wear-compose-m3

name	wear-compose-m3
description	使用 Wear OS Compose Material3 的专家指导。当创建、更新或迁移 Wear OS 项目时使用。涵盖 androidx.wear.compose.material3、androidx.wear.compose.foundation、androidx.wear.compose.navigation3，以及 AppScaffold、ScreenScaffold、TransformingLazyColumn 和 ambient mode 等核心组件与概念，也包括从 Material 2.5 和 Horologist 等早期版本迁移。
license	Complete terms in LICENSE.txt
metadata	{"author":"Google LLC","last-updated":"2026-07-08","keywords":["Wear OS","Compose","Material3","Horologist","TransformingLazyColumn","AppScaffold","ScreenScaffold"]}

Prerequisites and compatibility

1. Current Wear OS Compose version in-use: To find the installed library version, read gradle/libs.versions.toml or build.gradle.kts directly. Don't run ./gradlew dependencies or other shell commands to resolve versions.
2. Wear OS Compose Material3 version: If an internal tool is available to establish the latest stable version {VERSION} of androidx.wear.compose:compose-material3, use that tool.
   • Otherwise, fetch the official Maven metadata XML to identify {VERSION} (highest number, ignoring -alpha, -beta, or -rc).
3. Strict compliance: If a version is listed as stable, you MUST use it, unless overridden by the user. Do not downgrade based on initial "Unresolved reference" errors in the editor or outdated web search results.
4. Kotlin version: For Wear Compose Material3, use Kotlin 2.0.0 or higher.
5. Compose compiler:
   • If Kotlin version is 2.0.0+ , the project must use the org.jetbrains.kotlin.plugin.compose Gradle plugin.
   • If Kotlin version is < 2.0.0 , the project must use kotlinCompilerExtensionVersion in composeOptions, matching the Compose to Kotlin Compatibility Map.
6. Min SDK: Ensure minSdk is at least 25.
7. Sample extraction mandate: Wear Compose libraries ship with an additional JAR file which contains individual samples for each and every component. You mustn't propose code changes, other than previews or basic changes such as color changes, until the samples in Capability 3 are extracted to the local cache. Library source files are incomplete and NOT a substitute for these samples; bypassing extraction is an environment setup failure.

Gotchas

1. Mandatory sync and validation: After updating versions in libs.versions.toml or build.gradle.kts, you must perform a Gradle sync before refactoring any code. This ensures the environment has resolved the libraries correctly.
2. Prohibition of guessing (error protocol): If you encounter an 'Unresolved Reference' or API mismatch after a successful sync, do not attempt to 'fix' it by downgrading the library version.

Capabilities and tools

Capability 1: Migration

Use this guidance when migrating from an older version of Wear OS Compose or Horologist.

1. Unless otherwise indicated by the developer, use the latest stable version of Wear Compose Material3 from {VERSION}.
2. Read the migration guide.
3. Use the official component mappings from the migration guide.
4. Before refactoring any component (for example, Chip -> Button), check the parameter names, slot types, and "Expressive" design tokens.
5. Do not use the Horologist Composables, Compose Layout, or Compose Material libraries.
6. Always check against the component guidance in Capability 4.
7. Expect screenshot tests to fail when a migration has been performed: Even when migrating to very similar components, expected defaults for padding and positioning will have changed. Do not seek to artificially match the pre-migration screenshot, but give preference to the Material3 defaults.

Capability 2: Adding Wear OS Compose Material3 features or updating the app

Use this guidance when the developer asks to update a project which is using an earlier version of Wear OS Compose Material3, or when they ask to add further features.

1. Unless otherwise indicated by the developer, use the latest stable version of Wear Compose Material3 from {VERSION}.
2. Do not use the Horologist Composables, Compose Layout, or Compose Material libraries.
3. Always check against the component guidance in Capability 4.
4. Expect screenshot tests to fail when a migration has been performed: Even when migrating to very similar components, expected defaults for padding and positioning will have changed. Do not seek to artificially match the pre-migration screenshot, but give preference to the Material3 defaults.

Capability 3: Component samples

Wear Compose includes individual component samples for each and every component, within the <artifact>-<version>-samples-sources.jar file. Gradle automatically downloads these JAR files along with the main library JAR when using any of compose-material3, compose-foundation or compose-navigation3.

