTest.kt.

Key elements:

• MPL 2.0 license header
• Use StandardTestDispatcher from kotlinx.coroutines.test for testing coroutines
• Inject the test dispatcher into the component being tested
• Use runTest(testDispatcher) to run tests with coroutine support
• Use testDispatcher.scheduler.advanceUntilIdle() to advance virtual time
• Track actual callback invocations instead of using mocks
• Write descriptive test names using backticks (e.g., `start triggers onUpdate callback`)
• Use JUnit assertions to verify behavior

7. Create Robolectric Configuration

File: src/test/resources/robolectric.properties

sdk=35

This configures Robolectric to use Android SDK 35 for unit tests.