Use the canonical component samples whenever adding or adjusting a Wear Compose Material3 component.

STRICT COMPLIANCE: Extraction is NOT optional. You are FORBIDDEN from implementing any code until samples are extracted and read. Bypassing this step with alternative search tools or by assuming library documentation is sufficient is a protocol breach. You MUST verify the local cache by reading a sample file before proceeding.

Exception: You don't need to extract samples if the request is strictly related to tooling (for example, adding @WearPreviewDevices), updating text/colors, or basic refactoring that doesn't involve adding new Wear Compose components.

Step 1: Prepare

1. Check the build.gradle.kts or libs.versions.toml to ensure the Wear Compose version matches {VERSION}.
2. Ensure that the necessary dependencies are downloaded by doing a Gradle sync.

Step 2: Check the local cache

1. Define the cache directory path: /tmp/wear-compose-samples/{VERSION}/. Do NOT choose your own different location.
2. Check if this directory exists and contains subdirectories with .kt files.
   • IF YES (cache hit): Proceed to Step 4.
   • IF NO (cache miss): Proceed to Step 3.

Step 3: Network-based sample retrieval

Google Maven publishes a -samples-sources.jar alongside every library release. Download and extract it directly without needing a local Gradle sync or cache lookup.

1. Determine the {VERSION} of androidx.wear.compose:compose-material3 from build.gradle.kts or libs.versions.toml.

2. Define {ARTIFACT} as the items in the list ["material3", "foundation"]. Also include navigation3 if androidx.wear.compose.navigation3 is used.

3. For each {ARTIFACT}, run the following commands to download and extract the samples:

   # Download the samples-sources JAR
   curl -sSL "https://dl.google.com/dl/android/maven2/androidx/wear/compose/compose-{ARTIFACT}/{VERSION}/compose-{ARTIFACT}-{VERSION}-samples-sources.jar" -o {ARTIFACT}-{VERSION}-samples.jar
   
   # Extract and flatten into the cache directory
   unzip -q -o {ARTIFACT}-{VERSION}-samples.jar -d /tmp/wear-compose-samples/{VERSION}/{ARTIFACT}/
   
   # Clean up
   rm {ARTIFACT}-{VERSION}-samples.jar
   

4. If this works, proceed directly to step 4.

Step 4: Read samples and implement

1. Read the relevant .kt sample files.
2. Use these official, version-matched samples as the source of truth for:
   • Required parameters and slot names.
   • Default styling and typography tokens.
   • Interactive behaviors (for example: onClick, onLongClick).
   • Component nesting (for example: AppScaffold -> ScreenScaffold).

Capability 4: Component guidance

Mandatory: Use this capability as a checklist against any component use. It provides more holistic guidance on how to use each component in practice, beyond the component syntax.

1. AppScaffold and ScreenScaffold

   • [ ] Use AppScaffold as the outer container, with ScreenScaffold children.
   • [ ] Use only ONE AppScaffold and any number of ScreenScaffold.

2. ScalingLazyColumn - Use TransformingLazyColumn instead.

3. TransformingLazyColumn - You will need the following imports:

   import androidx.wear.compose.foundation.lazy.TransformingLazyColumn
   import androidx.wear.compose.foundation.lazy.TransformingLazyColumnDefaults
   import androidx.wear.compose.foundation.lazy.rememberTransformingLazyColumnState
   // ...
   import androidx.wear.compose.material3.lazy.rememberTransformationSpec
   import androidx.wear.compose.material3.lazy.transformedHeight
   

   
   

   Canonical example:

   val columnState = rememberTransformingLazyColumnState()
   val transformationSpec = rememberTransformationSpec()
   ScreenScaffold(
       scrollState = columnState
   ) { contentPadding ->
       TransformingLazyColumn(
           state = columnState,
           contentPadding = contentPadding
       ) {
           item {
               ListHeader(
                   modifier = Modifier
                       .fillMaxWidth()
                       .transformedHeight(this, transformationSpec)
                       .minimumVerticalContentPadding(ListHeaderDefaults.minimumTopListContentPadding),
                   transformation = SurfaceTransformation(transformationSpec)
               ) {
                   Text(text = "Header")
               }
           }
           // ... other items
           item {
               Button(
                   modifier = Modifier
                       .fillMaxWidth()
                       .transformedHeight(this, transformationSpec)
                       .minimumVerticalContentPadding(ButtonDefaults.minimumVerticalListContentPadding),
                   transformation = SurfaceTransformation(transformationSpec),
                   onClick = { /* ... */ },
                   icon = {
                       Icon(
                           imageVector = Icons.Default.Build,
                           contentDescription = "build",
                       )
                   },
               ) {
                   Text(
                       text = "Build",
                       maxLines = 1,
                       overflow = TextOverflow.Ellipsis,
                   )
               }
           }
       }
   }
   

   
   
   • [ ] Use TransformingLazyColumn instead of ScalingLazyColumn.
   • [ ] You must pass the contentPadding parameter from ScreenScaffold to the TransformingLazyColumn.
   • [ ] Use the minimumVerticalContentPadding modifier to achieve required padding top and bottom.
     • This expects a value from defaults, such as ButtonDefaults, CardDefaults, `ListHeaderDefaults.
     • Note: This is a scoped modifier available within TransformingLazyColumnItemScope.
   • [ ] Ensure the list morphs and scales.
   • [ ] Use transformedHeight modifier.
   • [ ] Use transform = SurfaceTransform(...).
   • [ ] If configuring a list for snapping, use flingBehavior and rotaryScrollableBehavior together:

   val columnState = rememberTransformingLazyColumnState()
   ScreenScaffold(scrollState = columnState) { contentPadding ->
       TransformingLazyColumn(
           state = columnState,
           flingBehavior = TransformingLazyColumnDefaults.snapFlingBehavior(columnState),
           rotaryScrollableBehavior = RotaryScrollableDefaults.snapBehavior(columnState)
       ) {
           // ...
           // ...
       }
   }
   

   
   

4. ScreenScaffold

   • [ ] Guard the scrollIndicator with !LocalScrollCaptureInProgress.current.

5. EdgeButton

   • [ ] Do NOT use as the final item within a TransformingLazyColumn. Instead, use the slot in ScreenScaffold.
   • [ ] When used in a TransformingLazyColumn, add the required overscroll behavior:

   val columnState = rememberTransformingLazyColumnState()
   ScreenScaffold(
       scrollState = columnState,
       edgeButton = {
           EdgeButton(
               onClick = { /* TODO */ },
               modifier = Modifier.scrollable(
                   columnState,
                   orientation = Orientation.Vertical,
                   reverseDirection = true,
                   // Apply overscroll to the EdgeButton for proper scrolling behavior.
                   overscrollEffect = rememberOverscrollEffect(),
               )
           ) {
               Text("More")
           }
       }
   ) { contentPadding ->
       TransformingLazyColumn(
           contentPadding = contentPadding,
           state = columnState,
       ) {
           // ...
           // ...
       }
   }
   

   
   

6. Column

   • [ ] USE as a direct child of ScreenScaffold if the screen is will never scroll, even with the largest system font.
   • [ ] Use TransformingLazyColumn instead for all other cases.

7. Styles

   • [ ] Do NOT hard-code text sizes, use typography from MaterialTheme.
   • [ ] Do NOT hard-code colors, use colorScheme from MaterialTheme.

8. Use component defaults:

   • [ ] Components such as Button have a corresponding ButtonDefaults object.
   • [ ] Check for and use the *Defaults object for any component when working with padding and styling values, in preference to hard-coded values.

9. Use Wear specific previews:

   • [ ] WearPreviewDevices
   • [ ] WearPreviewFontScales

10. Ambient mode

    • [ ] Use LocalAmbientModeManager instead of AmbientLifecycleObserver.

11. Navigation

    • [ ] When adding navigation fresh, use Navigation3.
    • [ ] For Navigation3 in Wear OS, use SwipeDismissableSceneStrategy() from the Wear Compose compose-navigation3 library.

12. Comments

    • [ ] Where any Kotlin file has been modified, ensure that the existing comments are up to date and accurately reflect any changes to the implementation.

13. HorizontalPager or VerticalPager

    • [ ] Use the Composable hierarchy in this order: AppScaffold, HorizontalPagerScaffold, HorizontalPager, AnimatedPage, ScreenScaffold. Or similarly for VerticalPager.